M u . 7nur. Bid., Vol. 8, 1970, pi). 21.5 -306

THE PROBLEM OF OIL POLLUTION OF THE SEA

A. NELSON-SMITH Department of Zoology, University College of Xwansea,

Swansea, Wales

I. Introduction . . .. .. .. .. .. * . 11. Sources and Control . . .. .. . . . . ..

A. Tanker Operation and General-cargo Shipping . . €3. Harbours and Marine Terminals . . . . . . C. Coastal Industry and Other Sources . . . . . .

111. Properties of Petroleum Oils .. .. .. .. A. Physico-chemical Characteristics . . .. .. B. I3ehaviour of Spilt Oil on Sea and Shore C. Detection and Identification . . . . ,. * .

IV. Effects of Oil Pollution . . . . .. . . .. A. Mode of Action and Toxicity of Oils . . .. .. B. Effects on Marine Comrnunities .. .. .. C. Carcinogenesis . . .. . . . . .. .. D. Rehabilitation of Oiled Birds . . . . .. .. E. Public Amenity and the Tourist Industry . . . .

V. Removal of Spilt Oil . . .. . . .. . . .. B. Dispersal, Sinking and Recovery at Sea . . .. C. Problems in Cleansing Shores . . .. . . ..

VI. Conclusions and Prospects . . .. . . .. ..

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A. Bacterial Degradation and Other Biological Processes

D. Mode of Action and Toxicity of Solvcnt-emulsifiers

VII. References .. .. .. . . . . . .

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I . INTRODUCTION The Report from the Select Committee on Science and Technology

(1968) points out that oil pollution is referred to (as " slime ") in the Book of Genesis and by Herodotus. Such natural seepages still occur in petroleum-producing areas, but elsewhere, oil pollution of the sea results mainly from its transport or use as a fuel by shipping. Possibly the first account of this was by Jonas Hanway who in 1754 complained of leakages from wooden petroleum-barges in the Caspian Sea (Hawkes, 1961); a century later, these barges were still creating a pollution problem on the Volga.

The first widespread use for petroleum products was in lamps, where mineral oil began t o replace vegetable or whale oil in the mid-

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nineteenth century. It was shipped in barrels carried in the hold, like whale oil or any other liquid cargo, but even so was liable to spillage as with the schooner " Thomas W. Lawson )', wrecked on the Isles of Scilly in 1907 with the loss of her cargo of two million gallons of crude oil (Parslow, 1967a). Steamers did not at first engage in the petroleum trade for fear of fire, so the first true tankers were sailing vessels fitted out with wing tanks. The Anglo-American Oil Company's " Daylight )', one of the most successful, sailed on into 1921, although the steam- tankers " Gluckauf " and " Bakuin " entered the Batoum oil-service in 1886. At much the same time, the internal-combustion engine and the steam-turbine were invented. The Royal Navy turned t o oil-firing for the turbine-driven Tribal-class destroyers in 1908, while the first sea- going motor-ship '' Vulcanus )' was launched in 1910.

Much of the early pollution of European coasts was by fuel from the bilges and bunker-tanks of oil-fired or motor ships, whose numbers were increasing rapidly. Crude oil was mostly processed in petroleum- producing regions and tankers carried the refined products, many of which were clean light oils. The shipping lanes converging on the English Channel are the busiest in the world, so that the degree of pollution already became sufficient to prompt the passage in 1922 of the Oil in Navigable Waters Act, which prohibited the discharge of oil or oily water in British territorial waters. The United States followed with the Oil Pollution Act of 1924. In 1926 an international conference in Washington recommended the establishment of coastal zones 50-150 miles wide in which the discharge of oil should be prohibited ; agreement could not be reached, but the zones were recognized voluntarily by the shipowners' associations of many Western nations. The scheme formed the basis of a Convention drawn up by the League of Nations in 1935 but after the withdrawal of Germany, Italy and Japan from the League, this Convention could not be ratified and the outbreak of war in 1939 prevented further action.

I n 1938, world petroleum production was 278 million tons ; western Europe consumed 36 million tons of oil, of which the British share was 11 million tons. Rate of consumption was enormously accelerated by the 1939-45 war and subsequent industrial expansion, until by 1967 world production had reached 1 828 million tons and Britain alone consumed 85 millions tons (Select Committee, 1968 ; British Petroleum CO., 1968). During this period, the contribution made to world production by Middle East oilfields grew from nearly 4% to over 27% (Fig. 1). By 1960, the growth of the European market and the political instability of the Middle East and other oil-producing regions made it economically and politically prudent to build refineries at the point of

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FIG. 1. Main oil shipments to western Europe-A, from 1963 to early 1967 ; R, in late 1967. The width of tho arrows is proportional to the tonnage carried. Compare with similar maps by the Ministry of Transport (1953) and IMCO (1964); after British Petroleum Review-( 1967).

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consumption. Thus not only was there a great increase in the sea- transport of oil ; there was a basic change in its nature. Large tankers entering European waters now carry crude oil, while refined products (whose spillage creates less of a pollution problem) are carried overland or in small coastal tankers.

Recent governmental efforts to control oil pollution of the sea have been reviewed in a US. State Deyt. Report (1959) and by Barclay- Smith (1958, 1967). Various meetings of naturalists and wildfowlers in 1952 were followed by the appointment of the Faulkner Committee, which reported the next year (Ministry of Transport, 1953). I n 1954 an international conference in London drew up a Convention which, like that of 1935, prohibited the discharge of oil within specified coastal zones. The United Kingdom was the first to ratify the Convention, passing the Oil in Navigable Waters Act of 1955; by 1958, having been ratified by ten nations, the Convention came into force. I ts admini- stration passed to the Intergovernmental Maritime Consultative Organization (IMCO) when that body was formed by the United Nations in 1959. The United States ratified the Convention in 1961, after a further international conference in Copenhagen.

Amendments to the 1958 Convention extending the prohibited zones (to include, for example, the entire Baltic and North Seas) and regulating further classes of vessel were proposed at an IMCO conference in 1962 and eventually came into force in 1967 (IMCO, 1962, 1967) ; but by this time " Torrey Canyon " had been stranded off the coast of Cornwall, bringing to a head the apprehension felt in many quarters about the operation of increasingly large tankers. Proposals discussed at subsequent IMCO meetings include regulations governing the con- struction, navigation and routeing of tankers as well as measures directly concerned with pollution prevention and control (Goad, 1968). Legal problems arising from the " Torrey Canyon " incident, sum- marized by Marshall (1967; see also Edwards, 1968) were discussed at, an International Legal Conference on Marine Pollution Damage con- vened by IMCO in Brussels during November 1969. Procedures were laid down by which a coastal nation might act if a casualty on the high seas threatened to cause severe pollution. A Convention was drafted placing strict liability for compensation upon the owners of an oil- carrying ship from which the cargo escapes or is discharged. As an interim arrangement, nearly 60% of the world tanker fleet had already subscribed to the TOVALOP plan, which from October 1969 provided for much of the cost of cleaning up an oil spill to be covered by the owners, encouraging them to take quick action in minimizing the resultant damage.

THE PROBLEM O F OIL POLLUTION O F THE SEA 219

11. SOURCES AND CONTROL A. Tanker operation and general-cargo shipping

The largest and most dramatic spillages of oil a t sea have resulted from the collision or stranding of tankers. It has been argued that the current trend towards very large bulk carriers should reduce this risk, because fewer voyages are necessary to keep any one refinery or tank- farm supplied. Nevertheless, in the three years ending with April 1967, 91 tankers went aground and 238 were involved in collision. 19% of the groundings and 9% of the collisions resulted in cargo spillage-a total of 39 incidents. I n the first five months of 1968, a further 39 tankers were involved in various accidents, not all resulting in oil-spills (Brockis, 1967; Select Committee, 1968). When a large tanker is damaged, it is obvious that she is potentially capable of losing a great deal of oil ; modern design trends do little to minimize this possibility. Before the 1939-45 war, typical tankers carried 10 000-12 500 tons of cargo at speeds up to 12 knots. To meet wartime demands, American shipyards went into mass-production of the T2 tanker, carrying some 16 500 tons at a sustained speed of 144 knots. For some years after the war, this type formed the backbone of tanker fleets before it was ousted by " supertankers " (as they were called in the early 1950s) of about 24 000 tons.

Tankers are constructed on a basic plan of three longitudinal series of tanks ; in the T2 and related designs, these were about 36 ft long. After the closure of the Suez Canal in 1956, even larger and faster tankers became economically desirable ; the implications of their deviation from earlier designs are reviewed in the Batelle-Northwest Report (1967). To reduce hull weight and simplify the plumbing, alternate wing-tank divisions became swash bulkheads (incomplete divisions which merely reduce cargo movement) ; in later designs this practice was extended to the centre tanks. Many recently-built vessels of 40 000-60 000 tons have tanks which are effectively 80-100 ft long. A greater capacity (and larger tanks) can be incorporated in older tankers by the process of " jumboizing ", in which a new and larger centre-section is inserted between the original bows and stern, which contain expensive machinery, crew-quarters, etc. Many T2 tankers were enlarged in this way, although the best-known example is now ( ( Torrey Canyon ", which " grew " from 67 000 to 118 000 tons. The capacity of today's '( supertankers "in the 100 000-500 000 tons range is obtained by increasing draught and breadth rather than length, so that a tank only three times as long as those in the T2 design may con- tain fifty times as much oil-the entire cargo of a pre-war tanker. Some

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dry-cargo bulk carriers of over 100 000 tons, designed for alternative oil-carrying service, lack even the longitudinal bulkheads. Doubt has been cast on the seaworthiness of some such designs if more than one compartment should be damaged. I n these circumstances, the simplifi- cation of pumping arrangements reduces flexibility in the control of cargo, while the development of better anti-corrosion treatments permits the use of thinner plating, which is less resistant to violent impacts.

Although they are capable of high speeds, all but the very largest of modern tankers still have a single screw for reasons of economy. Their manceuvrability in narrow waterways is necessarily restricted. For example, “ Torrey Canyon ” was making about 16 knots when she struck Pollard Rock and would otherwise have required at least 2 miles to come to a dead stop; other supertankers require as much as 7 miles (Wiebe, following Edwards, 1968). The turning circle of such tankers ranges from one-half to over 2 miles. Of course, modern navigation aids should compensate for this (see Kluss, 196813). Although she lacked a Decca Navigator, “ Torrey Canyon’s ” radar had a range of 40 miles. Had she been following a prescribed course, as all civil aircraft are required to do, she would have avoided disaster. Traffic separation is already observed, on a voluntary basis, in the Strait of Dover and other regions of high traffic density; its operation is dis- cussed by Dilling (1968). However, the 40 000-ton tanker “ Anne Mildred Brravig ” was rammed by a small coaster in fog off the Elbe estuary in 1966 when proceeding on a faultless course. The collision was entirely the responsibility of the coaster, yet such small craft would not be subject to the proposed controls (see Brockis, 1967). Further preventive and remedial measures are discussed in a U.S. Congress Committee Report (1967).

Measures which can be taken to control pollution after accidental damage has occurred depend, of course, on the severity of the accident. A tanker still having her own power may be able to move off towards repair facilities or the open sea and might well have surplus tank capacity into which she could pump oil from the damaged compart- ment. Even when a stranded vessel is stuck fast, it is rarely necessary to jettison oil overboard in order to avoid immediate disaster. Unfortu- nately, the value of the ship is invariably much greater than that of the cargo and current salvage contracts provide no reward for the avoidance of pollution. The possibilities of pumping the cargo into an empty tanker standing off the wreck were well demonstrated when the “ Esso Margarita ” successfully received over 15 000 tons of the 18 000 tons of fuel-oil carried by the “ General Colocotronis ”, which ran onto a

THE PROBLEM O F OIL POLLUTION O F THE SEA 221

reef in the Bahamas in March 1968 (Spooner and Spooner, 1968; Fig. 2). However, it is often impossible for vessels of suficient capacity to approach as close as this ; transfer of cargo becomes unacceptably slow, especially if the stricken tanker has lost the use of her pumps. Holds- worth (1968) and Kluss (1968b) discuss the equipment and methods

FIG. 2. “ Esso Margarita ” (foreground; 1 1 000 dwt) unloading fuel-oil from the *‘ General Colocotronis ” (18 000 dwt), stranded on a reef off Eleuthera (Bahamas). Three-quarters of her cargo was safely removed, after which she was hauled off and sunk in deep water (photo : Frederic Maura).

available for salvaging the cargo in these circumstances, but weather conditions may, in any case, make such lightening impossible. Alter- natives listed by Holdsworth include gelling, freezing and burning. Gelling is now feasible ; the material of choice is slow setting and thus does not require mixing. The process is expensive, but may be cheaper than clearing up the spill. Freezing would require a vast amount of energy and might lead to the brittle fracture of an already weakened

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hull. Burning is considered to be a last resort, since it renders the ship worthless ; experience with “ Torrey Canyon ” shows that it is possible, but requires the addition of much additional inflammable material and frequent reignition.

The compartmental construction of tankers may permit salvage of an undamaged portion by “ explosive surgery ”, using shaped plastic charges, if the fire risk can be minimized. The after half of the “Anne Mildred Brovig ” was saved in this way and, in general, it is more useful after a collision than a stranding. Once a tanker has sunk in fairly deep water, it appears that oil remaining in her is released slowly but steadily through deck vents. The U S . Coast Guard (1959) estimated that, a t the end of the Second World War, a t least 61 tankers still containing 210 million gal of oil lay along the Atlantic and Pacific coasts of the United States; but recent dives on carefully selected wrecks off the north-east Atlantic coast failed to produce even a small sample for analysis (U.S. Coast Guard, 1968). The fuel-tanks of other ships may retain their contents for longer ; the German cruiser “ Blucher ”, sunk in Oslo Fjord during April 1940, began to leak oil in June 1969.

A source of pollution from tank-shipping which is less obvious but, until recently, was much more important than accidental damage, is the need for a tanker to carry sea-water ballast on her return journey. This is usually accommodated in the oil tanks and occupies up to one-third of the cargo space. The ballast has to be discharged at the loading port as oil is taken on. Each tank contains the residues of its previous cargo ; in all 0.3-0*5% of the cargo is left behind-about 200 tons in a 50 000- ton tanker. The discharge of even a third of this amount of oil in the ballast water would not be permitted at the loading port, nor would it be practical to build shore separating facilities capable of dealing with such large volumes ; so it was normal practice to wash the tanks at sea, pumping the washings overboard and then taking ballast into the clean tanks. From recent shipping figures, this would result today in the discharge into the sea of some 6 000 tons of crude oil per day-nearly 2+ million tons per year. Fortunately, the major tanker operators introduced the “ load-on-top ” system in 1964. This is described in detail by Kluss (1968a) ; in brief, the washings are pumped to one tank (acting as a slop-tank) where the oil is separated, often by the use of demulsifying chemicals or heating coils. When separation is as nearly complete as possible, the water is pumped from below the oil and dis- charged into the ship’s wake. At the destination port, a fresh cargo is loaded on top of the recovered oil. This procedure requires care, since only a little excess salt water can be dangerous in some refining pro- cesses; it also takes time and t,rouble, although this is balanced on

THE PROBLEM O F OIL POLLUTION OF THE SEA 223

average by the value of the oil saved (Brummage et al., 1967 ; Brum- mage, 1968). The 1958 Convention set an upper limit of 100 p.p.m. oil in water discharged at sea, whereas the last of the slop-tank water reaches a concentration of 400-1 000 p.p.m. ; but the turbulence of the wake is such that in the immediately surrounding water this is reduced to 0.17 p.p.m. IMCO amended the Convention in October 1969, setting a new limit in terms of distance travelled. Sixty litres of oil per nautical mile will now be permitted which, in trials, produces no detectable slick. I n some of the latest large tankers (" Universe Ireland " and " Universe Kuwait ", for example), two wing-tanks function exclusively as ballast-tanks ; in those which will still require washing, special coatings and redesigned internal structures reduce the amount of " clingage " (see Davis, 1968).

It is probable that as many as half a million tons of persistent oils are nevertheless discharged into the sea each year (Dudley, 1969). Their source is partly tanker-operators who still do not observe proper precautions and partly shipping other than tankers. Most general- cargo ships, when sailing only partially loaded, require extra weight low down in the hull. This is usually provided by filling empty bunker- tanks in the double bottom with water which thereby becomes con- taminated with fuel oil (in addition to any other pollutants or disease organisms present in the waters of the port of origin). A typical freighter carries about 1 000 tons of ballast, which may contain up to 10 tons of oil; in 1964, 16 000 such vessels discharged their ballast water in U.S. ports alone (U.S. Department of Interior Report, 1967). Some countries require ships ballasted in this way to carry oil-water separators but this does not guarantee that they will be used and many designs are very inefficient (see Shackleton et al., 1960; Permutit Co. Report, 1966). Many depend on gravity separation, even though the density of fuel oils is often very near that of the sea in European waters and may exceed that of tropical or fresh waters (Blade, 1966).

I n any mechanically-powered vessel, particularly oil-fired or motor ships, the engine-room bilges will also become oily and may exceed the 100 p.p.m. limit. Ideally, such oily water, as well as recovered oil from separators, sludge filtered from fuel lines, and other oily wastes should be discharged to special reception facilities a t the destination port. I n most European and North American ports these exist and may even include mobile separator- or tank-barges, but in many others, facilities are inadequate or lacking (IMCO, 1964). The Faulkner Report (Ministry of Transport, 1953) points out that 1-2% of the total oil consumed escapes unburnt through the funnel of an oil-burning ship. A large vessel on the transatlantic service may burn 6 000 tons in it

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single crossing, so appreciable quantities must be deposited on the surface. Even outboard motors contribute a quantity of waste oil which in open waters is insignificant but can accumulate appreciably in enclosed bays, harbours and inland waters (English et al., 1963a, 196313 ; Dietrich, 1964).

B. Harbours and rnarine terminals

Many of the sources of oil spillage at sea, enumerated above, occur equally in port. Collisions happen with the greatest frequency in harbour approaches where the traffic is densest and other accidents may be associated with docking activities-an unusual example is the tanker ‘‘ Fina Norvege ”, which holed her forward fuel tanks with her own anchor in Plymouth Sound (see Holme and Spooner, 1968). Coastal tankers do not normally clean tanks at sea before taking on ballast, but after a short period of separation in port much of the water can nevertheless safely be discharged overboard and the small volume of oily residues remaining can usually be accepted by shore facilities. It is worth noting that in very enclosed docks, where the water is more or less static, a series of small discharges containing 100p.p.m. of oil or less can still lead to an appreciable concentration of oil in the receiving water. Under still conditions this may trap silt and other suspended matter and sink to the bottom, from which it is released to rise to the surface again after the slightest disturbance (as, for instance, in the Queen’s Dock, Swansea-Naylor, 1966).

Perhaps the commonest source of oil pollution from dry-cargo ships in port is the process of bunkering with fuel oil. This is pumped through flexible hoses which are liable to damage through wear or ship move- ment; an overlong one may fall between hull and jetty, becoming kinked or crushed, whereas too short a hose may be snatched from its couplings by sudden movements following the close passage of another vessel. Precautions which should be taken are listed by the American Merchant Marine Institute (1953). Unless each end of the hose is blanked off as soon as it is disconnected, its remaining contents are liable to drain out when it is hoisted ashore. Leakages can occur from inlets and vents, especially if the tank overflows ; any deck spills will reach the sea unless the scuppers are plugged. When the bunker-tank has been used for water ballast, the sea-cock may have been left open ; it is then possible for oil to be forced out beneath the hull, appearing as a surface slick only at some distance from the ship. A good look-out and efficient communication between pump and deck crews will avoid or minimize the more obvious forms of spillage.

At oil terminals the same comments apply. With more pipes and

THE PROBLEM O F OIL POLLUTION O F THE SEA 225

valves to handle and a far greater pumping rate, there is a considerably increased danger of pollution; on the other hand, oil-jetty and tanker crews have the advantage of training and experience. An American Petroleum Institute manual (1 964) deals with all pollution-control aspects of tanker loading and unloading operations. Dudley (1968, 1969) concludes that the major cause of oil-port pollution is human error-partly through poor communication and partly because of inattention or carelessness. I n Milford Haven, where development as a major oil port has taken place very rapidly, it is observable that each terminal suffers a rash of incidents (most of them fortunately minor) during its first few weeks of operation, until its jetty crew gains experience.

