T A N E 29, 1983

A G U I D E T O A L G A E IN O X I D A T I O N PONDS IN T H E A U C K L A N D DISTRICT

by Vivienne Cassie Botany Division, Mt Albert Research Centre, DSIR, Private Bag, Auckland.

S U M M A R Y

Seventy species of pigmented freshwater algae have been identified from smaller oxidation ponds in the Auckland district, and from the North Shore Purification Works at Albany. Green algae, including euglenoid flagellates, predominated in the phytoplankton at most times of year. Blooms of blue-green algae have been recorded from some ponds in late summer.

INTRODUCTION

Freshwater algae can be either beneficial or harmful, depending on their function and the species concerned (Cassie 1979). In the upper layers of healthy oxidation ponds there exists a host of extraordinarily beautiful algae which are nearly always beneficial. Without their presence and efficient functioning as oxygen producers the ponds would not become purified, and the health of people dependent on oxidation ponds for sewage disposal would be at risk. In the vicinity of Auckland, green algae, including species of Euglena, dominate in healthy ponds for most of the year. Blooms of harmful blue-green species may occur towards the end of summer in the absence of high winds which cause overturn, and with a rise in water temperature above 23°C. Microcystis aeruginosa sometimes produces a toxin which can cause death of animals, and be unpleasant if ingested by humans. Death of animals may also occur due to anoxia, resulting from the spread of a scum on the surface. Artificial aeration may be necessary to break up such blooms.

Several detailed surveys have already been made on algae in oxidation ponds in the Auckland district (taxonomy: Haughey 1968, 1969, 1970; ecology: Haughey 1970, Hutchinson and Oliver 1978; physiology and chemistry: Brockett 1973, Vincent and Silvester 1979a, 1979b; population statistics: Rowe unpublished 1975). Further information may be obtained by consulting these works, all of which are available in the Biological Sciences Library, the University of Auckland.

POND S U R V E Y 1977-1982

Records in Appendix I were compiled from a microscopic examination of samples collected by Deirdre A . Oliver, Auckland Regional

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Authority, and by the author from oxidation ponds at Albany, North Shore, Auckland, from 1977 to 1981.

Green algae were the most prominent class, with 38 species. Euglenoid flagellates were also well represented, with 14 species. Diatoms, more restricted in occurrence, provided 8 species; blue-green algae, 5 species; chrysophytes 3 and cryptophytes 2 species. Details of the commoner algae with their seasonal occurrence, abundance (in cells/ml x 10s) and light penetration (secchi disc measurements) can be found in Hutchinson and Oliver (1978).

Euglena acus, ubiquitous in Mangere sludge lagoons and Albany ponds (Haughey 1968, 1970), was scarce or absent from ponds at Helensville, Waiwera, Wellsford, Wesley College and Waiuku. Euglena minuta was recorded only from those at Snells Beach. Cryptomonas erosa, dominant at times in the ponds at St Stephens and Wesley Colleges, was not recorded from the Albany ponds.

Diatom dominance varied greatly from one pond to another. At Albany diatoms seldom outnumbered green algae in the main settling ponds, but were more abundant in the smaller ornamental pond outside the laboratory, which was also supplied with polluted water. Blue-green algal blooms also varied. Oscillatoria platensis (at first straight, later curved) formed extensive mats at the surface in the Albany ponds but was not accompanied there by Microcystis aeruginosa, as in ponds to the north of Auckland at Wellsford, Waiwera, Orewa and Helensville. Anabaenopsis circularis (a new record for New Zealand) was recorded, in vast numbers, only from Waiwera ponds. Dinoflagellates and red algae were absent from all samples examined.

