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The Rocky ShoreRocky shores are diverse and dynamic ecosystems where the inhabiting communities survive between

two worlds – the sea and the land

The familiar shoreline or littoral region is that area of shore which lies between the high-water mark and the low-water

mark of spring tides

These littoral zones may differ greatly from one another as local geology, wave action and aspect, influence the

structure of the shoreline

Living organisms in these intertidal regions face continual fluctuating environmental conditions as they are subjected

to cyclic exposure and submergence from tidal activity

The distribution of life on the littoral shore reflects the development of specialised structures and tissues that adapt

the different species to the prevailing conditions

Differences in exposure to the force of the waves have a modifying effect on the communities

inhabiting sheltered and exposed shores

Diversity on The Rocky ShoreThe sheltered rocky shore provides a variety of

habitable environments where the diversity and the composition of species can be related to their

positions on the shore

The exposed rock faces, cervices and intertidal pools provide habitats for a range of species that display adaptations to the

local prevailing conditions

The sheltered rocky shore described here is located on the east coast of North Yorkshire where encrusting barnacles and

mussels and seaweeds dominate the shore

The following discussion describes the findings of a group of students who surveyed the shore and who carried out a number of investigations based upon their observations

The Lower ShoreEnvironmental conditions on the lower shore are

less harsh and relatively stable as surface populations are never uncovered by the tide for more than a few hours at a time

Species diversity is high on the lower shore and competition for food and space is fierce

Fucus serratus (toothed-wrack) is the dominant brown alga of the lower shore and is intolerant of desiccation

(cell wall thickness 0.45 m)

Red algae are intolerant of desiccation and form dense turfs beneath the carpet of Fucus serratus; these algae are tolerant of shade and possess the additional pigment (phycoerythrin)

for efficient photosynthesis at low light levels

Sponges, anemones, sea slugs, blenny fish and shrimps occupy this zone alongside many other species of animals and algae

The Laminaria ZoneThe Laminaria Zone is occupied by species that are

rarely uncovered by the tide but are subjectedto intense wave action

Environmental conditions in this zone are relatively constant and productivity is high; this is the least harsh area of the

rocky shore providing niches for the establishment of alarge diversity of organisms where competition is fierce

The kelps (Laminaria species) are the dominant brown algae of this zone where they form underwater ‘forests’

displaying prolific growthThese giant algae are intolerant of desiccation and possess

flexible stipes that attach firmly to the ocean bottomwith their powerful holdfasts

Starfish, brittle stars, marine worms and sea urchins are found feeding in this zone

Numerous, shade-tolerant species of red algae are found growing among the kelps

Zonation and DiversityThe zonation of both plants and animals observed on this

sheltered shore reflected adaptations to different environmental conditions, with diversity increasing from

the harsh upper shore to the less harsh lower shore

The brown algae displayed a distinctive zonation pattern that related largely to their ability to resist desiccation

and to photosynthesise effectively

Brown algae have developed specialised structures and tissues for reducing desiccation, anchoring themselves to the rocks and ocean bottom, and photosynthesising effectively

Brown algae are distinguished by the presence of the accessory pigment, fucoxanthin; this brown pigment enables

the algae to absorb blue-green light(the wavelengths that penetrate deep into the water)

The holdfast at the base of the stipes of these brown algae anchors them to the rocks

Zonation patternof brown seaweeds

on the shelteredrocky shore

Organisms inhabitingthe upper shore are

subjected to fluctuatingenvironmental conditions

and the drying effectsof the air during the

tidal cycle

A group of students investigated the distribution of brown algae along a

sloping sheltered rocky shoreA transect was laid down along the

shore by laying a tape, at right angles to the sea, from the splash

zone to the low water mark (LWM)A one metre, square quadrat frame

was used to determine the percentage cover of algae at two-

metre intervals along the tapeA five-point abundance scale was

used to record the percentage cover of algae within each frame

Abundance scale % Cover

1 < 5%

2 5 – 25%

3 >25 – 50%

4 >50 – 75%

5 75%

Species of Brown Algae Pelvetia

canaliculata Fucus

spiralis Fucus

vesiculosus Fucus

serratus Laminaria

sp.

Splash zone

18

HWM 16 2 1 Upper Shore 14 5 2 2

12 2 4

10 3 3

8 5 2 1

6 4 1 2

Middle shore

4 1 2 4

2 1 4 3 Lower shore

Distance from low

water mark (m)

LWM 0 1 3 5

Transect Results

• Draw kite diagrams to illustrate the distribution of algae along the shore

• Discuss the pattern of distribution displayed by the different species of algae

• Suggest reasons for the pattern of distribution observed

Fucusspiralis

Fucusvesiculosus

Fucusserratus

Laminariasp.

Pelvetiacanaliculata

0

2

4

6

8

10

12

14

16Upper shore

Middle shore

Lower shore

Kite Diagramfor rocky shore

transect

Brown Algae and Desiccation

Students collected samples of three different species of brown algae in containers of seawater

and returned them to the laboratory for further investigation

Each group of students collected three samples of Fucus serratus, Fucus spiralis and Fucus vesiculosus

After blotting off the excess seawater, all the samples were weighed and their initial masses recorded

Clamp stands and string were used to construct ‘washing lines’ to which the algae were then attached

The algae were weighed every thirty minutes for the first two hours and then hourly for a further three hours

The percentage fresh mass at each time interval was calculated for each species and the group results were pooled

The mean percentage fresh mass was determined and the results presented graphically

Time (mins) Mean Percentage Fresh Mass

Fucus spiralis Fucus vesiculosus Fucus serratus

0 100 100 100

30 93.14 87.33 81.32

60 84.79 78.08 73.62

90 77.77 73.13 66.61

120 72.69 61.73 54.97

180 62.47 54.36 47.36

240 56.32 48.75 42.36

300 51.44 44.22 38.57

Pooled Results

Construct a graph of the data obtained

Mean % Change in Mass against Timefor different species of brown algae

Relate these results to the zonation pattern of the algae