It occasionally happens that a tanker enters her unloading port with hull damage sustained en route. If her tanks were ruptured below the waterline, oil will have escaped to be replaced by water, but as she is unloaded and her buoyancy increases, this water will flow out and will eventually be followed by the remaining oil. Kluss (1968b) describes the similar situation of a tanker stranded on a falling tide. Damage of this sort caused an overnight leakage of 250-500 tons of crude oil from the " Chryssi P. Goulandris ') into Milford Haven in January 1967 (see Nelson-Smith, 1968a, b). I n 1962 the " Benjamin Coates )' was holed in several places along the bottom of her hull when she hit rocks in the mouth of the Haven, but in this case oil escaped only immedi- ately after the impact. Sea water was pumped into the damaged tanks to raise the level of the remaining oil, which was then unloaded from above by portable pumps (Dudley, 1968).

In still waters, a leaking tanker can be surrounded by a floating spillboom, which contains the oil until it is pumped off or soaked up. Some booms are themselves made of, or stuffed with, absorptive materials such as fibrous polypropylene. Commercial booms consist basically of a floating barrier supporting a weighted skirt. Experience has shown that although they are little affected by a slight swell, choppy waves exceeding 6 inches slop oil over the barrier, while a current greater than 1+-2 knots lifts the skirt or carries oil beneath i t (Hydraulics Research Station, 1967 ; Mayo, 1968 ; Dudley, 1969). A disadvantage for more routine use in oil docks is that a continuous boom blocks the passage of traffic. Most designs are made in jointed sections which can be dismantled, while one air-filled type sinks to the bottom when deflated (Anon., 1962). I n harbour mouths (or, equally, to prevent an offshore slick from penetrating an estuary) the Hydrau- lics Research Station suggests a '' chicane )' of two curved booms, over- lapping but staggered. A more promising alternative seems to be the

226 A. NELSON-SMITH

FIG. 3. A pneumatic boom (" bubble barrier ") retaining burning oil in the harbour at Ghent (Belgium) ; note that the wind is blowing the oil towards but not across the barrier, which is partly obscured by reflected sunlight at lower right (photo: Rudolf Harmstorf Lt,d.).

" pneumatic barrier " (Stehr, 1959, 1964; Abbott, 1961 ; Sorrentino, 1963) in which a perforated pipe remains permanently on the bottom. When required, compressed air is fed into it, producing bubbles which lift a current of water to form a standing wave on the surface. This entrained water, flowing away on each side of the line of bubbles, prevents the drift of oil and other floating debris quite effectively with- out hindering the passage of shipping (Fig. 3).

I n a dock where oil is spilt regularly and can be boomed, it is usually

THE PROBLEM OF OIL POLLUTION O F THE SEA 227

feasible to provide a mechanical collector of some sort. If the area is small, a floating separator is often used, pumping its harvest ashore ; it may merely remove the surface Sayer, create a cyclone-separation vortex or concentrate the oil with rotating cylinders (the " Earle system "). I n larger docks and waterways a variety of special vessels has been used. They include barges with weir intakes and gravity separation such as " Norfolk Skimmer " (U.S. Navy Yard-see Schneider and Beduhn, 1967) or " Waferwisser " (Shell, Holland) whose outriggers hinge on each side to form a " vee-boom " collector, and those which use rotating cylinders or an endless belt to exploit the greater surface-adhesion of oil, such as " Port Service " (Baltimore -see the Batelle-Northwest Report, 1967) or " Sea Sweeper '' (BP/ Harmstorf-see Lane, 1967). Skimmers using weirs or ramps t o draw off the surface layer cannot operate in waves and are not very manceuv- rable ; those with adhesion collectors have overcome these difficulties but the oil-water mixture which they pick up will not separate properly in rough-water conditions. I n more open harbours it will therefore be impossible t o contain spilt oil or t o recover it from the water by mech- anical means. For economy of effort and materials, as well as the conservation of amenity and shore life, the oil should nevertheless be dealt with while still afloat whenever this is possible.

In estuaries there is often a problem of responsibility ; it may take months to identify and prosecute the culprit, while the body which is in the best position to deal promptly with the spill may lack the authority to allocate funds for treatment. For example, during the " Tank Duchess " incident in the Tay Estuary (February-March 1968, when about 90 tons of heavy crude oil leaked from a damaged tanker) it was found that Dundee Corporation could not finance the cleansing of waters beyond their beaches. The Harbour Trust was responsible only if the oil were a hazard t o navigation, which it was said not t o be, while the River Board had no jurisdiction over tidal waters and in any case was empowered to prosecute, but not to clean up. The result of this administrative stalemate was that after 3-4 days all the oil was stranded over many miles of shore, some of which proved extremely difficult and expensive to clean (Dundee Corporation Report, 1968 ; Greenwood and Keddie, 1968). In contrast, oil pollution incidents in Milford Haven are investigated, treated and prosecuted by one author- ity, the Harbour Conservancy Board. Because of the great tidal volume and strong currents (see Nelson-Smith, 1965) solvent-emulsifiers are routinely used, but '' Seaspray "-a specially equipped launch- applies them t o the slick as soon as a spill is reported. Only after the worst incidents or in the mostt extreme conditions does oil reach the

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shore. The cost of dispersal is borne by the offending party; the oil companies operating there have agreed to accept the harbour-master’s assignment of responsibility for this purpose, even when there is no legal proof, sharing between them the cost of treating unassignable pollution (Dudley, 1968). The general position of responsibility for pollution of the sea or shore under British law is summarized by Elliott (1969).

It is becoming an increasingly common practice to load or tranship oil at terminals or moorings which are some considerable distance off shore, where many of these remarks do not apply. Shell International pioneered the use of single-buoy moorings 10-15 miles (16-24 km) off the coast, where the cost of providing conventional shore facilities was prohibitive. The first was laid off Sarawak in 1960 and they are now in use at many terminals. Off the Libyan coast, a similar mooring system utilizes a pylon built on the sea-bed. A submarine pipeline carries oil to a manifold beneath the buoy (attached by a swivelling connection) or pylon ; valves below this connection are under remote control from the shore. The loading tanker may tie up directly to the buoy or, at a terminal in the Persian Gulf which acts as the wellhead of an offshore oilfield, to a tanker permanently moored and adapted to store the oil produced. Loading takes place through flexible floating hoses. These operations seem hazardous, but strains are less than at multi-buoy moorings or conventional jettyheads because the tanker is free to swing and thus offers the least resistance to winds and currents (Howe, 1968 ; Anon., 1969). Off-shore terminals have also been made necessary by recent great increases in tanker size ; for example, in 1968 an island jettyhead was built 10 miles (16 km) off Kuwait to accom- modate the present Gulf Oil 312 000-ton tankers of 79 ft (24.1 m) draught and projected vessels up to 450 000 tons. The only European facilities capable of receiving these tankers were opened at the same time, at Bantry Bay in south-west Ireland, solely for transhipment (see Davis, 1968). The oil is transported to refineries in Milford Haven, Europoort (Rotterdam), Denmark and Spain by tankers up to 100 000 tons.

Milford Haven can now accept tankers up to 220 000 tons and 63 f t (19.2 m) draught. Shell, lacking a refinery in the Haven, found that it was economical to use 200 000-ton tankers drawing 62 f t (18.9 m) from 1968 even though Europoort would not be deep enough for them until 1970. The fully-loaded tanker is met in the English Channel, the southern North Sea or the Irish Sea by one of two specially equipped 70 000-ton tankers which is tied up alongside t o lighten the larger vessel either at anchor or while steaming gently ahead (Fig. 4). To

THX PHOULEM OF OIL POLLC'TlON OF THE SEA 229

FIG. 4. '' Megara " (200 000 dwt) transferring 65 000 tons of crude oil to the specially equipped " Drupa " (70 000 clwt) off Lyme Bay (photo : Shell International Marine Ltd.).

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enter Europoort it is sufficient to pump off 30000 tons, which takes 10 h. Before the large tanker could dock at Thames Haven or Tran- mere (on the Mersey), she must be lightened by the full 70 000 tons in order to reduce her draught to 45 f t (13.7 m) ; this takes 16 h (Anon., 1968a). There is as yet no record of a serious spill during this procedure. Kirby (1969) discusses possible sources and Shell refer to their experi- ence of transhipnient in the Persian Gulf, pointing out that the Royal Navy refuels warships at sea as a matter of routine. Wiebe (in discussion following a paper by Edwards, 1968) advocates the off-shore unloading of tankers exceeding 100000 tons as a safety measure, to avoid the risks attending the navigation of these large vessels in constricted waterways. Nevertheless, since most spillages occur during transfer operations, the risk must necessarily be increased when multiplying the number of these operations per voyage. It has already been noted that many of the possible methods for containing and recovering oil spilt during such operations cannot be carried out under open-sea conditions.

C. Coastal industry and other sources

A coastal refinery represents the most obvious risk for oil pollution, considering the millions of gallons of crude oil and its fractions which are processed or stored there. However, refineries are planned with the possibility of spillage in mind, and, provided that the relevant codes of practice (American Petroleum Institute, 1960, 1963 ; In- stitute of Petroleum, 1965) are properly observed, serious pollution incidents occur only as a result of rare accidents. In a refinery, crude oil is purified and processed to produced a variety of fuels, lubricants and solvents as well as feedstocks for petrochemical plants. During these operations, continuous small-scale pollution occurs through leaking connections and glands, spills, breakages, sampling operations and the emptying of traps or settlement tanks. Larger volumes of oil may be released during emergency or routine shut-down of plant, cleaning and start-up operations. Water is used in some processes and inevitably becomes contaminated with the product. All drainage from the refinery site is carried to separators, usually of the API gravity type, although process-water may need special treatment first. The effluent may be held in a further settlement pond after passing through the separator.

Most coastal refineries discharge to an estuary, creek or stream rather than across the open coast, so quality standards will be demanded for the effluent by some pollution-control authority, which may place the maximum permissible oil content anywhere between 5 p.p.m. and 100

THE PROBLEM OF OIL POLLUTION OF THE SEA 23 1

p.p.m. I n Milford Haven, the limit is 50 p.p.m. and, by adopting air- cooling instead of the more normal water-cooling of plant, effluent flows are relatively small. However, there is still an appreciable effect on the vegetation and sedentary animal life of the shore in the vicinity of one refinery outfall (G. B. Crapp, personal communication, 1969). At Fawley in Southampton Water, the oil concentration in a refinery effluent is as low as 10-20p.p.m. but the rate of discharge is over 100 000 gal (455 000 litres) per minute, so a t least 1 500 gal (6 825 litres) of oil are discharged daily. The result is that in the area of saltmarsh surrounding the outfall, all vegetation is dead and even normal bacterial decomposition of the remains appears to have been arrested (Baker, 1969). As a result, erosion of the mud-flats is taking place. Petro- chemical works are often sited within or adjoining refineries and, as far as oil is concerned, the sources and control of pollution are much the same. The range of products is much wider, so the variety of com- pounds which might occur in waste waters is enormous ; their origins, removal from effluents and effects in receiving waters have been con- sidered by Huntress (1953), Montes et al. (1956) and Gloyna and Malina (1 963).

Oil wells, loading and unloading terminals, refineries and bulk users of oil are often interconnected by pipeline. Nation-wide or inter- national systems have been used in North America and the Near East for many years and are now being extended throughout Europe. In many instances they connect with marine installations or cross water- ways near the coast. The volumes and distances involved render a large pipeline an important potential source of pollution. One of the largest, the 30 inch (760 mm) Trans Arabia pipeline, carried an average of 10 million gal (nearly 50 million litres) per day in the early 1960s but is potentially capable of twice that performance. The 18 inch (460mm) pipe from Angle Bay (Milford Haven) to Swansea carries 250 000 gal (about one million litres) per hour a t an initial pressure of 800 p.s.i. (56 atmos) (OECD, 1961 ; B.P. Llandarcy, personal communi- cation, 1969). Standards for construction and operation have been laid down by the Institute of Petroleum (1964, 1967) and their significance to possible pollution is discussed by Henderson (1967). The Ohio River Valley Water Sanitation Commission (ORSANCO) guidebook (1950) and Meyer (1967) consider the causes, detection and control of pollution from pipelines. Leak-detection techniques have an accuracy of 0.03% of the flow ; in the example given by Meyer, a 30 gal (140 litre)/h leak in the 100000gal (450 000litre)/h flow of a 12 inch (300mm) pipe would be detectable by discrepancy after 24 h pumping or by pressure- drop within 2 h of shutdown. Even such a small leak should be located

232 A. NELSON-SMITH

in an underground pipe within 24 h and probably sooner in an under- water situation-although repairs in such a situation might take longer. The points where pipelines pass under waterways and shipping channels are the most liable to mechanical damage, from such natural causes as bank erosion or a shifting bed as well as from dragging anchors or dredging operations (Scherer, 1964). Such mechanical damage represents the greatest danger of a pipeline. Many thousands of gallons could be lost in a few minutes through a breakage (more than 175 000 gal-SO0 000 litres-were lost after sabotage of the Trans Arabia line in November 19691, whereas it would take 28 days for a 30 gal/h leak to lose 20 000 gal (about 100 000 litres). This sudden loss should be immediately detectable and could be minimized by stopping the pumps and isolating the damaged section. The BE' pipeline has twelve isolating valves ; its shortest section is one mile (1.6 km) long and contains about 57 000 gal (250 000 litres). When a pipeline crosses a waterway from which domestic supplies are drawn, it has been ar- ranged that the water authority has control of these valves (see Cunningham, 1954). It is also possible to place the operation under automatic control-although a serious spill in Milford Haven resulted from the failure of automatic shut-off equipment in the Waterston refinery pipeline. Pipelines are none the less much more free from accident than tankers and limitations on their wider use are largely economic.

The pollution hazards associated with bulk oil storage are con- sidered in a paper by Samson (1967) and in subsequent discussion. I n Europe, covered tanks are used, often enclosed by an earthwork (bund) sufficient to contain temporarily the entire tank contents. I n Vene- zuela, non-volatile fuel-oil has been stored successfully in open earth- banked reservoirs, the largest containing nearly 400 million gal (1 750 litres). Their cost is only 15% of conventional tanks, so it is possible that in a highly competitive industry their use may spread. The risk of pollution by seepage from a badly sited reservoir is obvious ; a less obvious danger is indicated by North American experience with smaller open sumps in which many waterfowl died, mistaking the oil surface for water (King, 1952).

The bulk distribution and storage of oil is usually controlled by skilled and responsible specialists. A much higher pollution rate, even though on a smaller scale, results from oil-transfer operations at engineering factories, garages, oil-fired heating installations, etc. by personnel who have little knowledge of the proper procedures (Hogg et al., 1947 ; McKee, 1956). I n waterside areas, surface drains empty directly to the river, harbour or sea-shore ; waste cutting, lubricating

THE PROBLEM OF OIL POLLUTION O F THE SEA 233

and sump oils are all too likely to be jettisoned down the nearest drain, together with the results of spills, leakages and overflows. All industries use petroleum oils in some form or another ; in some branches of the steel industry, in which plants are almost all sited along sea or lake shores, large quantities of oil are used in quenching baths.

I n petroleum-producing regions, but not a t present in European waters, off-shore oilfields are a significant source of pollution. Natural seepages are so well known off Southern California that a coastal feature is named Coal Oil Point and two are marked on the official Hydrographic Charts (see Merz, 1959) ; they also commonly occur in the Gulf of Mexico (Dennis, 1959), the Caribbean and the Persian Gulf. Oily material reaching beaches from this source usually has a composition which clearly distinguishes it from oil spilt during com- mercial activities (Rosen et al., 1959; Ludwig and Rich, 1964). Geo- logically, oil and natural-gas stocks are associated with salt deposits. I n many fields, particularly the older ones, large volumes of brine are produced with the oil. The Lake Barre field was recently discharging up to 320 000 gal (1 440 000 litres) per day of this (‘ bleedwater ”, containing 5-35 p.p.m. of oil, into shallow Louisiana coastal waters (Mackin and Hopkins, 1962). Oily residues were found in bottom deposits around the bleedwater outlets (about 2 p.p.m. a t Lake Barre and up to 15 p.p.m. elsewhere) but were very local, attenuating rapidly with distance.

During the process of drilling and tapping the well, carelessness, ignorance or poor communication can be as serious a cause of pollution as a t a tanker terminal. Their effects can be minimized by the obser- vation of proper precautions as laid down, for example, by the Institute of Petroleum (1964). However, towards the end of the drilling opera- tion, a sudden uncontrollable discharge may occur, resulting in a “ wild well ” (Mackin and Sparks, 1962). This is not infrequent in off-shore oilfields-Tarzwell (1967) places it a t the head of his list of serious oil- pollution sources and the Batelle-Northwest Report (1967) notes that there are about 3 000 active wells off the U.S. coast-but such events are rarely recorded in the literature. A serious (‘ blow-out ” occurred off the Texas coast in 1941, but the oil drifted to sea causing no damage (Bourne, 1968a). The leakage from the Union Oil Company well A-21 off Santa Barbara, California, received much greater publicity and its effects are still being documented. An initial blow-out a t the end of January 1969 was successfully contained by normal emergency pro- cedures, but oil and gas under pressure were then forced through a porous layer outcropping to one side of the drilling platform. After ten days, during which the magnitude of the leakage averaged 21 000

234 A. NELSON-SMITH

gal (95 000 litres) per day, this fissure was also plugged, whereupon a further leak appeared flowing at up to 4 000 gal (18 000 litres) per day. The problems of dealing with a leakage under pressure in 190 f t (57 m) of water are considerable; 100 days after the blow-out it was estimated that a total of 3: million gal (nearly 15 million litres) had been lost- over a tenth of the cargo of the '' Torrey Canyon"-within a much smaller area (Smithsonian Institution, 1969a, b ; Jones et ab., 1969; Standley et al., 1969). Oil was still flowing at the end of July 1969 and fresh leaks were reported in January 1970. I n a recent American study quoted by Batelle-Northwest (1967) i t was estimated that a minimum of 300 000 gal (1 300 000 litres) might be lost during the six weeks required to regain control of a typical GuIf Coast off-shore well. The upper limit of the estimate was, however, set a t nearly four times the volume of " Torrey Canyon's " cargo.

111. PROPERTIES OF PETROLEUM OILS A. Physico-chemical characteristics

Serious problems of pollution are caused by the crude oils, residual fuel-oils, lubricating oils and miscellaneous tank washings, sludges and tars-known collectively as " persistent oils " (Ministry of Transport, 1953) to distinguish them from light fuel oils such as gasoline (motor spirit), kerosine and gas oil which spread and evaporate very rapidly when spilt.

Crude oils are by far the most complex and variable of these per- sistent oils. A general review of their composition and properties is given by McKee (1956) and some typical values of important charac- teristics of crude oils entering European waters are listed by Berridge et al. (1968a) and Brunnock et al. (1968). When fresh, they have relative densities in the range 0.829-0-896, although evaporation of the low- boiling " light ends " quickly increases this to 0.921-0.975 for an " atmospheric residue " boiling above 370"C, or to 1.023-1.027 for a Middle East crude residue boiling above 1000°C (the density of sea water being 1.025). Smith (1968) gives a table showing the loss of bulk and gain in density of Kuwait crude oil as progressively higher-boiling fractions evaporate from it, reproduced as Table I .