P R A C T I C A L G U I D E TO F I E L D A N D L A B O R A T O R Y STUDIES

Methods of collection Lower a plastic bucket on a rope from a boat or a jetty as far out from

the fringe of the oxidation pond as possible, preferably near an aerator. A small wide-mouthed container 300-500 ml in volume will normally provide a representative selection of algal species present at the time of sampling. Wear rubber gloves and do not handle or ingest any of the pond liquor in case harmful organisms are present. Keep the jars cool, transfer them to the laboratory and examine contents as soon as possible after collection. Place samples in clear glass containers on a laboratory bench near a window away from direct sunlight. Motile forms will swim up to the surface. Do not keep sample more than three days, since bacteria increase rapidly at the expense of the algae. Boil or sterilize all glassware after use.

Mounting Select an area of the glass container where algal cells have

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accumulated and remove a drop with a pasteur pipette, using a rubber bulb on the end. Do not suck up the liquid with the mouth. Release the drop on to the centre of a clean glass slide and place a coverslip over it, removing any surplus liquid oozing out from the edges with a tissue or filter paper.

Examination Place the slide, coverslip uppermost, on the microscope stage and

leave it for a few minutes while swiftly moving algae slow down. Activity amongst the flagellated forms will be intense at first, making observation difficult except at low magnifications. Work under as low a light intensity as possible, since motile cells tend to move away from bright light. A compound microscope equipped with X10, X25 and X40 objectives is essential; a X100 oil immersion objective is an added advantage. Phase and interference contrast attachments greatly facilitate critical observations, also reducing eyestrain. If phase contrast is not available, shut down the condenser iris diaphragm two-thirds to give a clearer image.

Identification Make drawings and measure cells in micrometers with the aid of a

slide and an eyepiece micrometer. Compare your findings with descriptions and illustrations in a textbook on freshwater algae. Useful introductory publications are " A beginners guide to freshwater algae" (Belcher and Swale 1976), "River phytoplankton" (Belcher and Swale 1979), and "Algae and water pollution" (Palmer 1980). More advanced texts are those of Prescott (1962) and Whitford and Schumacher (1973).

K E Y TO C L A S S E S OF P I G M E N T E D A L G A E IN O X I D A T I O N PONDS IN T H E A U C K L A N D A R E A

Cells without definite chloroplasts and nuclei, often blue-green C Y A N O P H Y C E A E ( C Y A N O B A C T E R I A )

Cells with definite chloroplasts and nuclei, often green or yellow-brown 2 Vegetative cells yellow-brown 3 Vegetative cells grass-green 4 Cells not box-like C H R Y S O P H Y C E A E Cells box-like 5 Vegetative cells bounded by a rigid cell wall, food reserves starch (turning blackish-blue with iodine) E U C H L O R O P H Y C E A E Vegetative cells not bounded by a rigid cell wall (often changing shape); food reserves not starch E U G L E N O P H Y C E A E Cells not motile, without flagella (walls rigid, overlapping, patterned)

D I A T O M O P H Y C E A E Cells motile (furrowed, with two unequal flagella and two elongate chloroplasts)...

C R Y P T O P H Y C E A E

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K E Y T O G E N E R A A N D S P E C I E S

(After Prescott 1962, Haughey 1968, Whitford and Schumacher 1973, Belcher and Swale 1979, Palmer 1980).

E U G L E N O P H Y C E A E

1. Cells attached to small animals Colacium vesiculosum Cells planktonic 2

2. Cells motile, changing shape (i. e. metabolic) 3 Cells motile; walls rigid 4

3. Cells somewhat elongated; food reserves rods or spheres Euglena Cells broadly ovoid; food reserves in two large rings Lepocinclis (L. texta)

4. Cells spherical or oval; walls smooth or spiny, often orange Trachelomonas Cells twisted or flattened, often with a pointed tail Phacus

Euglena

1. Cells spindle-or pear-shaped, less than 70 um long 2 Cells cylindrical or spindle-shaped, more than 70jum only 5, 6

2. Cells spindle-shaped, up to 60 pm long; posterior ends blunt; chloroplasts ribbon­like, radiating E. viridis Cells of a different shape 3