The '' pour-point "-an imprecise value giving some indication of whether an oil will spread or solidify on a cold surface-varies from 7°C (Brega, Libya) to minus 34OC (Tiajuana, Venezuela). The Libyan oil has 11.4% wax against 4.8% in the Venezuelan; Middle East crudes contain 5.5-7.0y0 wax and their pour-points are also intermediate. Kinematic viscosity (measured at 38OC) is fairly uniform for these

THE PROBLEM O F OIL POLLUTION O F THE SEA 235

TABLE I

Loss of Loss of Loss of Relative density of f rac t ion wt :h voi l /o residue (at 15.5'17)

up to 100°C 9.0 1 1 . 8 0.895 up to 200°C 13.0 27.7 0.926

up t o 400°C 53.1 58.5 0.983 up to 300°C 38.1 43.6 0.955

crudes at 4.13-9.6 cRt except €or Tiajuana, which is much thicker at 25 cSt.

Fuel and lubricating oils lack volatile components and are thus not subject to loss or thickening by evaporation. Some lubricating oils are fairly thin (McKee quotes a viscosity of 250 cSt a t 20°C for an S.A.E 30 oil) whereas residual fuel-oils are essentially crude oils from which the lighter fractions have been distilled, and are thus very thick and heavy at sea temperature (see, for example, Blade, 1966). Sludges settle out from crude oils during transit and may have a wax content as high as 37% (Brunnock et al., 1968).

The solubility of hydrocarbons in water is proverbially very low, but is appreciable in straight-chain paraffins up to C, and in several of the liquid aromatics-for example, a t sea-water temperatures : benzene, 820 p.p.m. ; toluene, 470 p.p.m. ; pentane, 360 p.p.ni. ; hexane, 138 p.p.m.; heptane, 52 p.p.m. (McKee, 1956; Hodgman et al., 1960). McKay (in discussion following paper by Wardley Smith, 1968b) quoted a solubility of 1Op.p.m. for nonane, pointing out that the solubility reduces by a power of ten for every three carbon atoms added. He therefore suggested that a ton of dodecane might be dis- solved in each 100 mile2 (256 km2) of the English Channel, although the entire Channel would be required to dissolve a ton of octadecane. Freegarde (during the same discussion) reported that increases in the oil content of sea water in the Western Approaches had been detected at the time of the " Torrey Canyon " incident, using spectrofluorimetry, from a normal 3 parts to over 20 parts per 1 000 million.

The chemical composition of crude oils has a bearing on both their toxicity and the changes which they undergo when spilt a t sea. Apart from the water-soluble phenolic compounds, the most toxic elements are the more volatile aromatic hydrocarbons. During the early stages of a spill, an aromatic crude such as Kuwait (whose high sulphur con- tent of 2.5 yo tends to inhibit oxidative processes) will be more toxic than the highly paraffinic Libyan, with 0.21% sulphur. Oxidation may

233 A . NELSON-SMITH

be catalysed by sunlight or by trace metals, such as vanadium, which are present in the oil. The products may be water-soluble or surface active and may thus reduce the bulk of the slick or contribute to its emulsification. Compounds originally present in crude oil may also contribute to the formation or stability of emulsions, for example resinous “ asphaltic ” particles and sulphonic acids (Pilpel, 1954, 1968).

B. Behaviour of spilt oil on sea and shore

When a thin oil is spilt on a clean water surface it will rapidly spread until, at least under theoretically perfect conditions, it has become a monomolecular layer. Crude oils on natural waters probably never achieve this, but the typical iridescence of a small slick indicates that its thickness is 1-5-10 x mm, which represents about 150- 1 000 litres/kmz. Quantities less than this produce a silvery sheen, colours begin to appear at the lower limit and become dull a t the upper limit. A thicker slick is dark, without interference colours (Stroop, 1930; American Petroleum Institute, 1963). As the oil spreads, its more volatile constituents evaporate and the water-soluble materials are leached out. The remaining residue will have an increased viscosity and pour-point, thus a lessening tendency to spread further, so that spreading is a self-retarding phenomenon. Blokker (1964, 1966) has given equations for the spread of an oil-slick which are elaborated €or various crude oils by Berridge et al. (1968a) in an account of their field experiments.

Evaporation plays a considerable part in reducing the bulk of a crude-oil slick; i t is estimated that about one-third of the “ Torrey Canyon’s ” cargo of Kuwait crude was lost by evaporation following the spill (Brunnock et al., 1968), equivalent in effect to the removal of all fractions boiling below about 300°C (see Table I, p. 235). McKay (in discussion following Brunnock’s paper) pointed out that this quantity of hydrocarbons equals the average total amounts of sulphur dioxide and smoke in the atmosphere over Great Britain, so that the “ Torrey Canyon ” stranding contributed substantially to air as well as water pollution. Although oil traditionally calms rough waters, appreciable amounts are still carried away by wind from the tops of breakers at sea or from waves as they strike the shore (ZoBell, 1964). Considerable damage was caused to lichens and flowering plants on Cornish cliff tops by wind-blown oil-spray from below (Ranwell, 1968a, b).

Very large amounts may also disappear by the sinking of heavy residues, often aided by the incorporation of water during the formation

THE PROBLEM O F OIL POLLUTION OF THE SEA 237

of emulsions. Some 20 000 tons of crude oil were lost from the “ Anne Mildred B r ~ v i g ” but never appeared on the nearby beaches of NW Germany, it is thought because they sank at sea (Stehr, 1967). The reverse process has been recorded on at least one occasion when about 6 400 tons of heavy fuel-oil were spilt in icy seas, sinking to the bottom but reappearing later under warmer conditions (Dennis, 1959).

Crude oil emulsifies very readily a t sea, forming stable water-in-oil emulsions which can contain up to 80% water (Berridge et al., 1968b). Such emulsions are stiff, yellowish-brown in colour and, since the “ Torrey Canyon ” incident, have become widely known as “ chocolate mousse ”. The process of emulsification slows down the tendency of a slick to spread. The viscosity of “ mousse ” is in excess of 1 000 cSt (Canevari, discussion following paper by Moore, 1968) and it is more likely to break into ragged patches or “naps ”. However, by the in- corporation of so much water, the total amount of material which might eventually require removal from a beach is considerably increased.

Where there are large quantities of suspended matter, for example in tidal estuaries, this also becomes incorporated into the oil, increasing its tendency to break up and sink (Poirier and Thiel, 1941). Chipman and Galtsoff (1949), observing this, carried out an investigation on the intentional removal of oil by sinking with specially-treated sand. Hartung and Klingler (1968) report several observations on the occur- rence of sunken oil in aquatic sediments. Their experiments agree with those of Chipman and Galtsoff, that increasing salinity reduces the ease with which oil is sedimented-sinking was most effective in fresh water. Masses of sunken oil, rolled along the bottom by waves and currents, accumulatz larger particles of sand, shells and small stones ; appearing on the beach as hard tarry balls, they are described as ( ( coquina ” (Dennis, 1959; see also Stander and Venter, 1968). The formation of these discrete masses of oil probably assists in processes of biological degradation, which takes place largely at the oil-water interface (see, for example, Orton, 1925; comments by Gunkel following paper by Ramsdale and Wilkinson, 1968 ; Langston, 1969).

I n experiments on the rate of spread of small samples of crude oil on calm waters, Berridge et al. (1968a) found that 9 gal ( 2 $ litres) pro- duced a slick of 7 ft (220 cm) radius in 30-60 s, but in winds exceeding 3 mile/h (1.35 ms -l) the slicks moved bodily faster than their rate of spread. Over the long term, the pattern of oil pollution along some coastlines corresponds predictably with seasonal changes in the strength and direction of ocean currents (Dennis, 1961). Observations on the movement of individual slicks a t sea suggest that the wind has more effect than water movements although, in making predictions, due

238 A. NELSON-SMITH

allowance should be given for strong ocean or tidal currents. Calcula- tions made when plotting the drift of " Torrey Canyon " oil showed it to move in the direction of the wind at about 3.4% of its speed (Smith, 1968). This agrees well with measurements of surface drift in the Atlantic made by Hughes ( I 956), using floating plastic envelopes which travelled with the wind at 3.3% of its velocity. An oil-slick released experimentally in Japanese waters travelled at 4% wind speed (re- ported by Brockis following Berridge et al., 1968a) while the German Hydrographic Institute, plotting the movement of oil from the " Gerd Maersk " after her accident in the North Sea in 1955, showed that i t moved a t about 4.2% wind speed (Tomczak, 1964). Earlier experiments at sea off the United States in 1926-27 and off the British Isles in 1952 are referred to in the Faulkner Report (Ministry of Transport, 1953). Slicks were followed for 90 miles over 72 h during the American experi- ment, when it was concluded that most persistent oils will form an invisible film and thus " disappear " within 100 h of discharge; the British experimenters tracked a slick for 20 miles over eight days. Evidence from the Department of the Government Chemist, appended to the Report, suggests that even very thin films can build up on a windward shore to cause appreciable pollution. Berridge et nl. (1968b) report that emulsions containing less than 50% water appear, on casual inspection, to be undiluted oil. These emulsions probably form thin films and ultimately disappear, whereas " mousses " containing 5040% water remain as a film over I mm thick. The 30 000 toils of oil which were converted into " mousse " and polluted the north coast of Brittany on 1 1 April 1967 were spilt from the " Torrey Canyon " on 18-20 March and followed an irregular course eastwards for about 140 miles, touching Guernsey on 7 April before drifting south over the remaining 40 miles. A further 40 000-50 000 tons, released on 26-30 March, moved southwards from about 2 April for nearly 200 miles, passing Ushant on 1 7 April and penetrating well into the Bay of Biscay by 1-3 May. After apparently successful sinking operations, a small quantity eventually reached the south coast of Brittany on 19- 20 May (Smith, 1968).

When the slick reaches the coast, its behaviour depends on the nature both of oil and shore. In all but the heaviest pollution, much of the oil will be carried to the strandline along high-water mark by successive tides. Well-weathered or heavy oils become mixed with mineral or vegetabIe particles during this process, forming the oil-cakes mentioned above. Those which are thin, because freshly spilt or by the action of hot sun, may cause greater trouble by sinking into sand and shingle or clinging to seaweeds. The most troublesome beach to

THE PROBLEM OF OIL POLLUTION O F THE SEA 239

clean is one of large pebbles, between which oil may sink to a depth of 0.5-1 m (see Wardley Smith, 1968a). Oil does not sink so readily into wet sand, but breakers may throw fresh sand over it, burying it in layers like geological strata (Fig. 13, p. 276). I n this way a badly- polluted beach may appear clean shortly after the stranding of the oil, which is revealed later by the removal of surface layers during storms or in seasonal sand-movements (ZoBell, 1959, 1964; Smith, 1968; Kolpack, 1969).

Oil may also persist on dry rock surfaces or amongst weed, barnacles and mussels, where in addition to the biological agencies discussed below it is slowly removed by drying, hardening and the incorporation of sand particles, finally eroding or flaking off. Although they fail to wet the mucous body surfaces of animals or the mucilaginous surface of lower-shore algae, some oils cling to the byssus-threads of mussels, the horny outer layer of shells and upper-shore weeds which have a naturally oily surface. At the head of the shore, oil also has an affinity for some maritime grasses and flowering plants, which have been used in the mopping-up of localized spills.

Tide-pools become covered with a thick film of oil, but this has a surprisingly small influence on gas-exchange across the surface. Roberts (1926) showed that during a 24-h test period, water depleted of oxygen by boiling reached 99% saturation below a film of diesel oil 0.002 mm thick and 60% saturation below an 0.03 mm layer. Boswell (1950) found that a layer of crude oil 0.5 mm thick reduced the rate a t which boiled sea water absorbed oxygen to 85% of his uncovered control during a six-day test. Brown and Reid (1951), in similar experiments over a two-day period, found that in some tests a 1.4mm layer had no detectable effect; a t worst, the amount of oxygen absorbed through the oil was 75% of that taken up by the con- trol sample. Water beneath a 17 mm layer absorbed 73% as much as the control. During the pollution of the Santa Barbara Channel by a ieaking off-shore oil-well, the oxygen saturation beneath a " heavy slick " (thickness not specified) was 98.5% of that in clear water nearby. However, light intensities beneath the oil, measured on two occasions, were generally 1% of surface intensity and at best 5-10% (Smithsonian Institution, 1969b). This attenuation is likely to be unimportant be- neath a moving oil-slick at sea but may have greater effects in rock- pools which, on a sunny day, are normally supersaturated with oxygen from the photosynthetic activity of the algae growing in them. It seems probable that a layer of dark-coloured oil would also raise the water temperature by its absorption of solar energy and by blanketing the surface of the pool, but measurements or estimates of the magnitude

240 A. NELSON-SMITH

of this effect are not to be found in the literature. Spencer (1967) found that mud in an Essex estuary was warmed through 5-6°C during tidal exposure in late summer, raising the temperature of the returning sea water by about 1°C.

C. Detection and identi$cation liuman senses can detect surprisingly low concentrations of petro-

leum oils. Melpolder et al. (1953) found that a very sensitive nose can detect 0.005 p.p.m. of gasoline (motor spirit) in cold water, receiving a " strong odour " from 0-01 p.p.m. Ineson and Packham (1967) quote the even higher sensitivities of 0.00005 p.p.m. for motor spirit (with additives) and 0.0005 p.p.m. for diesel oil, although heavier fuel and crude oils are detected only at 0.2-25.0 p.p.m. Oily taint in fish and other sea-foods or in drinking water can presumably also be detected at these levels. An oil-film 4 x 10-5 mm thick (corresponding to about 0.04 ml/m2) is just visible in the most favourable of normal lighting conditions (Stroop, 1930 ; American Petroleum Institute, 1963). Dangl and Nietsch (1952) claim that 0.01 p.p.m. of mineral oil can be detected by blue fluorescence at the meniscus of a sample under ultra-violet light, although the specificity of this test has been ques- tioned (see Ineson and Packham, 1967). I n the field, oil-slicks invisible to the eye can be recorded from the air by infra-red colour photo- graphy (Cowell, 1969a). It is also possible to distinguish an oil-film from the effects of wind, fish-shoals or floating debris which sometimes resemble a slick. The necessity for processing the film involves a delay, but the technique may prove useful for the enforcement of anti- pollution legislation. A simple field-test was reported by Weir (1964), who discovered that kerosine contaminating a drinking-water supply stopped the active movement of a small piece of camphor dropped on the water surface. Camphor also moves actively on clean sea water and is completely arrested by a film of crude oil at the lower limits of visibility.

A rapid method which can determine less than 0.1 p.p.m. of petro- leum oils in water is the combustion of a small water sample in oxygen (van Hall et al., 1963). Inorganic carbon is first removed by acidifying the sample. The gases evolved are passed over heated cupric oxide and carbon dioxide is determined in the gas-stream, using an infra-red analyser. It should be remembered that the technique determines all organic carbon and is not specific to hydrocarbons. Webber and Burks (1952) stripped light hydrocarbons (C, and below) from water in a stream of carbon dioxide. Melpolder et al. (1953) were able to include all those boiling below 200°C by passing hydrogen through a water

THE PROBLEM OF OIL romwIoN OF THE SEA 14 1

sample heated to boiling. The vapour was trapped in liquid nitrogen and then dissolved in carbon tetrachloride for analysis by mass spec- trometry. Such low-boiling fractions are, however, not characteristic of oil spilt a t sea and the concentration of samples is more usually achieved by filtering the water through a column of active charcoal- see, for example, Rosen and Middleton (1955) and Greenberg et al. (1 965)-or by liquid/liquid extraction with benzene, chloroform, carbon tetrachloride or hexanes. Kirschman and Pomeroy ( 1 949) discuss the merits of various solvents and extraction methods. Most are unreliable where the original concentration lies below 10 p.p.m. Merz (1959) found chloroform to be the best solvent for extracting oily material from beach deposits. Hartung (1963) used carbon tetrachloride to extract oil from the plumage of ducks killed in a pollution incident. Standard laboratory methods for the sampling, determination, and analysis of oils in water are given by the American Petroleum Institute (1957) and the American Public Health Association ( I 960) ; techniques for the quantitative determination of mineral oil arc briefly reviewed by Blokker, discussing a paper by Ineson and Packham (1967). The main problem with such determinations is that petroleum, being a complex mixture, has no outstanding overall characteristics. Various methods may, by their nature, exclude certain components or include extraneous organic materials in the result : for many analytical pur- poses, ‘‘ oil ” and “ grease ” are terms defined on the basis of the extraction or analysis recommended (see, for example, Ludwig et al., 1965).

Gravimetric or volumetric methods involve the measurement of a solvent extract after evaporation under standard conditions. The detection limit is about 5 p.p.m. and up to 30% losses are to be ex- pected. The extract may be purified by chromatographic separation on alumina before evaporation and weighing, which increases the sensitivity to 0.1 p.p.m. and also increases the accuracy. Alternatively, the density of the extract may be obtained in a pycnometer (see, for example, Levine et al., 1953) and compared with that of the pure solvent ; the density of the oil, if unknown, has to be assumed. Using carbon tetrachloride, the method is accurate only down to 10p.p.m. but this sensitivity is increased to 0.3 p.p.m. by substituting the much denser tetrabromoethane. Optical methods may be applied to the partially evaporated extract, for example, measurements of infra-red absorption at 3.3-3.5 p are sensitive to about 0.1 p.p.m. and are fairly accurate unless there is a high proportion of low-boiling aromatics, whose i-r absorption is weak (Simard et al., 1951). Ultra-violet light at 2 700-4 000 A is strongly absorbed by petroleum oils, permitting a

242 A. NELYON-SMITIL

high sensitivity, but the absorption is due only to aromatic rings and similar structures. Thus the precise nature of the polluting oil must be known and the error can be quite large (Harva and Somersalo, 1958). Ultra-violet fluorescence is an extremely sensitive measure for oils rich in aromatics, although interference may be experienced from naturally-occurring polynuclear aromatic hydrocarbons. A detection limit of 0.001 p.p.ni. is claimed and reference has been made above to determinations of 0.003 p.p.m. in coastal Atlantic Ocean water. Oil adsorbed onto active charcoal can be extracted in acetone and suspen- ded in water with the aid of a detergent, when the turbidity of the sample is measured (Sherratt, 1956; 1962). The detection limit is about 1.0 p.p.m. ; the method will not determine water-miscible frac- tions and assumes a constant particle-size in the suspension, although it may vary from component to component.

Marine oil pollution is often heavy enough not to require confirma- tion in the laboratory ; the problem is then to determine the probable nature and source of the oil. This involves either comparisons with suspected sources, if samples can be obtained from them, or an analysis sufficiently detailed to characterize the polluting sample. A simple comparative method utilizes the patterns revealed under ultra-violet light after a crude form of paper chromatography. Schuldiner (1951) allowed spots to spread in concentric circles, whereas Herd (1953) suspended a paper strip overnight, dipping into an ether solution of the oil, to obtain bands of varying width and density. These papers can be stored for several years and have been used in successful prose- cutions. Johannesson ( 1955) made similar comparisons, using the vanadium and nickel content of ashed fuel-oils to determine the source of harbour spillages. Brunnock et al. (1968) investigated the usefulness of vanadium, nickel, sulphur, wax and asphaltene content in identifying beach pollution. They also give distillation curves and n-paraffin profiles of crude oils, their residues and beach deposits, concluding that these data make it possible to determine which crude is responsible for the pollution, a t least amongst those normally entering European waters. It is pointed out that tank sludges accumulate over a number of voyages, whilst fuel-oils are usually blended from several different crudes, so that pollution from these sources poses problems of analysis and interpretation.

Rosen and Middleton (1955) adsorbed samples of polluting oil on silica gel, eluting aliphatics with iso-octane and aromatics with benzene. The infra-red absorption spectrum given by each fraction between 5 and 1611 proved sufficiently distinctive to match samples from the known source of the oil. Their later work (Rosen et al., 1959) showed

THE PROBLEM OF OIL POLLUTION OF THE SEA 243

that such spectra were, in general, useful more for confirming the nature of the pollution than for identifying its source. Meinschein and Kenny (1957) used a similar method, eluting successively with n-hep- tane, carbon tetrachloride, benzene and methanol. They analysed the eluates by infra-red and mass spectrometry for the higher-boiling hydrocarbons occurring in soils. According to Melpolder et al. (1953), mass spectrometry permits easy calculation of hydrocarbon type- analysis from a sample containing 0.1 p.p.m. oil.