3. Cells up to 60 p. m long, green, pear-shaped, strongly metabolic (i. e. changing shape) E. gracilis (Fig. Ib)

Cells up to 15 Jim long 4 4. Pellicle not striated, chloroplasts single, plate-like E. minuta

Pellicle striated 5 5. Cells red, spindle-shaped, up to 103 jim long, pellicle faintly striated

E. haematodes (Fig. lc) Cells green, cylindrical, up to 130 um long; pellicle prominent with bead-like striations E. Spirogyra

6. Tail sharp, food reserves (paramylon) in rods; chloroplasts disc-shaped E. acus (Fig. Ia)

Tail blunt, food reserves not rod-shaped 7 7. Cells cylindrical; chloroplasts 2, ribbon-like, radiating from the centre (paramylon

lens-shaped) E. geniculata Cells not cylindrical; chloroplasts not ribbon-like 8

8. Cells green, up to 35 um long, almost cylindrical, strongly metabolic; chloroplasts 2, plate-like; eyespot yellow E. agilis Cells red, up to 150 jum long, broadly spindle-shaped, weakly metabolic; chloroplasts many, elongate; eyespot red E. sanguinea

Phacus

1. Cells with spiral striations 2

Cells with longitudinal striations 3 2. Cells flattened, ovate; wall with crossed spirals P. pyrum (Fig. lg)

Cells conically rounded at anterior end (tapered and twisted below); walls with crossed spirals p- tortus (Fig. le, f)

3. Cells heart-shaped, broadly rounded at anterior end; tail oblique... P. pleuronectes Cells ellipsoid or ovoid, broadly rounded at posterior end; tail straight

P. acuminatus (var. drezepolskii)

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Trachelomonas

1. Cells elliptical; walls finely granular T. granulosa Cells spherical to elliptical; walls smooth or spiny 2

2. Cell wall smooth, orange; collar absent T. volvocina (Fig. lh) Cell wall spiny, reddish-brown; collar present T. sydneyensis (Fig. Id)

C R Y P T O P H Y C E A E

1. Cells up to 20 jim long, pear-shaped, vivid blue-green; gullet absent Chroomonas (C. nordstedtii) (Fig. 2j)

Cells up to 30 jim long, slipper-shaped, reddish-brown; gullet present Cryptomonas (C. erosa) (Fig. 2h)

E U C H L O R O P H Y C E A E

1. Cells single 2 Cells in colonies 17

2. Cells with 2 equal flagella 3 Cells with 4 equal flagella Carteria (C. globosa)

3. Cells spherical or oval Chlamydomonas Cells elongate 4

4. Cells, narrowly spindle-shaped Chlorogonium Cells with a winged envelope 5

5. Cells, flattened (hexagonal in side view) Pteromonas (P. angulosa var. vexilliformis) (Fig. 2d, e)

Cells not motile, not flattened 6 6. Cells mucilage-coated Elakatothrix (E. gelatinosa)

Cells not mucilage-coated 7 7. Cells with 2 straight spines Diacanthos (D. belenophorus)

Cells without 2 straight spines 8 8. Cells single (needle-shaped) 9

Cells in bundles Ankistrodesmus (Fig. 3h) 9. Cells slightly curved Monoraphidium (= Selenastrum)

Cells straight or curved 10 10. Cells, long, usually curved, (pointed, in two halves; rows of starch bodies

(pyrenoids) in each chloroplast) Closterium Cells not curved 11

11. Cells with 2-16 polar and equatorial spines (spherical or oval) Chodatella (= Lagerheimia - C. subsalsa)

Cells without polar and equatorial spines 12 12. Cells angular with 4 or 5 angles Tetraedron (T. muticum)

Cells with rounded corners 13 13. Cells with clusters of bristles at corners

Polyedriopsis (P. spinulosa) (Fig. 3i) Cells elongated 14

14. Cells with branched spines Schroederia (S. setigera) Cells without branched spines 15

15. Cells long, pointed (with one chloroplast) Closteriopsis (C. longissima) Cells spherical 16

16. Cells with long spines (projecting like knitting needles).... Golenkinia (G. radiata) Cells oval, without spines Oocystis (O. marssonii)

17. Cells in rectangular colonies, motile Gonium (G. pectorale) Cells not in rectangular colonies 18

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18. Cells in spherical colonies (motile) Pandorina (P. morum) Cells in oval colonies 19

19. Cells in asymmetrical colonies Uva(= Pyrobotrys - U. gracilis) Cells in spherical colonies 20

20. Colonies motile Sorastrum (S. spinulosum) Colonies not motile 21

21. Cells mostly lying in one plane (in flat plates) 22 Cells lying in more than one plane 26

22. Cells elongated, parallel (in 2's, 4's or 8's), with strong spines at corners Scenedesmus

Cells not elongated, not parallel, without spines at corners 23 23. Cells with processes, in flat plates (radially arranged) Pediastrum

Cells not in flat plates 24 24. 4 cells, in 2 planes Tetrallantos (T. lagerheimii)

More than 4 cells, in filaments 25 25. Many brick-like cells, in filaments Schizomeris (S. leibleinii) (Fig. 4f)

Cells not in filaments 26, 27 26. Cells in tightly packed balls Coelastrum (C. microporum)

Cells loosely linked by forked strands of mucilage Dictyosphaerium (D. ehrenbergianum)

27. Cells spherical, in squares or triangles, with many long delicate spines Micractinium (probably including single-celled Chlorella (Fig. 3a)

Cells elongated, in star-shaped colonies Actinastrum (A. hantzschii) (Fig. 3g)

Chlamydomonas

1. Cells 10-15 Jim long; (beaked); chloroplast cup-shaped 2 Cells 18-21 um long (narrowly ovoid); chloroplast covering most of cell wall

C. snowiae 2. Cells almost spherical (pyrenoid conspicuous) C. cingulata (Fig. 2a)

Cells almost cylindrical (flagella longer than body) C. bacillus (Fig. 2b)

Chlorogonium

1. Cells up to 20 jim long, (elongated, pointed at base), wide (C. leiostracum) (Fig. 2c - after Haughey 1969)

Cells (pointed at base), narrow 2 2. Cells up to 45 um long, extended at flagellar end C. elongatum

Cells up to 30 um long, pointed at both ends C. aculeatum

Closterium

1. Cells slender, about 100 times as long as wide, up to 580 Jim long C. aciculare Cells shorter 2

2. Cells robust, nearly straight, up to 460 Jim long, chloroplast ridged, with 7-11 pyrenoids in a single row C. acerosum Cells slender, slightly curved, up to 380 Jim long, with 3-4 pyrenoids in a single row

C. cornu (Fig. 3d)

Micractinium

1. Cells spherical, in pyramids or squares, with spines up to 35 Jim long. M. pusillum Cells in 4's, ovate, arranged about a central space, spines up to 40Jim long

M. quadrisetum (Fig. 3b)

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Monoraphidium

1. Cells long, straight, with spine-like ends M. setiforme (Fig. 2f) Cells twisted or curved; ends rounded or pointed but not spine-like 2

2. Cells slightly curved, long, fine; chloroplasts blue-green M. tortile Cells strongly curved 3

3. Cells twisted more than once M. contortum (Fig. 2g) Cells with only one twist 4

4. Cells slightly twisted, pointed at ends; (chloroplast bluish) M. irregulare Cells cylindrical, curved, with rounded ends; (chloroplast incised on inner side)

(M. minutum (= Selenastrum minutum)

Pediastrum

1. Outer cell walls granular, 5-6 sided, with 1-2 stump-like projections... P. integrum Outer cell walls with 2 projections 2

2. Colony perforate; outer cell projections long and tapering P. duplex Colony entire; outer cell projections short, blunt P. boryanum

Scenedesmus 1. Outer cells with long curved spines at ends 2

Outer cells with or without short spines 3 2. Cells rounded at ends, completely joined lengthwise S. quadricauda (Fig. 4c)