Paper chromatography is a simple, rapid method of analysis which has been applied to the identification of crude oils by Bhattacharya (1961). As a technique, it has t o some extent been replaced by separa- tion on thin layers of silica gel, alumina or porous synthetic polymers. Thin-layer chromatography has been used mostly for aromatic or heterocyclic hydrocarbons (Kucharczyk et al., 1963 ; Sawicki et al., 1964; Janak and Kubecova, 1968), but Snyder (1968) has developed a solvent suitable for the separation of saturated hydrocarbons and ole- fins. Gas-liquid chromatography is also rapid and very sensitive, but until recently it was restricted to hydrocarbons of C, or less, at best, those boiling below about 350°C (Halasz and Wegner, 1961). Ramsdale and Wilkinson (1968), using a dual-column GLC apparatus in a pro- grammed temperature-gradient, have since produced curves with peaks corresponding to paraffins of C,, or higher, boiling at about 5OOOC. The chromatogram of a fuel-oil has a general shape which distinguishes it from that of a crude. Weathered oil from beach pollution produced a curve generally resembling that from tank residues. Evidence of blending can be seen in some fuel-oil chromatograms and a peak near C,, seems typical of Kuwait crude. As well as their use in making direct comparisons of the pollution and its possible source, it seems that a reference collection of the gas-liquid chromatograms of typical oils could be slowly accumulated.

IV. EFFECTS OF OIL POLLUTION A. Mode of action and toxicity of oils

1: Birds Most marine animals are protected from oil to some extent by the

fact that it fails to wet their exposed flesh, which is usually covered by a film of mucus. The plumage of sea-birds is water-repellent but oleophilic, so they lack this basic protection. Ducks, auks (razorbills Aka torda L., puffins Pratercuka arctica L., Uria spp.-guillemots in Europe or murres in N. America), divers Gavia spp. and penguins are particularly at risk because they and the oil both normally occur on the

244 A. NELSON-SMITH

water surface; gulls (Larus spp.), gannets (Sula spp.) and their relatives are far more aerial, whereas waders feed on slioras and mudbanks. Auks and divers swim for some distance underwater and if they surface in an oil-slick their backs and wings become covered. Bourne (1 968b) observed that their immediate raaction to oil was to dive again, but in any large-scale pollution this would almost certainly rasult in further oiling. Gulls, swimming into oil on the surface, flew off. I n contrast, long-tailed duck CZanguEa hyemdis (L.) in the Baltic are reported to settle preferentially in oil patches (International Committee for Bird Preservation, 1960 ; Lemmetyinen, 1966).

The primary effect of oil on sea-birds is t o penetrate or cling t o their plumage, which mats the feather structura. I n a lightly-oiled bird, water can then fill the spaces in which air is usually trapped, eliminating heat-insulation and reducing buoyancy (Portier and Raffy, 1934 ; Thing , 1952; Hartung, 1967; Goethe, 1968). A mora heavily oiled bird is physically weighted down so that its swimrniiig movements are impeded and flight becomes impossible (Figs. 5 and 6). It has been stated repeatedly (Dennis, 1959; Tuck, 1960; Hawkes, 1961) that a spot of oil 2-3 cm in diameter on the breast of a bird is enough to bring about death, a t least in the colder seas. On the other hand, Erickson (1962) reports that up t o one-half the coastal ducks shot by hunters in the north-eastern United States showed “ oil-burn ” and many had tainted flesh, although they were otherwise healthy. Even a light oiling causes birds to come ashore if possible, whera they preen incessantly. This further damages their feather structure. They are disinclined to feed, but are certain to ingest quantities of the oil (Hawkes, 1961 ; Goethe, 1968). Hartung (1963) extracted an average of 3.6 g oil from the plumage of medium-sized scaup (Aythya sp.) found dead and ‘‘ moderately ” oiled. His experiments showed that a single dose of one-third this quantity had marked effects on mobility, al- though it was not fatal. A later sample (Hartung, 1965a) had plumage soaked with an average of 7 g oil. Ducks preen approximately half the polluting oil from their feathers within a week, most of it on the first day of oiling. The oils fed to ducks (Anas pzatyrhynchos L. and A . rubripes Brewster) by Hartung and Hunt (1 966) caused lipid pned- monia, severe intestinal irritation, fatty changes in the liver, necrosis and adrenal enlargement. Nervous abnormalities, suggesting inhibition of anti-cholinesterase activity, also reported, were probably due to organic phosphate additives in the samples of diesel and cutting oils. Amongst birds kept in optimal conditions, the amounts fed were relatively non-toxic ; all survived doses of up to 20 ml/kg body-weight of lubricating and 24 ml/kg of diesel oil. The toxicity was greatly

FIG. 5. A guillemot (Uria aalge) struggling to keep afloat after oil has destroyed the buoyancy provided by its plumage (photo : Carl Stockton).

FIG. 6. Another guillemot which died in crude oil emulsion from the ’‘ Torrey Canyon ”, washed ashore in Sennen Cove (photo : Anthony Clay).

A.I .B . -S 9

246 A. NELSON-SXITH

enhanced amongst a group kept a t low temperatures in crowded con- ditions, when an LD,, of 4 ml/kg was found for the diesel oil (i.e. about 2 ml per duck).

Hartung (1967) found that an oiled duck was under the same temperature stress a t plus 15°C as a normal duck at minus 20°C; however, even heavily oiled ducks survived at minus 26°C for as long as 36 h, provided they had sufficient fat reserves to keep up the high metabolic activity needed to maintain their body temperature. Mallard ( A . platyrhynchos) in poor condition survived this temperature for only 4 h after being covered with 7 g diesel oil. Adequate food is thus essential to survival, but in a coastal oil-spill the feeding-grounds are likely also to be affected by oil. Harrison and Buck (1967) reported that, although a high sea-bird mortality attended an overnight spill in the Medway Estuary during the autumn of 1966, the greatest effect was on the food supply. Surviving birds were forced to leave the area for the whole of the following winter.

Oil is known to affect the viability of bird eggs. Fuel-oil has been sprayed onto their eggs in successful attempts to control populations of gulls Larus spp. and cormorants Phalacrocorax carbo (L.) (Gross, 1950). In experiments by Hartung (1965b), duck eggs treated with 2- 36 mg medicinal oil (presumably non-toxic) showed a hatchability of 20y0 as against 90% in controls ; only one egg treated with more than 12 mg subsequently hatched. The undersides of ducks were then smeared with 4-5 ml of the oil before setting them to incubate fresh fertile eggs; of 19 eggs, none hatched. Rittinghaus (1956) reported an incident in which the eggs of numerous terns (Sterna sandvicensis Latham) and other shore birds failed to hatch after the parents had become contaminated with stranded oil, and Jouanin (1967) observed that gannets Sula bassana (L.) (which are normally unaffected by floating oil, since they dive only on prey that they can see) were fouling themselves and their eggs by collecting oiled seaweed as material for building nest-mounds. Hartung (1965b) further found that a single dose of lubricating oil, fed at 2g/kg, immediately halted laying and suppressed reproductive behaviour.

2. Mammals Aquatic mammals are in somewhat the same situation as diving

birds. They return to the surface at intervals to breathe and most of them have fur which readily traps oil, thereby losing its property of heat-insulation. Fewer accounts have been published, but Peller (1963) records the oiling of muskrats (Ondatra sp.), beavers (Castor Jiber L.) and even deer, while Wragg (1954) observed that fuel-oil used as a

THE PROBLEM O F OIL POLLUTION O F THE SEA 247

medium for spraying insecticide destroys the water-proofing of muskrat fur. Amongst marine mammals, damage to seals has been reported from the Antarctic by Lillie (1954), from Cornwall during the “ Torrey Canyon ” incident by Spooner (1967), and during the Santa Barbara Channel spillage in California (Smithsonian Institution, 1969b ; Cali- fornia Department of Fish and Game, 1969). The latter incident occurred during the seasonal migration of the grey whale Eschrichtius glaucus Cope, but it was observed that the whales took pains to avoid the oil. Five whales and four porpoises (Phocaena sp.) were found dead, a rather high mortality. Oil was not proved to be the cause, but the corpse of a bottle-nosed dolphin Tursiops truncatus (Montagu) had the blow-hole plugged with oil. Heavy slicks surrounded island colonies of sea-lions Zalophus californianus Lesson and sea-elephants Mirounga angustirostris Gill, amongst which further unexplained mortalities were observed. Oil damage in seals is frequently said to include severe eye irritation; a blind female now in a Cornish seal sanctuary was rescued during a fuel-oil spillage some years ago.

3. Fish

The outer surfaces of fish, their mouths and gill-chambers, are coated with a slimy oil-repellent mucus. Rushton and Jee (1923) painted the gills of trout (Xalrno trutta L.) with fuel-oil and immersed others completely in it, but commented that within a half-minute of returning them to clean water, the oil had completely floated off. They observed no harmful after-effects, but Thomas (quoted by Gutsell, 1921) found that a petroleum residue and a light fuel-oil, applied as emulsions, coated the gills of his experimental fish and rapidly killed them by suffocation. Presumably, pelagic eggs and young fish might become trapped in slicks which have begun to form a mousse ”, but evideiice from California during the wreck of the “ Tampico Maru ” (North et al., 1964) and the Santa Barbara Channel spill (Smithsonian :Cnstitution, 196913) suggests that adult fish avoid areas of heavy oil contamination. The situation in Cornwall after the wreck of the “ Torrey Canyon ” is complicated by the use of toxic emulsifiers on doatiiig oil a t sea ; 50-90% of the eggs of pilchard Sardina pilchardus (Walbaum) were dead and young fish were few or absent in plankton samples (Smith, 1968) but adult food-fish caught in the vicinity of oil- slicks and spraying operations were numerous and in good condition (Simpson, 1968a). However, Tendron (1968) reported a decrease in numbers of such fish off Ushant. He also observed oily nodules in the gut of ‘( whiting ”, probably Micromesistius poutassou (Risso), which he attributed to their feeding on oil-impregnated detritus. Tainting of

248 A. NELSON-SMITH

the flesh, resulting from contact with oil which has had little effect on the fish, is nevertheless damaging to fisheries and has been recorded on many occasions (Surber et al., 1962 ; Reichenbach-Klinke, 1962 ; Zahner, 1962; Mann, 1964; Nitta et al., 1965).

Tagatz (1961) tested the toxicity of petroleum products to juvenile shad Alosa sapidissima (Wilson). Gasoline (motor spirit) had the greatest effect while a heavy fuel-oil had the least :

TABLE I1

Median tolerance limit (p.p.m.) 24 h 48 h 96 h

Gasoline Diesel oil Bunker oil

- 91 91 204 167 - 2 417 1 9 5 2

-

Turnbull et al. (1954) found comparable values of 2 820-2 990 p.p.m. for kerosine, using sunfish Lepomis macrochirus Raf. Chipman and Galtsoff (1 949) determined the toxicity of oils adsorbed onto carbonized sand. The survival of embryos of the toadfish Opsanus tau L. ranged from one day in 100p.p.m. to ten days in 5p.p.m., using crude oil; diesel oil was less toxic and lubricating oil had no apparent effect. They refer to Veselov (1948), who found a " marked toxicity " of crude oil at 0.4 p.p.m. and of its aqueous extract at 15 p.p.m. to small carp Carassius carassius (L.). Chemical rather than mechanical effects are, of course, exerted only by water-soluble components and these are of significance to large mobile animals mainly in restricted surroundings such as tide-pools or some fresh-water habitats, where appreciable concentrations can occur. Toxicities reported in the literature are almost all for fresh-water fish. Cole (1941) considers the effects of pollutants in general, discussing variations in toxicity due to the environment or condition of the fish. Fish usually choose an optimum value for normal environmental variables, but they may be indifferent to an unfamiliar harmful substance or even attracted t o it, as Shelford (1917) found for phenol in gas-works wastes. Phenol itself may occur in oil-refinery effluents, It irritates the gills, causing heavy secretion and erosion of the mucous membrane, and also affects the central nervous and endocrine systems (Reichenbach-Klinke, 1962 ; M&licea et al., 1964). Toxicities of 17 p.p.m. for minnows Phoxinus phoxinus (L.) (Schaut, 1939) and 19 p.p.m. for sunfish (Turnbull et al., 1954) seem to be representative for most fish. Mosquito fish Gambusia afJinis

THE PROBLEM OF OIL POLLUTION OF THE SEA 249

(Baird & Girard) are particularly resistant with a median toxic limit of 72 p.p.m. (Wallen, unpublished but quoted in McKee, 1956). Naph- thenic acids occur in crude oils a t 0.05-2.5y0 generally and exception- ally a t 4.5% (MBlbcea et al., 1964). These authors reported median toxic limits of 29-36 p.p.m. for minnows and 92-118 p.p.m. for bitter- ling Rhodeus sericeus (Bloch) in 24 h and 48 h tests. Cairns and Scheier (1962) found a value of 5.6-7-2 p.p.m. over 96 h for sunfish and a U.S. Public Health Service guide (1939) reported that naphthenic acids killed minnows in 72 h at 5 p.p.m. As with phenol, the poisoning effect is irreversible. ‘‘ Naphthenic acids ” are carboxylic acids with one or more alicyclic rings.

Russian work report3d by Gutsell (1921) and Galtsoff (1936) identi- fied “ hexahydrobenzoic acid ” (cyclohexane carboxylic acid) as the toxic principle of Baku petroleum. It killed test perch (Perca sp.) and minnows at 4-16 p.p.m. The lower hydrocarbons themselves have similar high toxicities, perhaps relating to their anaesthetic properties, but their effects a t low concentrations may be reversible (Schaut, 1939). Shelford (1917) exposed sunfish for 1 h and found the following con- centrations to be lethal : ethylene, 22-25 p.p.m. ; benzene, 35-37 p.p.m. ; toluene, 61-65 p.p.m. and xylene, 47-48 p.p.m. I n experiments by Hubault (1936), 10 p.p.m. cyclohexane, 10 p.p.m. benzene or 50 p.p.m. methylcyclohexane killed roach (Rutilus sp.) in 3-4 h. Turnbull et al. (1954) also found that 20 p.p.m. benzene was the median toxic limit for sunfish in 24 h and 48 h tests, although in the tests of Toman and StGta (1959), trout (Salnzo gairdneri Richardson) survived for one day in 100 p.p.m. and almost indefinitely in 10 p.p.m. benzene. Mosquito fish were again very resistant in Wallen’s tests, with median toxicities of 386-395 p.p.m. benzene, 4 924 p.p.m. heptane and 15 500 p.p.m. cyclohexane.

4, Molluscs

I n a catastrophic coastal oil spill, molluscs-usually attached to rocks or buried in sand and, a t best, literally sluggish-may suffer heavy mortalities. Diesel oil from the “ Tampico Maru ” wreck in 1957 (North et al., 1964) killed enormous numbers of Pismo clams Tivela stultorum (Mawe) and abalones (Haliotis spp.), with long-lasting ecological consequences (see below, p. 259). I n 1963 a tank-barge was stranded on the NW coast of the United States and its cargo of various fuel-oils was pumped overboard against the protests of the state Department of Fisheries. 300 000 dead razor clams Siliqua patula (Dixon) were carefully counted during the first week of pollution but were only a small fraction of the total mortality. The commercial

250 A. NELYON-SMITH

fishery based on them closed after gathering only 9% of the normal catch (Tegelberg, 1964). Commercial shell-fisheries suffered very little during the “ Torrey Canyon ” wreck (Simpson, 1968a) largely because the oil failed to reach the major oyster-layings. Shore molluscs suffered very heavily from emulsifier spraying but survived where the oil was left untreated (Nelson-Smith, 1968b).

Most toxicity studies have been on bivalves of commercial impor- tance, particularly oysters (species of Ostrea and Crassostren). At the beginning of adult life, these become permanently fixed to the bottom and are thus subject to smothering by oil sinking en masse. Almost all bivalves are filter-feeders; droplets of oil carried in the inhalent current may collect within the mantle cavity and, if the oil is emulsified or adsorbed onto silt particles, it may also cling to the gills or pass into the gut (see Spooner, 1968a, b). Gowanloch (1835) and Galtsoff et nl. (1935) investigated oyster beds near Louisiana coastal oil wells and found no evidence that continuous slight oil pollution caused mortality. They felt that it had a definite deleterious effect, but this might have been due to the salinity of the “bleed- water ” from the wells or to a fungus disease which was not detected until 1950 (see Mackin, 1962). Hawkes (1961) reported that quahogs Mercenaria mercenaria L. seem to be “practically immune to oil pollution . . . in Narragansett Bay (Rhode Island) where the bottom is literally paved with oil ”. Oysters subjected to crude oil from a “ wild well ” actually showed a lower mortality than those in clean adjacent waters, perhaps because of its effect on their predators (Mackin and Sparks, 1962). However, Gilet (1959) observed that the previously abundant Chiton polii Marion was not t o be found on quaysides in Marseilles which had become coated with oil around the waterline (although there is evidence that chitons can graze away oil without harm-see below, p. 268). Leenhardt ( I 925) showed that O . l - l . O ~ o fuel-oil has an appreciable effect on oysters (Ostrea edulis L. and Crasso- strea angulnta Lam.) and mussels (Mytilus galloprovincialis Lam.) ; 3- 4% killed his specimens in less than a week. I n a variety of experi- ments (Galtsoff et al., 1935; Chipman and Galtsoff, 1949; Lunz, 1950) the water soluble equivalent of 5-10y0 crude oil slowed down the pump- ing rate of oysters Crassostrea virginica Gmelin, probably by anaes- thesia of the ciliated gill epithelium. Such oysters feed poorly and lose condition. Where mobile molluscs such as shore gastropods become anaesthetized, they are very vulnerable to predators-as was observed during an unusually cold winter by Moyse and Nelson-Smith (1 964)- but may be washed away to deeper water, reappearing on the shore later as shown for some gastropods in Fig. 18.

THE PROBLEM O F OIL POLLUTION OF THE SEA 251

Field experiments with an " atmospheric residue " of crude oil (approximating to a naturally weathered oil) showed reductions of 20- 40% in the population of the mobile winkles Littorina obtusata (L.) and L. saxatilis (Olivi). The shells, encrusted with heavy oil, were carried away by wave action on an exposed rocky shore. I n the laboratory, this residue is non-toxic although a 6 h exposure to fresh crude oil, followed by washing in clean water, caused mortalities of 34-44y0 in L. obfusata and L. littorea (Crapp, 1969a). Mironov (1967) found rather lower mortalities from Russian crude oils tested on the gastro- pods Bittium reticulatum (da Costa), Rissoa euxinica Mil. and Gibbula divaricafa L. ; kerosine was less toxic and a heavy fuel-oil had virtually no effect. Limpets Patella vulgata L. survived for several months in aquaria on rocks covered with weathered oil but died rapidly upon contact with fresh crude in preliminary tests by Nelson-Smith (1968a). They normally close down the shell to exclude noxious liquids, but apparently fail to recognize the danger of the unfamiliar oil. Cockles (Cardium edule L.) in aerated aquaria also quickly succumbed to 0.05% fresh Kuwait crude. Simpson (unpublished, 1961) found that cockles exposed to toluene or a commercial aromatic solvent for up to 4 h and then washed in clean water suffered 25-30y0 mortalities in the following week. The toxicity of naphthenic acids has not been reported for marine molluscs, but with a pond snail (Physa heterostropha Say), Cairns and Scheier (1962) obtained a 50% mortality in 96 h with concentrations between 6.6 and 15.6 p.p.m. A comparable effect on cockles requires over 500 p.p.m. phenol (Portmann, 1968).

Edible molluscs are frequently unsaleable because of oily taints. Quahogs from some beds off Providence, R.I., have become quite inedible (Hawkes, 1961) ; as little as 0.01 p.p.m. oil can give rise to a marked taste in Crassostrea virginica and, after heavier doses, it may persist for six months (Menzel, 1948). Mackin and Sparks (1962) observed the similar persistence of taint for two months and the Faulkner Report (Ministry of Transport, 1953) refers to Morecambe Bay mussels (Mytilus edulis L.) which retained the oily taste for several months after a spillage there.