Cells narrowed at ends, partly joined lengthwise at different angles S. opoliensis (Fig. 4d)

3. Cells strongly bowed, not in one plane S. acuminatus (Fig. 4b) Cells not bowed, usually in one plane 4

4. Cells up to 8 um long, ovate, (incompletely joined lengthwise) S. intermedius (Fig. 4a)

Cells up to 21 p long, squat, (irregularly slanted) S. pannonicus (Fig. 4e)

C H R Y S O P H Y C E A E

1. Cells amoeboid; plastids yellow-brown, single 2 Cells firm; plastids yellow-brown, in colonies Synura (S. uvella)

2. Cells free, in surface films, with radiating projections Rhizochrysis Cells solitary, urn-shaped with a large open pore Kephyrion

D I A T O M O P H Y C E A E

1. Cells like petri dishes 2 Cells like oblong boxes 3

2. Ends (valves) with radial markings, without marginal spines Cyclotella (C. meneghiniana)

Ends (valves) with radial markings and rings of marginal spines Thalassiosira (T. hasleae)

3. Ends (valves) oval-cylindrical, with two parallel plastids and two lines parallel to margins Caloneis (C. bacillum) Ends (valves) boat-shaped 4, 5

4. Ends (valves), symmetrical; slit (raphe) in two diagonally opposite angles of cel l . . . Nitzschia

Ends (valves), asymmetrical; slit (raphe) in 2 adjacent angles of cell Hantzschia (H. amphioxys)

5. Ends (valves) bilaterally symmetrical, usually narrower at one end Gomphonema (G. parvulum) (Fig. 3c)

Ends (valves) asymmetrical; one end hemispherical Cymbella (C. affinis)

Nitzschia

Valves large, up to 300 um long, broadly elliptical; (central longitudinal fold) N. circumsuta

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Fig. 1. (a) Euglena acus; (b) Euglena gracilis; (c) Euglena haematodes; (d) Trachelomonas sydneyensis; (e) Phacus tortus; (f) Phacus tortus; (g) Phacus pyrum; (h) Trachelomonas volvocina. Bar = 10 um.

126

Fig. 2. (a) Chlamydomonas cingulata; (b) Chlamydomonas bacillus; (c) Chlorogonium leiostracum; (d) Pteromonas angulosa var. vexilliformis; (e) Pteromonas angulosa var. vexilliformis; (f) Monoraphidium setiforme; (g) Monoraphidium contortum; (h) Cryptomonas erosa; (i) Anabaenopsis circularis; (j ) Chroomonas nordstedtii Bar = 10um.

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Valves small, up to 60 Jim long, narrow, straight N. palea (Fig. 3f)

C Y A N O P H Y C E A E

1. Cells minute, in colonies 2 Cells larger, in filaments or plates 3

2. Cells blackish, in spheres or loosely arranged clusters Microcystis Cells pale blue-green, in small flat plates Merismopedia

3. Filaments gliding, straight or curved, cells cylindrical; spores absent. Oscillatoria Filaments not gliding, spirally curved, cells barrel-shaped, thick-walled spores (heterocysts) at both ends Anabaenopsis circularis (Fig. 2i)

Oscillatoria

Filaments straight, up to 5. 6/im wide O. tenuis Filaments straight or curved, up to 6. 0 jam wide

O. (Spirulina - Arthrospira) platens is (Fig. 3e) A C K N O W L E D G E M E N T S

I thank the following for assistance with collecting samples: Mrs Kathleen Cooper and Dr Dinah Brockett (North Shore Drainage Board Purification Works, Albany) and Mrs Deirdre Oliver (Auckland Regional Authority, Manukau Purification Works, Mangere). Mr Arthur Haughey (A. R. A . , Manukau Purification Works) kindly gave permission for the inclusion of his records in the keys. I am indebted to Drs Elizabeth Edgar and M . J . Parsons for helpful criticism of the text.