5 . Other animals: plankton

Amongst the larger bottom-living animals, the echinoderms are notoriously sensitive to any reduction in water quality, although as the majority live slightly off shore they may escape the effects of floating oil. Oily slurries have been used to form a barrier around oyster beds to protect them from predatory molluscs and sea-stars. During the " Tampico Maru " wreck, powerful surf filled the affected bay with an

252 A. NELSON-SMITH

emulsion of diesel oil (North et al., 1964) which eliminated sea-stars of the genus Pisaster for five years and caused sufficient mortalities amongst sea-urchins (Strongylocentrotus spp.) to alter the entire ecology of the area (see below). Laboratory tests showed that an 0.1% emulsion of the oil inactivates the tube-feet of these urchins. If exposed t o the oil for more than 1 h they do not recover. Even weathered tank sludge reduced the success of artificial fertilizations of sea-urchins Echinus esculentus L. and sea-stars Asterias rubens L. in experiments by Elm- hirst (1922) and caused abnormalities in the resulting larvae. North and his co-authors noted that the sea-anemone Anthopleura xantho- grammia (Brandt) was very resistant, surviving high concentrations or direct contact with the oil in tide-pools. They recalled that it was the only animal surviving in sea-water effluent ponds of a large oil refinery farther up the coast. Similarly, the jelly-fish Aurelia aurita (L). is seasonally very abundant in Swansea docks and appears undeterred by floating slicks and oily scum. In contrast, the hybroid Tubularia crocea (Agassiz) suffered 20% mortality from 0.1% crude oil in tests by Chipman and Galtsoff (1949) and all were killed within 24 h at 5%.

Of the annelids known to tolerate polluted conditions, McCauley (1966) recorded the survival of species of the oligochaete Tubifex in oily river-bottom sludges. Reish (1964) utilized the polychaete Capitella capitata (Fabricius) as an indicator of heavy pollution from oil refineries in Los Angeles harbour and Gilet (1959) report,ed it as one of the few animals to occur in large numbers on the bottom of the heavily oil- polluted port of Marseilles. Orton (1925) observed large numbers of Ophryotrocha puerilis Claparitde and Mecznikow burrowing into and feeding around a lump of weathered oil.

Lobsters Panulirus interruptus (Randall) and shore crabs Pachy- grapsus crassipes Randall were also numerous amongst the " Tampico Maru " casualties, although in chronically oil-polluted waters, the European shore crab Carcinus maenas (L.) survives well (see, e.g., Naylor, 1965) and also has a high resistance t o phenol. Its 48 h median toxicity is 56 p.p.m. according to Portmann (1968). The American freshwater crayfish (Cambarus sp. ) is eliminated from irrigation channels by weed-killing treatments with aromatic hydrocarbons at about 300p.p.m. (Shaw and Timmons, 1949). McCauley (1966) ob- served that amphipods of the genus Gammarus disappeared from an oil-polluted river whereas copepods (Cyclops sp.) survived. Rushton and Jee (1923) also found that Gammarus pulex L. was badly affected, becoming narcotized by fresh fuel-oil but also coated and trapped in weathered residues. Orton (1925) observed that the marine copepod

THE PROBLEM O F OIL POLLUTION O F THE SEA 253

Calanus finmarchicus (Gunnerus) was undamaged by engine oil leaking from a wreck and, in aquarium tests by Nelson-Smith (1968a), brown shrimps Crangon crangon L. and prawns Leander serratus Pennant survived 0.1% fresh crude oil (the highest concentration used). For comparison Portmann (1968) determined 48 h median toxic limits of 23.5 p.p.m. phenol for Crangon crangon and 17.5 p.p.m. phenol for

FIG. 7. A lump of hardened oil which has been adopted as a float by three of the oceanic goose-barnacles Lepas fascicularis (photo : John Moyse).

pink shrimps Pandalus montaqui Leach. MBlBcea et al. (1964) found phenol toxic in 30-60 h at 10-65 p.p.m. for the freshwater cladoceran Daphnia magna Straus but did not extend their tests of naphthenic acids to this organism.

Barnacles are insensitive to weathered oil, so long as it does not entirely smother them. Amongst goose-barnacles stranded in South Wales, Lepas fascicularis Ellis & Solander has been found using a lump of hardened fuel-oil as its float (Fig. 7). Smith includes a photo-

254 A. NELSON-SMITH

graph (1968 ; pl. 19B) of acorn-barnacles Chthamalus stellatus (Poli) covered with crude oil “ mousse ” to the level of the shell-apertures, but apparently healthy, and Crapp (1 969a) has treated experimental areas of C . stellatus and Balanus balanoides (L.) with numerous monthly, 6 h, exposures to fresh and weathered crude with no evidence of damage. However, fresh crude at Santa Barbara (Abbott and Straughan, 1969) and diesel oil from the “ Tampico Maru ” (North et al., 1964) had marked effects on Chthamalus ,fissus Darwin and Balanus glandula Darwin. Chipman and Galtsoff (1949) reported slowing of the cirral beat in B. balanoides, followed by failure t o close and death in three days, from 2% crude oil. Abbott and Straughan (1969) observed that in the areas of heaviest pollution, barnacles were not breeding nor were larvae settling. In Spooner’s tests (1968a), 100 p.p.m. fresh crude killed 50% of the larvae of Elminius modestus Darwin in less than 1 h.

In the field, marine plankton seems surprisingly little affected by catastrophic pollution. During the “ Torrey Canyon ” spill, slight mortalities were observed amongst phytoplankton organisms netted and cultured, but zooplankton was as abundant and varied as usual (Smith, 1968). Preliminary reports from the Santa Barbara Channel (Smithsonian Institution, 1969b) showed plankton there, too, to be normal although detailed analyses are still in progress (see Abbott and Straughan, 1969). Belikhov (1963, quoted in the Batelle-Northwest Report, 1967) and McCauley (1966) both found many Protozoa sur- viving oil pollution in rivers, but believed that the more sensitive species had been eliminated. Minter (1965) reported that the species- diversity of freshwater plankton in a series of refinery effluent holding- ponds increased as toxicity decreased ; pollutants included phenol a t about 1 p.p.m. The diatoms Ditylum brightwelli (West) Grun.) Coscino- discus granii Gough and Chaetoceros curvisetus C1. are very sensitive to kerosine and fuel-oil, which are toxic after 24 h at 100 p.p.m. or less. Melosira moniliformis (0. Mull.) Ag. and Grammatophora marina (Lyngb.) Kutz. tolerate concentrations up to 1 % although lower levels suppress the growth of the cultures (Mironov and Lanskaja, 1967). Galtsoff et al. (1935) found that growth of cultures of Nitzschia closterium E. is also retarded, but only at concentrations of oil over 25% ; lower levels have a slight stimulating effect. Elmhirst (1922) kept cultures of marine Protozoa (Oxyrrhis marina Duj. ; species of Amoeba, Diophrys and Bodo) in contact with weathered tank sludge with no ill effects. Any experimenter who has kept suspensions of fresh oil in sea water will soon observe large numbers of ciliates feeding on or around the droplets-see, for example, Spooner (1968a, b). Marsland (1933) investigated the action of a series of paraffins on Amoeba dubia

THE PROBLEM O F OIL POLLUTION O F T H E SEA 255

(Schaeffer). Larger molecules have a greater anaesthetic effect whe inhaled by mammals, but they are less soluble in water ; C , X I 4 par- affins were narcotic, but above C,, they were iiisufficiently soluble to have an effect. Goldacre (1968) extended these experiments to include cycloparaffins and aromatic hydrocarbons, which in low concentrations have the same effects. With rising concentration, these are increased irritability followed by anaesthesia, swelling of the plasma membrane, contraction of the granular cytoplasm, bursting of the membrane and death. Even after considerable swelling of the membrane, the process is reversible; the action seems to be due to solubility of the hydro- carbons in the lipid phase of the membrane.

6. Larger plants Unlike all but the simplest animals, a considerable portion of most

marine plants can be damaged without necessarily destroying their capacity to recover. Thus the algae affected by a large oil spill are likely to show less long-term damage, even without the advantageous elimination of grazing animals which usually follows such an incident and will be discussed below. The larger brown algae are covered with a coat of mucilage which is not readily wetted by fresh oils. Topshore forms which have been emersed for long enough to dry out (for example, during neap tides) are more readily oiled, especially Pelvetia canaliculata (L.) Decne. & Thur., which occurs a t the highest intertidal levels. Emulsified oils or " mousses " will cling more readily still and may cause the overweighted plants to be torn off by waves. On Santa Cruz Island in the Santa Barbara Channel, spilt crude oil covering the surface canopy of the kelp Macrocystis pyrifera (L.) Ag. was easily washed of€ by water movement, whereas the heavily oiled smaller alga Hespero- phycus harveyanus (Decne.) Setchell & Gardner quickly disappeared from the rocks (California Department of Fish and Game, 196913, c). Macrocystis was more seriously affected in the " Tampico Maru " wreck and toxicity studies carried out with the diesel oil concerned (North et al., 1964) showed that a 0.1% emulsion almost completely inhibited photosynthesis in young blades. The effect appeared in three days, although irreversible damage is caused by exposure to the oil for 6-12 h. A 0.01% emulsion inhibited photosynthesis after a delay of seven days. Fuel-oil was even more toxic. I n another study, Clenden- ning and North (1960) showed that 10-100 p.p.m. caused 50% inactiva- tion of photosynthesis in four days, compared with 5-10 p.p.m. cresol and 10 p.p.ni. phenol. Crosby et al. (1954) investigated the growths of bacteria, fungi and lower algae in a brackish oil-refinery effluent. They found that 25-50 p.p.m. naphthenic acid, introduced in an attempt to

256 A. NELSON-SMITH

control the slime, stimulated its growth by about 15% although “ shock doses ” of 300 p.p.m. phenol killed it.

Further data on algae are anecdotal rather than quantitative. Extensive algal damage has been reported, for example, by Diaz- Piferrer (1962) after the wreck of the “ Argea Prima ”. “ Torrey Canyon ” oil appeared t o cling particularly tenaciously to the laverweed Porphyra umbilicalis (L.) Xutz. (Rhodophyceae), which subsequently became discoloured, whilst North and his colleagues noted that red algae (especially corallines in rock pools) also suffered a discharge of pigment and are thus perhaps particularly sensitive to oil. Shaw and Timmons (1949) recommended the use of aromatic hydrocarbons (their mixture contained a high proportion of xylene) to clear irrigation channels. An initial concentration of 300 p.p.m., declining to 150-250 p.p.m. downstream of the treatment point, completely eliminated sub- merged freshwater plants although it had little effect on those with aerial leaves. Currier and Peoples (1954) found that 740 p.p.m benzene killed the pondweed Anacharis (Elodea) canadensis Michx. within 1 h, although a saturated solution of the less soluble (and non-aromatic) hexane was not lethal.

Mackin (1950a-c) tested the effects of crude oil on salt-marsh plants. Saltgrass Distychlis spicata (L,), glasswort (Salicornia spp.), cordgrass (Spartina sp.) and young mangroves (Rhizophora sp.) were more sensi- tive than oysters. I n one series of experiments they were damaged by 25 ml oil per square ft of water surface (about 280 ml/m2). Some plants were rapidly killed but there was a complete repopulation later. Diaz- Piferrer (1962) also found that stranded oil killed mangrove plants. Cowell and Baker (1969) described the effects of pollution of a salt- marsh by fresh crude oil spilt in Milford Haven from the tanker, ‘‘ Chryssi P. Goulandris ”. The grasses Pestuca rubra L., Puccinellia maritima (Hds.) Parl. and Spartina townsendii H. & J. Groves recovered readily; Suaeda maritima (L.) Dun. and Salicornia spp. recovered only slowly, while Triglochin maritima L., Nalimione portujacoides (L.) Aell. and Armeria maritima (Mill.) Willd. a t its sea- ward end showed no recovery in the first year. studied salt-marshes in Cornwall affected by weathered Oil from the 6‘ Tomey Canyon ”. Experiments by Baker (1969) confirm his obser- vation that fresh oil is more toxic (i.e. the phytotoxic components are volatile) ; she found that weathered oil has a growth-stimulating effect and discusses unpublished Russian work suggesting that naPhthenic acid might act as a phytohormone. In her greenhouse experiments, a 10% solution ofnaphthenic acid applied a t about 170 ml/m2 Was toxic to P,uccinellia whereas lower concentrations had no obvious effects,

Cowell (196gb)

THE PROBLEM O F OIL POLLUTION OF THE SEA 257

either damaging or stimulating. Flowering of several species was in- hibited by oiling, probably because it kills the leaves and thus inter- feres with photoinduction. Subsequent growth stimulation probably results from this inhibition, more nutrients being available for vegeta- tive growth. Chronic pollution, for example by large volumes of effluent containing a low proportion of oil, can eliminate all salt-marsh plants, as would a single catastrophic oiling. Such damage denies their normal feeding-grounds t o birds and other animals (see Harrison and Buck, 1967) and may also seriously accelerate coastal erosion or alter the pattern of silt deposition in an estuary.

The maritime vegetation of the cliffs and strand-line, often contain- ing salt-marsh species or their relatives, is equally sensitive to heavy oil pollution, which it receives most often as droplets carried on wind- blown spray (see p. 236 above; Ranwell, 1968b). Most lichens are known to be sensitive indicators of air pollution and only a few species can survive in large towns (see, e.g., Fenton, 1964). The phytotoxic action of hydrocarbons has, however, been studied in most detail using terrestrial plants. In agriculture, they have been used both as weed- killers and as carriers for insecticides. Currier and Peoples (1954) and van Overbeek and Blondeau (1954) review previous work before re- porting their own experiments on phytotoxic oils. Minshall and Helson (1949) also discuss earlier studies. Spraying a series of pure hydro- carbons on plants showed that their toxicity increases in the order: straight-chain paraffins, olefins, cycloparaffins, aromatics. Within each series, smaller molecules are more toxic than the larger ones ; octane and decane were toxic when tested by van Overbeek and Blondeau, whereas dodecane and higher paraffins had scarcely any effect. How- ever, C,, olefins showed marked effects and C,, aromatics were quite toxic. According to Currier and Peoples, benzene is narcotic. in low concentrations, depressing some cellular functions ; in high concentra- tions, low-boiling hydrocarbons in general are cytolytic and cause an irreversible increase in permeability. As the concentration rises, the cell contents leak out, the plant wilts and finally dies. van Overbeek and Blondeau found that low-viscosity oils can penetrate stomata (which aqueous solutions cannot do) and readily spread through the intercellular spaces. They suggested that hydrocarbons become incorporated in the lipoid portion of the plasma membrane, disrupting its structure and thus rendering it permeable. Similar disturbance of the fine structure of chloroplasts would account for the recorded disturbances in photosynthesis following oil pollution and perhaps also for the discharge of pigments which has often been observed. The selective action of herbicidal oils may be due to differences of mem-

258 A. NELSON-SMITH

brane structure in some families, e.g. the Umbelliferae, which are very resistant to oils (see also Baker, 1969).

B. Eflects on marine communities A very large number of sea-birds die as a result of oil pollution;

chronic pollution probably kills each year as many as die in a single catastrophic spill. Tanis and Morzer Bruijns (1968) calculated that total annual losses due to oil in the North Sea and North Atlantic amount to 150-450 thousand birds. Amongst losses quoted for specific areas, Lemmetyinen (1966) estimated an annual 10 000-40 000 (mostly long-tailed duck) in the Baltic, 1952-62; along the Dutch coast, about 11 000 (Tanis and Morzer Bruijns, 1962) and on British coasts, some- where between 50 000 and 250 000 (Barclay-Smith, 1958, reporting the results of a nationwide survey in 1951-52). Further annual surveys, utilizing many observers, have been organized for British shores since 1966-67 (see Bourne and Devlin, 1969). Estimates can never be more than very approximate, especially where numbers collected over a mile or two of coast are multiplied by several hundreds to give a " total " for a lengthy seaboard (see Tuck, 1959; Gillespie, 1968; Cowell, 1968). Furthermore, it is clear that the corpses stranded on shore represent a fraction of the total mortality a t sea, variously assumed to lie between 5% and 15%; it factor of 10 is probably the most reliable estimate (Tanis and Morzer Bruijns, 1968; Clark, 1968). As examples of mor- tality following a major tanker spill, the wreck of the " Frank H. Buck " in San Francisco Bay in 1937 killed 10 000 or more birds, of which 6 600 were guillemots (Aldrich, 1938; Moffitt and Orr, 1938); the collision of the " Fort Mercer " and " Pendleton " off Chatham, Mass., in 1952 reduced the wintering population of eiders from 500 000 to 150 000 (Burnett and Snyder, 1954) and the stranding of the " Gerd Maersk " in the Elbe estuary in 1955 affected 250 000-500 000 birds, mainly common scoter (Goethe, 1968).

From a humanitarian point of view, each of these mortalities is very regrettable; from that of a zoologist, the significance of the figures depends entirely on the bird species concerned. The gulls (Larus spp.), cormorants (Phalacrocorax spp. ), gannets (Sula bassana) and petrels (fulmars Pulmarus glacialis (L.) ; Manx shearwaters Pufinus puf inus (Briinnich) ; storm-petrels Hydrobates pelagicus (L.) and others, although often oiled, are increasing in numbers. Divers (Gavia spp.) form only a small percentage in lists of oiled birds, but the total world population is small and their reproductive rate is low, so any additional losses may be serious. Populations of sea ducks are already showing a downward trend ; the Baltic is the major wintering-ground for the long-

THE PROBLEM OF OIL POLLUTION OF THE SEA 259

tailed duck Clangula hyemalis of NW Europe, but as early as 1960 the number of migrants there was only one-tenth that recorded in 1937- 40 (Bergman, 1961). Eider Somateria mollissima (L.) and shelduck Tadorna tadorna (L.) also congregate over-winter or for moulting in areas subject to pollution incidents (see Bourne, 1968a; Clark, 1968). The auks are, however, probably the most seriously affected. They are long-lived with few natural predators, and have an extremely low reproductive rate. Guillemots, Uria aalge (Pont.), do not breed until they are three years old and then produce one brood per year, usually of only one egg. According to Tuck (1960) and Southern et al. (1965), in several species of this genus only 20% of the eggs laid produce chicks which safely reach the sea and many of these drown or are taken by gulls in their first days on the water. Clark (1968) estimates that if an oil spill halved a guillemot colony, it would take more than half a century for it to recover. Most auk colonies on each side of the North Atlantic are situated in regions particularly subject to oil pollution. Puffins, Fratercula arctica, which numbered 100 000 on Annet (Isles of Scilly) in 1907 have been reduced to 100 in 1967 (Parslow, 1967a, b) and similar declines have been recorded at other colonies. The process is an accelerating one, since smaller colonies have proportionally less reproductive success and suffer greater losses of eggs and young (Clark, 1968).

It is a commonplace that areas subjected t o chronic pollution, whether industrial, domestic or natural (e.g. of sea water by fresh water and silt from a river), usually support a less diverse population than similar unpolluted sites, although the numbers of the few resistant species may be very large. I n this respect, oil is little different from other pollutants (see, for example, Gilet, 1959; Reish, 1964). A cata- strophic pollution incident results in a similar selection of resistant species, but the system has no time in which to reach a new balance. The " Tampico Maru" wreck (North et al., 1964) provides a good example of the ecological effects of a serious oil spill. One of the main factors restricting the spread of the giant kelp Macrocystis pyrifera is the grazing of young plants by species of sea-urchins Strongylocentrotus and of abalones Haliotis. Although the kelp itself suffered immediate damage from the diesel oil spilt from the wreck and emulsified by wave-action, juvenile plants began to appear within 2-3 months. North and his colleagues suggested that their settlement was assisted by severe reductions in the population of filter-feeding mussels and scallops, which did not therefore take their customary toll of the swimming kelp spores ; but the major biological factor which made possible the great development of the kelp canopy over the next five

O C T 1959

OIb'f

JUL 1958

7w7 FIG. 8. Variations in the canopy of the giant kelp Macrocystis pyyifera (solid black) in a cove in Lower California after heavy diesel

oil pollution following the wreck of the small tanker " Tampico Maru " in March 1957. The position of the wreck, until she broke up in the winter of 1957, is also shown; redrawn from North ct al., 1964.

THE PROBLEM OF OIL POLLUTION O F THE SEA 261

years (Fig. 8) was undoubtedly the virtual elimination of the grazing sea-urchins and abalones. The wrecked tanker did, indeed, provide a breakwater to protect the initial growth of the young plants, but it broke up and was dispersed during the first winter, after which the Macrocystis climax passed through a t least two growth cycles.

No similar catastrophe on the shores of north-west Europe has yet created such an effect on the North Atlantic equivalents of this kelp, but observations have been made on the ecological effects of the " Torrey Canyon " wreck and of several spills in Milford Haven upon the intertidal zone (Bellamy et al., 1967; Nelson-Smith, 1968a, b ; Smith, 1968; Crapp, 1969a, b). These effects cannot be ascribed to oil alone, as in every case solvent-emulsifiers used to clean the shores probably caused more damage than the oil (although their most toxic components are themselves aromatic hydrocarbons-see below, p. 284). On these shores the most obvious seaweeds are three species of FUCUS, Ascophyllum nodosum (L.) le Jol. and Pelvetia canaliculata ; in large pools and at the lowest tidal levels, other brown algae such as Halidrys siliquosa (L.) Lyngb., Himanthalia elongata (L.) S . F. Gray, Laminaria spp., Xaccorhiza polyschides (Lightf.) Batt. or Alaria esculenta (L.) Grev. may make a significant contribution. Beneath these there is a '' turf '' of many species of smaller brown, red and occasionally green algae. The main grazers on the algae are the limpets Patella vulgata and the less widespread P. depressa (Pennant) or P. aspera (Lam.) (distantly related to Haliotis spp., the abalones and ormers), winkles of the genus Littorina and topshells (Gibbula spp. and Monodonta lineata (da Costa)). Factors influencing the balance between the seaweeds, their grazers and such competitors for space as the acorn-barnacles and mussels are considered by Southward (1956) and Lewis (1964). On the most heavily polluted and vigorously cleaned shores in Cornwall, which are also exposed to strong wave-action, all the limpets were killed; within two or three months they became clothed with the green algae Enteromorpha intestinalis (L.) Link., E . compressa (L.) Grev., Ulva lactuca L. and Colpomenia peregrina Sauv., which are normally confined to sheltered shores and estuaries. During the following year, a vigorous new growth of fucoids appeared to replace the " green phase ". Young limpets also began to reappear within a year of the incident, but these graze sporelings rather than mature plants. A small cove in Pembrokeshire which showed the same succession of events after a pollution incident in 1962 still had an unusually dense cover of seaweeds three years later. During experiments in the Isle of Man in which limpets were systemati- cally removed, a strip of shore also passed through a " green phase " and produced a dense growth of fucoid algae which persisted for about

262 A. NELSON-SMITH

four years. Peculiarities developed in the zonation of Fucus species and in the form of some plants of 3’. vesiculosus L. (Lodge, 1948 ; South- ward, 1956). In Cornwall it was observed that on an exposed shore where F . vesiculosus was previously represented only by its bladderless form linearis Powell (evesiculosus Cotton), the increased weed cover permitted the development of scattered plants of the more usual F . vesiculosus vesiculosus. Such dense algal growth occupies space other- wise available for barnacle settlement, and moving fronds of the weed brush away prospecting larvae. Settlement of Balanus balanoides, a northern form already at a competitive disadvantzge with Chtham,alus stellatus in south-west Britain, might well be discouraged by a pollution incident occurring at the time its larvae would be seeking settlement sites. Most available rock surfaces inspected after the wreck of the “ Torrey Canyon ” were occupied only by spat of Chtham,alus, which breeds later in the year. Similar zoogeographical differences affect the survival of the topshell Monodonta lineata which is near its northern limit in Milford Haven and was thus badly affected by the cold winter of 1962-63 (Moyse and Nelson-Smith, 1964). I ts recovery was checked early in 1967 and again late in 1968 by serious pollution incidents (Fig. 18, p. 286), although farther south in Cornwall it appears to be more resistant to oil and emulsifiers than the winkles (Spooner, 1967 ; Smith, 1968).

C. Carcinogenesis

Russian work quoted in the Batelle-Northwest report ( 1967) associated papillomatous tumours in Baltic eels with deposits containing fuel-oil, and Russell and Kotin (1956) reported carcinomas and papil- lomas on the lips of bottom-feeding fish caught near an oil refinery. However, no direct evidence is to be found in the literature that spilt oil can produce malignant growths either in marine animals or those who feed on them, although Goldacre (1968) points out that changes in the cell-membrane brought about by hydrocarbons could lead to a breakdown in cell-to-cell communication and thus to cancer. Carcino- genesis associated with oily industrial effluents or motor exhausts is usually due to benz(a)pyrene (3, 4-benzpyrene) and related polycyclic hydrocarbons. These have been detected in marine sediments off the coast of north-west France at concentrations up to 1.76 p.p.m. by Perdriau (1964) and Mallet and Priou (1967), and in the Mediterranean up to an exceptional value of over 3 p.p.m. (Bourcart and Mallet, 1965). The maximum concentration found in edible molluscs by Mallet and Priou was one hundred times less than this, although they found 0.16 p.p.m. in the viscera of a food-fish. Shimkin et al. (1951) detected 0.05-

THE PROBLEM O F OIL POLLUTION O F THE SEA 263

0.20 p p m . benz(a)pyrene in barnacles on the coast of California ; an extract injected into mice produced subcutaneous sarcomas. Plankton contained up to 0.40 p.p.m. off French coasts but only 0.006 p.p.m. off Greenland (Mallet and Sardou, 1964), suggesting that benz(a)pyrene is created during industrial activities, and it is known that to obtain it experimentally from naturally-occurring hydrocarbons they must be heated to over 400°C. However, Shabad (1967) reported Russian work on the accumulation of polycyclic carcinogens by micro-organisms and Mallet et al. ( 1 967) have demonstrated that they can be synthesized by marine bacteria from the lipids of plankton. Thus, although the major source of carcinogenic hydrocarbons in the marine environment is the relatively small amount of heated waste oils reaching the sea from industry and shipping, it is a t least possible that marine micro-organisms could manufacture them from the crude or other oils which are or&- sionally spilt in much larger quantities.

D. Rehabilitation of oiled birds

Most people show an understandable desire to help birds which come ashore oiled, although from a coldly scientific point of view this assistance is not necessary to maintain the numbers of such species as the herring gull Larus argentatus Pont. or greater black-backed gull L. marinus L. On the other hand (as shown above) a vigorous conservation policy which includes the rehabilitation of oiled specimens will soon become the only way to protect many auks, a t least of the North Atlantic region, from complete extinction. Existing methods of rehabili- tation have little success. Of 5 71 1 oiled birds (mostly guillemots Uria aalge) collected during the “ Torrey Canyon ” incident, about 150 were returned to the sea and 25-30% of these are known to have died within a month of release (Conder, in discussion following Clark’s 1968 paper ; Clark, 1969). This suggests that a great deal of trouble and resources were, in effect, being devoted to prolonging the suffering of over nine- tenths of the stranded birds. Most ornithologists advise that quick humane killing is at present the best treatment.

Beer (1968a, b) gave an account of the methods used on oiled auks after the “ Torrey Canyon ” wreck; Clark (1968) and Clark and Kennedy (1968) reviewed the wider problems of rehabilitation and conservation. Because these birds rarely come ashore until very badly affected, stranded auks will be starving, chilled, exhausted and with secondary complications in addition to oiling even before they can be collected. They must be prevented from preening or overcrowding each other and kept as warm and clean as possible before treatment.

264 A. NELSON-SMITH

Most cleansing processes remove natural as well as polluting oils and do further damage to the plumage, so the birds have to be kept a t least until they are again naturally oily and usually until they have moulted (a new but relatively untried treatment coats the plumage with wax as it removes the contaminating oil). Auks are very difficult to keep in captivity even when healthy. They eat only fresh fish (preferably taking i t from the water themselves), require sea water and are very subject to fungal infections or other diseases and deficiencies. When the survivors are finally released they are often too tame to resume inde- pendent life. It seems possible that they never resume breeding, so they do not contribute to the recovery of the colony. Nevertheless, breeding (as yet unsuccessful) has been reported in a pair of captive guillemots (Marsault, 1969) and it seems possible that jackass penguins Spheniscus demersus (Linn.) can be rehabilitated successfully in South Africa (Westphal, 1969). Bourne (196th) and Clark (1968, 1969) suggest that more research ought to be devoted to the improvement of failing auk colonies, for example by providing artificial ledges from which eggs would not be lost, or to methods of scaring birds from known slicks. Some form of acoustic buoy, drifting with the slick, would also assist in tracking the oil or relocating it if lost.

E. Public amenity and the tourist industry

Sea shores and coastal waters are used by commercial or amateur fishermen and sailors as well as other sportsmen, naturalists, and holidaymakers in general. I n harbours and enclosed waters, fresh oil is a direct danger when it constitutes a fire risk. It is also a hazard to coastal power stations, which usually draw sea water for cooling from docks or estuaries. Oil in the water may cause an explosion in the condensers and after a serious spill they have to be shut down (as a t Hayle, Cornwall, in 1967). It is now generally accepted that floating oil has little direct effect on commercial fisheries (see, for example, Simpson, 1968), although sunken oil may smother or taint shellfish and foul nets or other gear. Indirect effects on the planktonic young stages and on organisms providing food or shelter can be guessed at from the data assembled above. Korringa (1968) has called attention to an additional indirect effect. After the much-publicized " Torrey Canyon " spill, fish sales in Paris dropped dramatically regardless of the origin of the fish. Amateur fishermen are more likely to experience direct effects, as they operate close in shore if not from the beach itself, seeking coastal fish with bait taken from the shore.

Marine pursuits of all kinds have become increasingly popular and

THE PROBLEM OF OIL POLLUTION O F THE SEA 265

costly along the coasts of industrially affluent nations. The paint- work of a speedboat or sails of a yacht are easily spoiled by oil ; the oil is equally easily transferred to boat-trailers, towing vehicles, caravans and clothing. I n Milford Haven and elsewhere, yachtsmen in need of a repaint have been observed to sail deliberately into a slick of known origin, when they could be certain of compensation, but these are few compared with the numbers who are forced to spend time and money on cleaning and touching-up operations. Underwater swimming, surfing and water-skiing are further sports of increasing popularity which require expensive equipment-for example, neoprene-foam " wet suits " which can be ruined by contact with oil.

On almost any shore in western Europe, stranded oil is to be found in rock crevices, in lumps along high-water mark or in patches beneath the sand. Even if the swimmer, sunbather or walker avoids all obvious traces of its presence, the warmth of his body as he sits on an apparently clean area is likely to melt a hardened deposit, causing it to smear his skin or stain his clothes. Many resorts in the south of England now operate " detergent stations ') in addition to first-aid huts and life- guards, where the worst of the oil may be removed. Nevertheless, oil is carried or trodden into hotels, boarding-houses, caravans, cafhs and places of entertainment, ruining their carpets and upholstery. The total cost of cleaning, repainting or repair to the individuals affected, to- gether with the cost to the public of beach cleaning and other services, cannot be determined but must be large. The loss of seasonal income from holidaymakers is potentially even greater. Many countries today depend heavily on tourism (see Ricci, 1968) and it is economically the fourth most important of British industries, earning as much as the total of machinery exports. Cornwall alone has more than two million visitors per year, spending between them nearly E40 million (Croft, 1959, and in discussion after Ricci's paper ; Cowa.n, 1968). The adverse effect of a widely publicized disaster like the " Torrey Canyon )' wreck can be countered by reassurances from government ministers and agencies (which were not entirely founded on fact). After a slow start, the Cornish holiday season in 1967 was a profitable one (Grieve, in discussion after Ricci, 1968). Holiday areas can, however, acquire a reputation for chronic pollution which increasingly keeps visitors away, though they usually prefer not to admit to such a reputation, even in the form of a denial. In any final analysis, to these economic considera- tions must be added the sheer unpleasantness and frustration of finding the enjoyment of carefully chosen surroundings in hard-won leisure time marred by defiling and unnecessary jetsam of the industrial society from which most users of the sea-shore are seeking temporary escape.

266 A. NELSON-SMITH

V. REMOVAL OF SPILT OIL A. Bacterial degradation and other biological processes

Orton recognized in 1925 that bacteria play an important part in removing oil from the sea. Although Adam (1936) later ignored bio- degradation in his otherwise full discussion of the dispersal of oil a t sea, Pilpel (1968) concluded from the work of Dzyuban ( I 958) and others that bacterial oxidation could proceed as much as ten times as fast as auto-oxidation. There is no doubt that bacteria can utilize a variety of hydrocarbons under field conditions. Their activities in industrial cutting and fuel-oils are frequently troublesome (see Birkholz et al., 1961-62). Ludzack et al. (1957) observed that the amount of oil in a stretch of river receiving a refinery effluent diminished by 40-80y0 below the discharge point, according to the season, and in laboratory experiments a t summer temperatures 50-80y0 of the oil in their water samples underwent biological degradation within a week. ZoBell and Prokop (1966) found that, although oil was continually polluting bays and creeks on the Louisiana coast, its concentration in bottom deposits was generally low (see above), reaching 1% only in localized areas of recent pollution and persisting there only for a few weeks. Oil-oxidizing bacteria were detected in 94% of their mud samples.

Prokop (1 950) concluded that the presence of acclimated cultures was essential to the degradation of crude oil and McKee (1956) gave values for the biochemical oxygen demand of various organic com- pounds in cultures seeded with sewage organisms in which pure hydro- carbons gave low figures (no BOD from toluene, xylene or benzene over five days ; 1-20 g BOD/g benzene over ten days ; 0.53 g from kerosine and 0.078 g from gasoline over five days), although those containing oxygen or nitrogen had much higher demands. ZoBell ( 1 964) obtained higher figures (1.4-4.0 mg oxygen/mg sample) using mixed cultures of hydrocarbon oxidizers. I n a 35-day test a t 25"C, the samples were 47- 85% oxidized. Comparable BOD values for other substances are 1.07 (glucose), 1.18 (starch, cellulose), 1.5-1.8 (protein), 2.5-2.9 (vegetable and animal oils). However, Stone et ab. (1942) used ordinary soil " seeds " on a selection of light oils, crudes and residues to obtain after a few days cultures capable of attacking all the samples they tested. The American Petroleum Institute's manual on biological treatment for oil refinery wastes (McKinney, 1963) says, of recommended sources, " The engineer need only look under his feet to find suitable organisms." ZoBell (1946) and Voroshilova and Dianova (1950) have shown that over 100 organisms can decompose pure hydrocarbons. Pseudomonas is thc outstanding type for crudes and is represented by several marine

THE PROBLEM O F OIL POLLUTION O F THE SEA 267

species (Stone et al., 1942 ; ZoBell, 1964). There is thus little necessity to " seed " a coastal spill with cultures of specially selected organisms, nor is there any case for supposing that marine bacteria will show a lack of enthusiasm for polluting oil, as available carbon is scarce in the sea (usually less than 2 mg per litre-see Berridge et al., 1968a, and subsequent comments by Gunkel). Experiments by Gunkel (1967) showed that, under suitable conditions, normal marine bacteria decom- posed nearly 60% of added fuel-oil in 8 weeks. Light oils are oxidized more rapidly than heavier ones and paraffinic (aliphatic) hydrocarbons more rapidly than aromatics, according to Stone and his colleagues. However, Ludzack and Ettinger (1959) observed that aromatic hydro- carbons disappear from polluted streams more rapidly than aliphatics. This conflict is considered in a review by ZoBell (1950) as being due mainly to differences in the environment and the types of micro- organisms originally present there.

Gunkel (1968 and in Smith, 1968) sampled oiled beaches in Corn- wall after the " Torrey Canyon " disaster and found very high numbers of oil decomposers, especially in well-aerated situations. The greatest density (over 400 million organisms per ml of wet sediment) was higher than any he had recorded in previous oil spills and approached the maximum which could be obtained with pure cultures on artificial media in the laboratory. The average numbers of oil decomposers a t his Cornish stations varied from one-half to three times the total num- bers of other aerobes. Even where there was no oil, he obtained 50 000 oil decomposers per ml. Earlier, ZoBell (1964) had calculated that after two days' presence of oil in sea water, the population of bacteria capable of degrading i t might reach 8 million per ml. This population would oxidize about 1 mg oil per litre per day at 25"C, 0.3 mg at 15OC and less than 0.1 mg at 5 O C . Nitrogen and phosphorus might be limiting in the water but would probably be adequate in shore sedi- ments. Oxygen is also potentially limiting, but degradation takes place only at the surface of the oil. The formation of " mousse "-like emul- sions may aid the process by increasing the oil-water interface (see Berridge et al., 1968b and subsequent discussion, also Gunkel discussing Ramsdale and Wilkinson, 1968). Smith (1968) reported the occurrence of grey sulphide layers, unusual in Cornish sands, after the " Torrey Canyon " spill, taking them to be evidence of considerable decompo- sition of the oil (as might be expected by scaling ZoBell's figures up to Gunkel's population counts). Anaerobic degradation was occurring at a much slower rate; this process also depends on the availability of nitrates, phosphates or sulphates which here provide a source of oxygen. For example, complete oxidation of 1 mg of a typical mineral oil

268 A. NELSON-SMITH

under anaerobic conditions requires about 4 mg nitrate ; sea water may contain as little as 0.1 mg per litre and rarely has more than 2 mg (Pilpel, 1968). Izyurova (1952) has achieved four- to ten-fold increases in the rate of anaerobic degradation by the addition of nitrate. Crosby et al. (1954) reported the periodical abundance of sulphur bacteria in a refinery effluent holding-pond and ZoBell and Prokop (1966) con- cluded that bacteria of the genus Desulfovibrio or Desu&muculum can definitely degrade mineral oil under anaerobic conditions. Davies and Hughes (1968) disagree, but only over the precise definition of anaerobiosis. These authors reviewed the basic pathways of crude oil degradation. Treccani (1965) gives a concise account of the bacterial metabolism of individual pure hydrocarbons, on which there is a large and specialized literature. The final products of aerobic oxidation are carbon dioxide and water. Many of the intermediate products are water-soluble and almost all are readily susceptible to further attack by micro-organisms commonly present in coastal waters (Brown et al., 1951).

Intermediate products of degradation, as well as the bacteria them- selves, provide support for many higher micro-organisms. Protozoa, fungi and lower algae contribute to the slime in a brackish refinery effluent described by Crosby et al. (1954). Spooner (1968a, b) reported many ciliates amongst oil droplets, some with oil in food-vacuoles, and Voroshilova and Dianova (1950) refer to an increase in the numbers of protozoans following that of oil-degrading bacteria in polluted waters. Orton (1925) observed numbers of the small polychaete Ophryotrochu burrowing into weathered oil, he assumed to feed on bacteria. Larger animals can contribute directly to the removal of oil, although probably not actually digesting it. George (1961) reported that limpets Putella. were capable of scraping weathered oil from the rocks in the normal process of browsing. Oil appeared in the faeces, mixed with rock frag- ments and plant debris, while the limpets apparently remained un- harmed. Some months after a fairly severe spill, he found the shore cleared of oil except for a band deposited above the highest level which limpets could reach. On the worst-affected shores in Cornwall after the " Torrey Canyon " wreck, all limpets were killed by emulsifier spraying (see below), but it was seen that Patella and the topshell Xonodonta had been grazing oil from the few unsprayed reefs (Holme, 1967 ; Spooner, 1967; Smith, 1968) and in Brittany (Fig. 9). Spooner and Spooner (1968) observed that chitons-which occupy a similar ecological niche to limpets but are there nearly twice as large-removed from coral rock in the Bahamas much of the fuel-oil spilt from the stranded " General Colocotronis " (Figs. 10, 11).