R E F E R E N C E S

Belcher, H . & Swale, E . 1976: " A Beginner's Guide to Freshwater Algae. " London. Her Majesty's Stationery Office. 47 p.

Belcher, H . & Swale, E . 1979: " A n Illustrated Guide to River Phytoplankton". Her Majesty's Stationery Office. 64 p.

Brockett, D. 1973: The mechanism of breakdown of N compounds in oxidation ponds. Proceedings of the Pollution Research Conference. New Zealand Department of Scientific and Industrial Research Information Series 97: 89-102.

Cassie, V . 1979: Algae in relation to water quality. 21-30. In: Mulcock P. A . (Ed), A review of some biological methods for the assessment of water quality with special reference to New Zealand. National Water and Soil Technical Publication 18: 1-46.

Haughey, A . 1968: The planktonic algae of Auckland sewage treatment ponds. New Zealand Journal of Marine and Freshwater Research 2: 721-766.

Haughey, A . 1969: Further planktonic algae of Auckland sewage treatment ponds and other waters. New Zealand Journal of Marine and Freshwater Research 3: 245-261.

Haughey, A . 1970: Notes on Euglena acus Ehrenberg from sewage treatment ponds. British Phycological Journal 5: 97-102.

Hutchinson, E . G. & Oliver, D. A . 1978: A survey of oxidation ponds in the Auckland region. Auckland Regional Authority Works Division Report, 114 p.

Palmer, C M . 1980: "Algae and Water Pollution. " England. Castle House Publications. 123 p.

Prescott, G . W. 1962: "Algae of the Western Great Lakes Area" . Brown, Iowa. 977 p. Rowe, D. 1975: Phytoplankton populations and physico-chemical variables in a sewage

treatment pond. M . Sc thesis, University of Auckland. 158 p. Vincent, W. F. & Silvester, W. G. 1979a: Growth of blue-green algae in the Manukau (New

Zealand) oxidation ponds. 1. Growth potential of oxidation pond water and comparative optima for blue-green and green algal growths. Water Research 13: 711-716.

Vincent, W. F. & Silvester, W. G. 1979b: Growth of blue-green algae in the Manukau (New Zealand oxidation ponds. II. Experimental studies on algal interaction. Water Research 13: 717-723.

Whitford, L. A . & Schumacher, G. J . 1973. " A Manual of Freshwater Algae. " Raleigh, Sparks. 324 p.

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Appendix I. Pigmented algae identified from oxidation ponds near Auckland, 1977—1981. Scale of abundance: 5 4 3 2 1

= very abundant or dominant = abundant = common = occasional = scarce

o O

r = one specimen seen E U G L E N O I D F L A G E L L A T E S -E U G L E N O P H Y C E A E Euglena acus Ehrenberg (Fig. Ia) Euglena geniculata Dujardin Euglena gracilis Klebs (Fig. Ib) Euglena minuta Prescott Euglena haematodes (Ehrenberg) Lemmermann

(Fig. lc) Euglena Spirogyra Ehrenberg Phacus pleuronectes (O. Mueller) Dujardin Phacus pyrum (Ehrenberg) Stein (Fig. lg) Phacus tortus (Lemmermann) Skvortzow (Fig. le, f) Lepocinclis texta (Dujardin) Lemmermann Trachelomonas granulosa Playfair Trachelomonas sydneyensis Play fair (Fig. Id) Trachelomonas volvocina Ehrenberg (Fig. lh) Trechelomonas sp. (clean wall)

C R Y P T O P H Y T E S - C R Y P T O P H Y C E A E Chroomonas nordstedtii Hansgirg (Fig. 2j) Cryptomonas erosa Ehrenberg (Fig. 2h)