THE PROBLEM OF OIL POLLUTION OF THE SEB 209

Aljakrinskaya (1966) showed that the filtering activities of mussels Mytilus from the Black Sea were not slowed by crude oil in suspensions up to 1%. The oil was accumulated in mucous strings and discharged as pseudofaeces. Spooner (1968a, b) found that 0.4% suspensions of

FIG. 9. Tracks made by the radula of & limpet (Patella vuZga,ta) in grazing oil from rocks at St. Jean du Doigt (FinistBre) ; an idea of scale is given by the acorn-barnacles at the edge (photo : N. A. Holme).

weathered Kuwait crude and of bunker C oil wer2 filtemd by mussels, which rejected some of the oil as pseudofaeces but ingested a propor- tion. The oil tended to " pond " in the gut but was eventually expelled in true faeces. It seems unlikely that such globules could be digested by the mollusc, but the incorporation of oil into faeces apparently made it more readily available to micro-organisms.

Fro. 10. A chiton (A4canthopleura yranulafa Gmelin) in the area of coral rock which it has rleared of oil, following the stranding of tho " General Colocot,ronis " off Eleu- thera (Bahamas). The anim.al is abont 2 inches (5 rm) long (photo : C. M. Spooner).

FIG. 11. The chiton, removed to a dish. with faeces (right) which clparly contain 011 (photo : Marine Riological Association. Plymouth).

TIIE PROBLEM OH’ OIL POLLUTION OF THE SEA 27 1

B. Dispersal, sinking and recovery at sea

It is always preferable to deal with spilt oil on the water, before it reaches the shore. I n reasonable weather conditions it is usually easy to transport and apply dispersing or sinking agents by ship. When these are toxic, their rapid dilution and the relative scarcity of plants and animals in the open sea makes for far less biological damage than their application directly onto the densely-populated intertidal zone.

I n treating oil spillages in European waters, the method most used so far has been to spray with solvent-emulsifiers. The more effective of these, such as B P 1002, Gamlen, Fina-Unisol or Essolvene, contain 8-30% non-ionic surfactant and 60-80% hydrocarbon solvent (usually of high aromatic content) with additional emulsifiers and stabilizers (some formulations are given by Smith, 1968). They are designed to be laid on the oil in a fine but powerful spray without dilution. Under laboratory conditions as little as 10% of the oil volume produces a stable milky emulsion after shaking, although in the field any quantity from 25% to twice the oil volume may be needed. The mixture must tht JI be agitated vigorously to disperse it as an oil-in-water emulsion. This can be accomplished by making a faster return journey through the slick (or using a following vessel) to break it up by propeller action, or with high-pressure water hoses. Some surfactant mixtures are effec- tive without the addition of hydrocarbon solvents and can be applied in polar liquids (water or alcohols). Examples of these are the American Corexit (see Moore, 1968) and Polycomplex-A (Spooner, 196th) or the British Dispersol 0s. Crop-spraying aircraft might appear to be suit- able for applying dispersants, but the payload is very small if they have to fly over any distance (Wardley Smith, 1968b). A Canadian aircraft used for fighting forest fires carries a payload of ten tons of water and could be modified to deliver dispersants. The mixture could not be agitated from fixed-wing aircraft, although Moore suggested that the rotor-wash from a helicopter might be adequate.

Oil can be sunk by the addition of any fine, dense material-for example, dry sand-as often happens naturally ; unfortunately, it then coagulates on the bottom into large globules which rise at the slightest disturbance. Because of this, and due to fears that sunken oil might smother shellfish beds, interfere with fish feeding or breeding grounds and foul nets or pots, British official policy seemed until very recently to be opposed to sinking oil. I n America, Carbosand (sand coated with heavy oil and then heated sufficiently to char the coating- see Hofmann, 1949) has been in use for some years, but it is not an effective oil-binder (Schneider and Beduhn, 1967) and is rather toxic

272 A. NELSON-SMITH

(Chipman and Galtsoff, 1949). During the “ Torrey Canyon ” affair the French used “ craie de Champagne ”, which is ground calcium carbonate treated with about 1 yo sodium stearate, apparently with some success (Bone and Holme, 1968 ; Smith, 1968). Stearated whiting has been advocated in Britain. Various absorbent waste materials such as crushed cinders, brick-dust or pulverized fuel-ash can be rendered hydrophobic but oleophilic by treatment with chloro-silane vapour a t about 0.2% by weight (Anon., 1967a; Wardley Smith, 196813, c). Wardley Smith also refers to a gypsum residue called “ Stucco ” which is a by-product of the manufacture of phosphoric acid. It sets hard in sea water and should thus bind the oil in a firm mass on the bottom.

Early attempts a t applying these materials were made by spreading the dry powder over the oil slick in about a 1 :1 ratio. After a pause, the mixture was sunk by agitation with propellers or water-jets. This is successful in harbours, for which most products were originally in- tended. The French, operating in Channel and Biscay waters, had to withdraw naval vessels because chalk-dust carried by the wind was ruining military equipment (Wyllie and Taylor, 1967). It has been proposed more recently that hydrophobic sinking agents could be applied as a slurry in water (see, for example, Holdsworth, 1968). Another technical objection is that the nearest port a t which a sufficient quantity of the material could be loaded might be quite distant from the slick. Stocks of the agent of choice might similarly be stored at a distance from that port. The costs of transport, as well as of raw materials and storage, could be minimized by a further suggestion from Holdsworth that provision should be made for fitting suction-dredgers with spray-booms. I n dealing with an off-shore spill, such a dredger could be loaded with sand from the nearest shoal and her cargo could be treated with a water-repellent agent while still wet in the hoppers and then distributed through the spray-booms as a slurry while she steamed through the floating oil.

Oil adsorbed onto inert particles is in a state favourable to bacterial degradation and a sinking agent could even be seeded with the nutrients likely to be limiting on the sea-bottom, or with oil-degrading bacteria themselves (Anon., 1967a; Davies and Hughes, 1968). The fine drop- lets produced by dispersants may also be favourable to biodegradation, but many emulsifiers are toxic to oil-degrading organisms as well as to plankton in general. As neither sinking nor dispersing actually destroys oil, methods which permit its collection and disposal seem attractive. Natural materials such as straw (McKay, 1967 ; Roberts, 1967), pine-bark (Anon., 196810) or maritime vegetation (gorse and dune grasses) have been used in emergencies by drawing them across the

THE PROBLEM OF OIL POLLUTION OF THE SEA 273

slick in some form of net. Straw, for example, can remove up to thirty times its own weight of oil and is readily burnt afterwards. Siliconized sawdust or peat, india-rubber dust (Saugolit), expanded mica or vermiculite and volcanic glass (Ekoperl) have been used in Europe and are relatively inert (Sturz and Klein, 1964; Mann, 1966). They are also light and finely divided, presenting problems in spreading and recovery in open-sea conditions. Although it has the same limitations,

FIG. 12. A patch of oily emulsion from the ‘‘ Torrey Canyon ” lies on the bottom of a shallow sandy pool in Watergate Bay. Although some globules are rising to the surface, waves have already begun to cover the patch with sand (photo: A. Nelson-Smith).

an ingenious scheme for oil recovery minimizes problems of space and storage by utilizing shredded polyurethane foam. This can be manu- factured in a small boat by the reaction of two liquids. I n about 1 min, the mixture undergoes a hundred-fold expansion. 50 cu ft (28 litres) of foam, when shredded into approximately 1 in (2 cm) cubes and spread on the slick, absorb up to one ton of oil but remain afloat. Collected in a fine drag-net, 80% of the oil can be squeezed out between rollers after which the foam is used again (Anon., 196713; Mayo, 1968).

Solidification is another technique permitting the recovery of oil

274 A. NELSON-SMITH

spilt in calm conditions. Castellanos (1968) advocated the use of paraffin waxes or waste wax residues, sprayed at a temperature of 70°C. The addition of 15-20% wax will solidify crudes, although as much as 50-60% is needed for thinner oils. Similarly, spraying the slick with polyvinyl plastic in a volatile solvent covers the oil with a web of fine fibres; the necessary 15% ratio of plastic to oil is expensive, but the cost can be reduced by incorporating cheaper material such as waste textile fibre into the oil befors spraying it (Department of Scientific and Industrial Research, 1963b). During experimental use of this “ plastic moss ” in France, much of the spray blew away. Agglomeration was very efficient but difficulty was experienced in collecting the resultant raft (Rocquement, 1968). Such methods seem better suited to use on inland or drinking waters than at sea. Mechani- cal collection a t sea has been discussed in an earlier section (p. 227), but it should be mentioned that the French collected an appreciable amount of “ Torrey Canyon ” ‘‘ mousse ” by aligning a coastal tanker (the ‘‘ Petrobourg ”) at the downwind end of a V-boom. The emulsion accumulated in a layer about 2 f t (60 cm) thick along the ship’s side and was pumped aboard from a floating weir device (Holdsworth, 1968, and Spooner in the following discussion). A similar method of collection was tried in the Santa Barbara Channel early in 1969.

C. Problem8 in cleansing shores

One of the main lessons of the “ Torrey Canyon ” disaster is the value of advance planning. Although British government laboratories had been investigating methods of dealing with coastal oil spills for years before this (Department of Scientific and Industrial Research, 1961, 1963a; Zuckerman, 1968) the necessity of cleaning so much oil from so many miles of coast had never previously arisen. In retro- spect, it can be seen that some inaccessible coves need never have been treated. On most shores, far less of the solvent-emulsifiers could have been used and on others, mechanical methods would have been more effective. Since that event, local authorities throughout, Britain have been instructed to prepare oil-pollution plans (Beaumont, 1968 ; Ministry of Housing and Local Government, 1968). That other govern- ments have need of similar contingency plans is revealed, for example, by statements of U.S. Senator Muskie (1968) on the “ Ocean Eagle ” spill in Puerto Rico. Rocquement (1968) has referred to the French “ Plan Offset ”. British coastal laboratories and marine stations have been selected to act as emergency scientific or technical bases and maps have been drawn up defining those sections of coast which are of special value to biologists, fishermen or holidaymakers (Natural

THE PROBLEM O F OIL POLLUTIOS OF THE SEA 276

Environment Research Council, 1969). An analysis of this sort was made before deciding how to deal with a small spill of bunker oil near Plymouth (Holme and Spooner, 1968) which polluted a popular swimming beach, rocks which are visited by fair numbers of people and an extensive reef which is little used and supports a rich fauna and flora. It was decided to leave the latter area untreated, although there is still much controversy about the fate of such pollution. Those in charge of clearance operations are understandably concerned about the possi- bility of untreated oil floating off to re-pollute amenity beaches (see, e.g., Dudley, 1969). Observations on areas polluted but left untreated are not very informative; the deposits of oil removed by grazing molluscs in Milford Haven (George, 1961) and at Marazion, Cornwall (Smith, 1968), were fairly light. At Eleuthera in the Bahamas (Spooner and Spooner, 1968) i t had soaked into the porous coral rock, while in Lower California (North et al., 1964) the polluted cove is so isolated that the ultimate fate of the oil went unreported. " Torrey Canyon ') pollution was heavy enough to cause raasonable apprehension about re-pollution. On some untreated beaches in Brittany, oil deposits were still visible a year or more later (Zuckerman, 1968) and much of the oil from others was later carried to beaches previously cleaned. How- ever, according to some French authorities, " mousse "-type emulsions float off a polluted beach more readily than crude oil which has not been emulsified.

Where removal of the oil is necessary, a working guide has been provided by the Ministry of Technology (Wardley Smith, 1968a). Additional comments on the methods available have been made by Beynon (1968) and Mayo (1968). Wherever good access permits, mechanical collection is the method of first choice, using bulldozers, scrapers, powered or manual shovels and rakes for solidified material. Liquid oil in large quantities can be collected into pits or troughs and carted by gully-emptiers or sewage tankers. There are often backshore regions where trenches can be dug to receive this material, but the possibility of contaminating water supplies should always be borne in mind. Much of it could be burned in incinerators supplied with a compressed-air draught. Many of the absorbents used at sea can also be spread on a polluted beach, gathering the oily straw and other fibrous materials for burning but leaving deposits dusted with stearated rock- dust or siliconized ash to erode naturally or hosing them into the sea.

Thick deposits of fresh oil can be burned in situ, using flame- throwers or igniting either with " oxygen tiles ' ) or magnesium flares, but it is a slow process and may require the addition of extra fuel or oxidizing agents. Water-in-oil emulsions or oil floating on rock pools

276 A . NELSON-SNITH

will not burn readily. Portable oxy-propane burners will clean sea- walls and breakwaters, but only by causing the stone or concrete sur- face to flake. Steam-cleaning was attempted on some rocky shores in Brittany (Holme, 1967; Smith, 1968). The softened oil was carried away with water-jets, using a small quantity of surfactant or emulsi- fier. This is also slow and requires reasonable access for the portable boilers.

FIG. 13. ‘‘ Ploughing ” oily sand a t Sennen Cove with bulldozers. “ Strata ” of oil are As the tide rises, emulsifier will be sprayed onto the exposed in the foreground.

disturbed area (photo : A. Nelson-Smith).

Where it has been decided to accept the adverse biological conse- quences, solvent-emulsifiers are very effective in cleaning rocks. Ideally, the emulsifier mixture should be adjusted to suit the type of pollution. Thin fresh oil can readily be emulsified by the sparing use of one of the less toxic aliphatic solvents, whereas thick hardened deposits may require several applications of a highly aromatic solvent. I n each case, proper application involves the use of a fine high-pressure jet to ensure thorough mixing, followed by vigorous washing with water (either by hosing or the incoming tide) within half an hour. Greater delay or inadequate agitation results in the separation of a thin toxic

THE PROBLEM OB OIL POLLUTION O F THE SEA 277

oil which will probably pollute an adjacent area (Figs. 14 and 15). Even under the best of circumstances, the operation can result in a whitish plume of concentrated emulsion (Fig. 16) which may penetrate to a depth of 8-9 fm (17-18 m) and drift along the shoreline for several krn, affecting communities which had not experienced direct pollution

FIG. 14. A coralline pool near Porthleven, Cornwall. The encrusting species of Litho- thamnion and the tufts of Corallina officinalis have been bleached by the action of emulsifier, which also killed all the limpets; a dozen or more of their " homes " are visible as dark, roughly oval patches (photo : A. Nelson-Smith).

(Drew et al., 1967 ; Potts et al., 1967 ; Smith, 1968). Solvent-emulsifiers of the standard type are intended to be applied undiluted, although unsuccessful attempts to apply them in a water-jet through a foam eductor have been reported by Wardley Smith (I968b) and Crapp (1969a). Dispersants which can be applied in this way are ineffective in cleaning beaches (Moore, 1968). The fire-fighting services which normally provide the pumps used in hosing off the emulsion prefer to

A.M.R.-S 10

278 A. NELSON-SMITH

FIG. 15. A rock-pool a t Sennen Cove during cleansing operations ; note the algae (delicate red and brown) emerging from the milky emulsion. The tide did not flush this pool for several hours, during which time all its inhabitants were exposed to toxic concen- trations of emulsifier. In the absence of agitation, the emulsion has begun to break up, producing a thin black oil (background) which could float off to pollute other pools (photo : A. Nelson-Smith).

use fresh water in their equipment, thus imposing an additional stress on the shore fauna and flora.

Sandy beaches present special problems which have already been touched on (p. 239). Oil usually remains on the surface and is frequently concentrated towards the head of the beach by successive tides, when its mechanical removal is fairly simple, but heavy oil, " mousse ", or

FIG. 16. The tide, rising over an emulsifier-cleansed shore on the north coast of Cornwall near St. Ives, carries away a plume of emulsion and a thick crust of partly-separated oil (photo : A. Nelson-Smith).

280 A. NELSON-SMITH

partly sedimented oil are all liable to burial by wave-action. Spraying with emulsifier also tends to cause the oil t o penetrate deeper and may create a quicksand. British practice is to spray emulsifier while plough- ing or " rotavating " the sand, preferably only just ahead of the rising tide (Fig. 13), or to bulldoze the treated sand into the sea. I n Brittany, the French used the " German Machine " (Wyllie and Taylor, 1967 ; Wyllie, discussing Mayo, 1968) in which oily sand is roasted at a high temperature. The product, although dark grey in colour, is clean and does not stain. If there is advance warning of an approaching slick, it is possible to bulldoze a stockpile of surface sand to the head of the beach, providing clean material with which to cover any slight deposits remaining after treatment. Absorbents might also be spread in advance. Shingle and cobbles are more likely to trap oil and are less easy to '' cultivate ". The best that can be done is probably to spray emulsifier as vigorously as possible, just in advance of the tide. It will probably be necessary to apply many treatments. Sait-marshes are unlikely to be much used by the public, but as they are frequented by many birds the worst of the oil should be removed ; it is often sufficient to cut and burn the emergent parts of reeds and grasses.

D. Mode of action and toxicity of solvent-emulsij2ers

A certain amount of confusion has arisen from misuse of the term '' detergent ". Silsby (1968) pointed out that although this word applies to any agent which aids in cleaning, it has become restricted in popular usage to synthetic household washing agents, excluding soap. It is therefore particularly unfortunate that solvent-emulsifiers, so unlike domestic washing-up liquid, were referred to as " detergents " by the press and in some scientific reports during the " Torrey Canyon ) ' affair.

Synthetic household detergents came into widespread use after the Second World War and numerous investigations were made of their effects and toxicity, mostly upon fish and almost all in fresh water. Reports of these studies have been reviewed by Matulovh (1964), Prat and Giraud (1964) and Marchetti (1965a) and many are listed in a recent bibliography (Nelson-Smith, 196%). The surfactants which form the major part of these detergents are anionic (for example, alkyl or aryl sulphonates) and many are now " soft ", i.e. more or less bio- degradable. Those used in solvent-emulsifiers are non-ionic (for ex- ample, alkyl phenol-ethylene oxide condensates) and are mostly " hard ') or not readily degraded, According to Jones (1964) and Mar- chetti, non-ionics are slightly less toxic than anionics, for which toxici- ties to a variety of fish species fall within the range 1-100 p.p.m. The

THE PROBLEM OF OIL POLLUTION OF THE SEA 281

constitution of the surfactant molecule is important ; the lethal concen- tration of a nonyl-phenol polyoxyethylene condensate to goldfish Carassius auratus (L.) after 6 h exposure ranges from 5 p.p.m. to 2 500 p.p.m. according to the ratio of ethylene oxide to nonyl phenol units (Marchetti, 1964, 1965a). Sublethal effects observed from anionic surfactants a t 0.5-10 p.p.m. include erosion of gill epithelia and destruction of mucous cells (Schmid and Mann, 1961; Scheier and Cairns, 1966) or damage to the chemical senses (Bardach et al., 1965). These result in loss of equilibrium, convulsions and respiratory difficul- ties (Maldura, 1961) or an inability to detect food (Foster et al., 1966). Mann and Schmid (1961) found that a t 5-10 p.p.m., anionic surfactants immobilize the sperm of trout Salmo trutta, reduce the fertilization rate and kill fertile eggs. According to Marchetti (1965b), the fry of rain- bow trout S. gairdneri are most resistant to nonyl-phenol polyoxyethy- lenes when newly hatched (42 p.p.m. is toxic in a 6 h exposure). Their maximum sensitivity (to 2 p.p.m.) is reached as the yolk-sac is ex- hausted, but is slightly reduced in older (fingerling) stages to just over 5 p.p.m. The larvae of marine clams Mercenaria mercenaria and oysters Crassostrea virginica are more sensitive than adults, showing develop- mental defects a t 0.14-3.0 p.p.m. of anionic and 1-0-5.0 p.p.m. of non- ionic surfactants (Hidu, 1965). Matulov8 (1964, 1966) has tested a variety of surfactants on species of the micro-algae Chlamydomonas, Scenedesmus and Chlorella. A non-ionic compound showed unfavourabie effects on growth at 5 p.p.m. and was lethal a t 200 p.p.m., but had a slight stimulating effect a t concentrations below 2 p.p.m.

Surfactants form only one part of mixtures for dispersing oil spills and are often the least toxic component (see pp. 284, 287). Chadwick (1960) tested the toxicity of an American solvent-emulsifier (Tricon) to striped bass Roccus saxatilis (Walbaum) and found it lethal in 5-10 h at 10 p.p.m. George (1961) reported the drastic effects of emulsifier cleansing after a spill in Milford Haven at about the same time as the Ministry of Agriculture, Fisheries and Food shellfisheries laboratory at Burnham-on-Crouch was investigating the toxicity of a number of cleansers to molluscs and crustaceans of commercial importance (Depart- ment of Scientific and Industrial Research, 1961 ; Portmann and Connor, 1968 ; Simpson, 1968b). Preliminary tests intended to simulate con- ditions during the cleansing of a shellfish bed showed that a brief immersion in 25% suspensions of four emulsifiers caused unacceptable mortalities (up to 96% in cockles Cardium edule) ; this led to an official recommendation not to spray oyster layings or cockle beds. The edible winkle Littorina littorea (L.) appears to be extremely resistant, as was confirmed by Crapp (1969a) ; the winkle showed a mortality of only

282 A. NELSON-SMITH

5% after one hour’s immersion in undiluted B P 1002, while that of topshells and other winkles lay between 75% and 100%. Mortality of the topshell Monodonta lineata was less than 20% after treatment with 80% BP 1002. Littorina obtusata and Gibbula umbilicalis (da Costa) were the most sensitive in these tests, with L. saxatilis, G. cineraria (L.) and the dog-whelk Nucella lapillus (L.) showing an intermediate response. Simpson offered as a partial explanation of differences in bivalve sensitivity the “ persistent gape ” of cockles, which do not close completely as do oysters (Ostrea edulis) and mussels (Mytilus edulis). Crapp applied the emulsifier to actively crawling gastropods, but noted that mortalities are much lower if they are first shaken to make them close tightly. Spooner (1968a) suggested that a heavy dose of emulsifier might have less effect than a light one, because it stimu- lates those animals which can to close up quickly. Crapp also reported marked seasonal changes ; for example, L. obtusata collected at the end of the winter were exceptionally sensitive.

Perkins (1968a) also studied the effect of brief exposure to a high concentration (25%) of various emulsifiers which only some winkles and whelks survived. He found that the median lethal concentration of BP 1002 over 24 h is greater than 3 000 p.p.m. for Littorina saxatilis, greater than 2 000 p.p.m. for L. littorea, 1 000 p.p.m. for Nucella and 250 p.p.m. for L. obtusata. Mytilus is fairly resistant a t 90 p.p.m. over 24 h, but in a 96 h test its LC,, dropped to 2.5 p.p.m. ; the sea-star Asterias rubens survived 40 p.p.m. and the shore-crab Carcinus maenas, about 30 p.p.m. The other common shore animals which he tested are even less resistant. Portmann and Connor showed much the same results. Hermit crabs Eupagurus bernhardus (L.), brown shrimps Crangon crangon and pink shrimps Pandalus montagui are particularly sensitive (LC,, about 5 p.p.m.). Tests a t the Plymouth laboratory (Smith, 1968) revealed that a variety of sublittoral crabs are killed by BP 1002 at 5-25 p.p.m., bpt molluscs failed to survive one-tenth these concentrations. Wilson (1968a) found that larvae of the tubeworm Sabellaria spinulosa Leuckart were killed within a day or two by 2.5 p.p.m. of this emulsifier. Although irritated by 0.5-1.0 p.p.m. they apparently survived, but later became unhealthy and died in 4-6 weeks. Corner et al. (1968) found that adults of the barnacle Elminius modestus are killed by 10-100 p.p.m., although 5-10 p.p.m. slows down their feeding; 3p.p.m. slows down the swimming of the settling (cypris) larvae but, again, only 0.5-1.0 p.p.m. inhibits the development of younger (nauplius) larvae. Developing his earlier work, Perkins (1968b) showed that whelks Buccinum undatum, which had apparently recovered from brief immersion in 25% emulsifier, died as much as four

THE PROBLEM OF OIL POLLUTION OF THE SEA 283

months later without making further growth. The growth of Littorina littorea is detectably limited at 7.5 p.p.m. (one-four-hundredth of the LC,,) and significantly inhibited a t 30 p.p.m. (one-hundredth of the LC,,). At a cellular level, Manwell and Baker (1967) have demon- strated powerful effects on enzymes and other proteins (e.g. it binds the haemoglobin of soles Solea solea (L.)) but used only high concen- trations. Corner and his colleagues also made preliminary experiments with tissue extracts from Mytilus edulis, Patella vulgata and Chlamys opercularis (L.). They found that emulsifiers kill these molluscs at 10- 100 p.p.m., but concentrations around 1 000 p.p.m. were needed to in- activate their enzymes by more than 50%. They suggested that physical effects must therefore also be involved in the toxicity. Hicks and Chaplin (unpublished, 1969) also found that 6 000 p.p.m. of BP 1002 inactivated various enzymes of Carcinus by only about 60%.

Fewer laboratory studies have been reported on the sensitivity of plants to emulsifiers. George (1960; unpublished but quoted by Nelson-Smith, 1968a) added Polyclens to rock pools at 0*2%, killing most of the algae, but observed that the corallines eventually recovered from an addition of 1%. Boney (1968) found that the reproductive bodies of Ascophyllum nodosum (typical of the large fucoids) are killed only at high concentrations of emulsifiers (25% or more) although free spermatozoids are inactivated in 9-150 p.p.m. The green algae Clado- phora rupestris (L.) Kiitz. and Bryopsis hypnoides Lamour., together with the microscopical form Prasinocladus m r i n u s (Cienk.) Waern and the small filamentous red alga Acrochaetium infestans Howe & Hoyt are damaged or killed at 25-50 p.p.m. Boney was unable to demon- strate that undiluted emulsifiers did any harm to Polysiphonia lanosa (L.) Tandy or the laver-weed Porphyra umbilicalis. Rather more anec- dotal evidence from O’Sullivan and Richardson (1967a, b), Spooner (1967) and Nelson-Smith (1968a) of decolorized and flaccid plants of Porphyra, as well as of the large brown alga Himanthalia elongata, species of Cladophora, Ulva and Enteromorpha, and corallines (Corallina oficinalis L. and Lithothamnion spp.) suggests that damaging concen- trations were none the less attained during ‘‘ Torrey Canyon ” cleansing operations. 0.25-0.5y0 BP 1002 altered the colour of pigment extracts from the red alga Calliblepharis jubata (= C. lanceolata (Stackh.) Batt.) in experiments by Manwell and Baker (1967). The sublittoral Delesseria sanguinea (Hds.) Lamour was killed by as little as 0.001 yo (10 p.p.m.) in tests reported by Smith (1968) and showed unusual colours at some depth and distance from the shore (Drew et al., 1967; Potts et al., 1967). Phytosocial analyses by Bellamy et al. (1067) have also demonstrated damage to sublittoral as well as intertidal algae. Unlike the plants

284 A. NELSON-SMITII

observed by George, the coralline algae lining rock-pools which were whitened by emulsifier treatment on many Cornish shores (Fig. 14) showed little sign of recovery (Nelson-Smith, 1968b) ; the gradual re- turn of pink and purple colours to these pools was more probably due to recolonization.

Damage to lichens and maritime plants on the strandline or cliff ledges after the " Torrey Canyon " spill was probably due mainly to emulsifier spraying (Ranwell, 1968b). Clifftop and bacltshore vegeta- tion was certainly killed by the spillage of undiluted cleansers, some- times over a large area (Ranwell, 1968a). Tests on turves of Puccinellia maritima (Baker, 1968) show that 10% BP 1002 is damaging, but only the undiluted emulsifier kills i t completely. Not only are non-ionic surfactants bacteriologically " hard " ; the type used in B P 1002 is actually recommended for use in mixtures to suppress bacterial decom- position of stored oils (Davis, 1967). It is thus not surprising that the emulsifiers used in Cornwall kill most oil-degrading bacteria at 10 p.p.m. Nevertheless, some survive 100 p.p.m. or more. These multiply rapidly, utilizing the emulsifier solvent and probably also the oil dissolved by it. Samples treated with 1 000 p.p.m., however, became sterile and re- mained so (Gunkel, 1968 ; Smith, 1968).

The aromatic solvent used in BP 1002 and similar cleansers is more toxic than the surfactants or other components, as reported by Smith, Crapp (1969a) and other authors. A scattered literature on the toxicity of aromatic hydrocarbons has already been reviewed above (see pp. 249-256). Corner et al. (1968) found that BP 1002 solvent is very nearly as toxic to barnacle larvae as the mixture, other components having markedly less effect. However, although Wilson (1968b) demonstrated that some material, toxic to polychaete larvae, remains on sand grains for some days after their treatment with emulsifier and subsequent thorough washing, experiments described by Smith (1968) show that the solvent is readily volatile. Solutions of emulsifier from which i t is free to evaporate become increasingly less toxic. Small soles (Xolea solea) suffer lOOyo mortality after 24 h in water containing 50 p.p.m B P 1002, but if their introduction to the tank is delayed by 24 h this mortality drops to 30%. After 48 h it is 10% and after 72 h the water has become non-toxic (Portmann and Connor, 1968 ; Simpson, 1968).

It is now generally recognized that cleansing with solvent-emulsifiers inflicts more biological damage than the original pollution. George (unpublished ; see Nelson-Smith, 1967a) estimated that after a 1960 spill in Milford Haven, approximately 30% of shore life was damaged by the oil alone whereas 90% was killed after emulsifier cleansing. Cowell (1969b ; see also Crapp, 1969) found that 38% of the cordgrass

THE PROBLEM OF OIL POLLUTION O F THE SEA 285

Littorina neritoidos

L obtusata (JUV)

barnocle spot

Chthamalus stellatus

b l o w s balanoides Nucella lapillus Ocenebra erinacea Actinia equina Mmodonta Iineata Gibbula umbilicalis G. cineraria Patella vulgota P asppra Mytilus edulis Pomatoceros triqueter Spirarbis corallinae 5 borealis S rupestris sponqeb Lichina pygrnaea

Parphyro umbilicalis

k lve t ia canaliculato

Fucus spiralis

Ascophyllurn nodosum

Fucus vesiculosus

F serratus Halidrys siliquosa Cladophora rupestris Colpomenia pereqrina Enteromrpha spp.

f

Ulva Iactuca Codium fragile

Catenello repens Coral1 ina of f ic inal is

Laurencia pinnatifida

Gigortina stellata

Himanthalin elongata

Laminaria spp

- 1 . 1 . . . . . E m 'D 2 2 9 lm 0 * A

c_

C

.evesic.

FIG. 17. The distribution of common animals and plants on two shores in west Cornwdl, resurveyed six months after '' Torrey Canyon " pollution and cleansing. Open (white) histograms show the situation just after the disaster ; black histograms superimposed on thess indicate survival. Many of the animals previously present had been killed and washed away before the original survey, leaving no record. Stippled histograms show settlement since the first snrvey-mainly barnacle spat and green algae (from Nelson-Smith, 1068b).

286

.

-

A. NELSON-SMITH

-MHWN

M T L

MLWN

.MLWS

, I 1 27r l J a n 67

25 - 23 -

21

19 - 17 -

15

13

I1

-

- - -

Littorina neritoides

feet occasional above chart datum

Littarina saxatills

Littorina littorpo

Jan67-

9 -

7 -

5 -

3 -

FIG. 18. The distribution and abundance of some common winkles and topshells on a shore at Hazelbeach. Milford Haven. Repeated surveys by Nelson-Smith (1967b, 1968a, 1968b) and Crapp (1969a) show the effects of oil-spills from the " Chryssi P. Goulandris '' (Jan. 67) and the Gulf refinery (Nov. 68). Redrawn from Crapp.

Spaytinu townsendii was killed by a spill of fresh crude oil, but the mortality rose to 55% where emulsifiers were also applied. Many reports based on " Torrey Canyon " experience make the same point -for example, O'Sullivan and Richardson (1967a, b), Nelson-Smith (1968a, b), Ranwell (1968a), Smith (1968) and Wardley Smith (1968a- c). Apart from their immediate toxic effects, emulsifiers spread the pollution to the crevices and landward or leeward surfaces which all but the heaviest oil pollution fails to reach. They also distribute the oil in fine droplets throughout the depth of rock pools and coastal

THE PROBLEM O F OIL POLLUTION OF THE SEA 287

shallows (Figs. 15 and 16). Such droplets are readily taken into the food-stream by filter-feeders (see, for example, Spooner, 1968a) and may be better able to " wet " exposed animal tissues. On the worst- affected sites in Cornwall, solvent-emulsifiers applied liberally, in conjunction with heavy oil pollution, killed every limpet on the shore, bringing about the changes in algal cover described above (p. 261 and in Fig. 17).

Perkins (1968a) offered the opinion that an oil emulsion containing B P 1002 is more toxic than the emulsifier alone. This is probably true where the surfactants help the oil to penetrate-the oil then carries in with it the toxic elements in the emulsifier. Portmann and Connor (1968) found that the addition of twice its volume of oil to Polyclens almost doubles its toxicity to cockles Cardium edule and renders i t slightly more toxic to brown shrimps Crangon crangon, although BP 1002 and Gamlen become less toxic when treated in this way. Van de Wiele (1968) discovered that emulsions of Finasol possess the same toxicity to the brine-shrimp Artemia salina (L.) and the guppy Lebistes reticulatus (Peters) whether or not crude oil (which by itself had little effect in her tests) is added. Preliminary experiments a t Swansea using yeast in a microrespirometer indicate that the addition of an equal amount of fresh crude oil to B P 1002 approximately halves its toxicity, which is here exerted at the surface of the test organism. Presumably the oil binds some of the toxic elements, effectively removing them from the culture solution.

Since the " Torrey Canyon " disaster, manufacturers have striven to reduce the toxicity of their emulsifiers, either by diminishing the proportion of aromatics in the solvent or by eliminating hydrocarbon solvents altogether. Test blends of B P 1002 in which the solvent contains a high proportion of aliphatic compounds are considerably less toxic to gastropod molluscs (Crapp, 1969a) and yeast cultures (un- published; Fig. 19). Finasol is a similar reformulation of Fina Unisol. Tests by Capart (1968) show that it is highly toxic a t 0.1% and at 100 p.p.m. it is still somewhat toxic to guppies, brine-shrimps, a fresh- water snail Planorbis sp. and Daphnia pulex Degeer, but not to protozoans or other micro-organisms. At 10 p.p.m. it is entirely non- toxic.

The water-soluble dispersants Polycomplex-A and Corexit 7664 have been compared with various more conventional emulsifiers by Spooner and Spooner (1968) and Spooner (1968a). Polycomplex-A appears to be approximately one-fifth as toxic as B P 1002 to a selection of marine organisms. Corner (quoted by the Spooners) found it twelve times less toxic in similar tests on barnacle larvae. Corexit, however, is less toxic

288 A. NELSON-SMITH

by several orders of magnitude. Spooner (1968a) found that concen- trations at least up t o 1 000 p.p.m. are safe for mussels Mytilus edulis. Griffith (1969) reported that the median toxicity for limpets Patella vulgata is 1 000 p.p.m, while for the winkles Littorina littorea and L. obtusata it lies between 1000 and 10 000 p.p.m. (0-1-1.0%). I n its sublethal effects on yeast cultures, Dispersol 0s appears to be about 500 times less toxic than BP 1002. Corexit or Dispersol are obviously the dispersants of choice for use at sea, but comparisons with BP 1002 a're informative rather than practical, since they are both ineffective

HIGH-AROMATIC EMULSIFIER LOW-AROMATIC EMULSIFIER -Q~e

4 0 0 p g . Oxygen consumed

4 0 0 p g Oxygen consumed

2 0 0

0

0 2 0 40 60min . ,/ , 2 0 ~ 4,O ~ 6Prnin.

FIG. 19. Respiration of standard yeast cultures in vnrious concentrations of BP 1002 (left) and a test-blend containing a much more aliphatic solvent-mixture. Individual curves have been superimposed so that the points a t which the sample wns intro- duced coincide; the axes are calibrated from that point (unpublished, Dunn and Nelson-Smith, 1969).

against oil stranded on the beach. The new BP 1100 appears to be useful in both situations and to have the same very low toxicity.

VI. CONCLUSIONS AND PROSPECTS I n summary, the increased use of petroleum products (in the syn-

thetic chemical industry even if internal-combustion engines eventually become obsolete) will continue to demand the large-scale transport of crude oil, much of it a t sea in even larger bulk carriers, with an atten- dant degree of unavoidable spillage. Sturmey (1967) has predicted a doubling of world oil consumption every ten years at least until the end of this century. Pressures from responsible operators within the oil industry, as well as from official and unofficial bodies outside it, must ultimately bring about the universal adoption of every possible

THE PROBLEM OF OIL POLLUTION OF THE SEA 289

method of reducing such spillages. An important aspect of this is the development of efficient methods for apprehending vessels which deliberately discharge oily wastes and the successful prosecution of their owners or operators. It is also important that international agreement be reached on the rights and responsibilities both of ship operators and those countries whose coastal waters are threatened by the wreck of a vessel carrying heavy oils-or, indeed, even more hazar- dous cargoes. The probable path of a slick can now be predicted with reasonable accuracy, provided that proper observations are kept and accurate meteorological data are speedily provided. With equipment now available for military intelligence, it should be possible to main- tain continuous surveillance of quite small slicks far out at sea from high-flying aircraft or satellites (see Cronin (1965) and more recent NASA press releases). It is now accepted policy to treat the oil at sea wherever possible. The means to do this efficiently and with little damage to marine life by sinking, dispersing or mechanical re- moval (where weather conditions permit) are now known and require only the organization to get them to the right place in time and in sufficient quantities. The drastic effects of ‘‘ first-generation ” emul- sifiers effective on stranded oil have been well documented. As Sennen Cove’s Rural District Councillor said (having done his share in cleansing Whitesand Bay from “ Torrey Canyon ” oil) “ no one in his right mind would use detergent . . . if any other effective method was available ” (see Cowan, 1968). Unfortunately, many thousands of gallons of these emulsifiers are now stockpiled against an emergency spill by local authorities throughout Britain. To replace these with newer, more expensive formulations would be very costly although, in emergency, it is with the earlier mixtures that enthusiastic but uninstructed volun- teers can do great if unwitting damage.

The responses of shore biota to catastrophic pollution in Milford Haven and Cornwall show that partial recovery occurs quite quickly in regions where populations are both plentiful and varied (Fig. 18). Like any other abnormal stress, oil pollution has a particularly marked effect on organisms near the limits of their geographical range. Zoo- geographical and seasonal differences account for some of the dis- crepancies which exist between the various accounts of mortalities observed on affected shores or recorded in laboratory experiments. A good example is the topshell Monodonta lineata, which was found to be very resistant in Cornwall but, farther north in Milford Haven, serves as a sensitive indicator of shore damage and showed marked seasonal variations in susceptibility during an extended series of toxicity tests. The disproportionate effects that oil pollution and its cleansing have

290 A. NELSON-SMITH

on grazing molluscs and the algal cover which they normally control indicate that in regions where this is repeated too often, rocky shores might become permanently covered with a slippery and unsightly growth of seaweeds, while adjacent sandy shores could lose the services of those scavengers which usually remove unpleasant debris. Thus the amenities which repeated (‘ cleansing ” is intended to preserve might, in the long term, suffer ever1 greater damage.

Outstanding problems in the purely biological and technical fields of oil pollution have been summed up by Arthur (1968). Concluding his account of the part played by the Plymouth laboratory in the ‘( Torrey Canyon ” affair, Smith (1968) called for a higher degree of co-ordination between government agencies, the oil and shipping industries, and biological interests ; Lord Geddes, summing up the scientific deliberations of the Rome Conference (1968), extended this plea to the international field. Administrative and legislative action, although always lagging well behind scientific discovery, is neverthe- less essential to its practical application and control and there are significant advances to be rnade in this area, too. Dr. Giovanni Spa- gnolli said, in closing that Conference, “ technical progress threatens to upset the normal balance of nature and the adoption of legal, technical and administrative measures to prevent and check pollution is a matter of urgency ”.

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