G R E E N A L G A E - E U C H L O R O P H Y C E A E Actinastrum hantzschii Lagerheim (Fig. 3g) Actinastrum hantzschii var. fluviatile Schroeder Ankistrodesmus falcatus (Corda) Ralfs (Fig. 3h) Chlamydomonas bacillus Pascher et Jahn (Fig. 2b) Chlamydomonas cingulata Pascher (Fig. 2a) Chlamydomonas sp. (1 pyrenoid) Chlamydomonas sp. (2 pyrenoids) Chlorella minutissima Fott et Novakova Chlorella vulgaris Beijerinck (Fig. 3a) Chlorogonium leiostracum Strehlow (Fig. 2c) Closterium cornu Ehrenberg (Fig. 3d) Closterium jenneri Ralfs Coelastrum microporum Naegeli Dicanthos belenophorus Korschikov Dictyosphaerium ehrenbergianum Naegeli Elakatothrix gelatinosa Wille Golenkinia radiata Chodat Micractinium pusillum Fresenius Micractinium quadrisetum (Lemmermann)

G. M . Smith (Fig. 3b) Monoraphidium contortum (Thuret) Fott et

Legnerova" (Fig. 2g) Monoraphidium minutum (Naegeli) Fott et Legnerova Monoraphidium setiforme (Nygaard) Fott et

Legnerova (Fig. 2f)

¥ ta

C

5 5

1 2

5 1 1 .

1 1 1 .

1 -a

1 3

r 5 5

129

Fig. 3. (a) Chlorella vulgaris; (b) Micractinium quadrisetum; (c) Gomphonema parvulum; (d) Closterium cornu; (e) Oscillatoria platensis; (f) Nitzschia palea; (g) Actinastrum hantzschii; (h) Ankistrodesmus falcatus; (i) Polyedriopsis spinulosa. Bar = 10jim.

130

Fig. 4. (a) Scenedesmus intermedius; (b) Scenedesmus acuminatus; (c) Scenedesmus quadricauda; (d) Scenedesmus opoliensis; (e) Scenedesmus pannonicus; (f) Schizomeris leibleinii. Bar = 10 um.

131

O w K <

o O be

«

o O

3 •

Monoraphidium tortile (W. et G. S. West) Fott et Legnerova

Monoraphidium irregulare (G. M . Smith) Fott et Legnerova

Oocystis marssonii Lemmermann Pandorina morum (Mueller) Bory Pediastrum boryanum (Turpin) Meneghini Pediastrum duplex var. gracillium W. et G. S. West Polyedriopsis spinulosa Schmidle (Fig. 3i) Pteromonas angulosa var. vexilliformis Playfair

(Fig. 2d, e) Scenedesmus acuminatus Playfair (Fig. 4b) Scenedesmus intermedius Chodat (Fig. 4a) Scenedesmus opoliensis P. Richter (Fig. 4d) Scenedesmus pannonicus Hortobagyi (Fig. 4e) Scenedesmus quadricauda (Turpin) Brebisson (Fig. 4c) Schizomeris leibleinii Kuetzing (Fig. 4f) Tetraedron muticum (A. Braun) Hansgirg

Y E L L O W - B R O W N A L G A E - C H R Y S O P H Y C E A E Rhizochrysis sp. Kephyrion sp. Synura uvella Ehrenberg D I A T O M S - D I A T O M O P H Y C E A E Caloneis bacillum Grunow) Cleve Cyclotella meneghiniana Kuetzing 5 Cymbella affinis Kuetzing Gomphonema parvulum (Kuetzing) Kuetzing (Fig. 3c) 1 Hantzschia amphioxys (Ehrenberg) Grunow Nitzschia circumsuta (Bailey) Grunow Nitzschia palea (Kuetzing) W. Smith (Fig. 3f) Thalassiosira hasleae Cassie et Dempsey

3 1

3 1 2

1 2 1

. 3 2

. 3 2

. 3 .

2 3 2 . . 5 . 3 . 1

. 1 1 1

r 1 . 1

1 5 1 5 5 . 5 5

B L U E - G R E E N A L G A E - C Y A N O P H Y C E A E Microcystis aeruginosa Kuetzing 5 3 5 + . 5 + Merismophedia glauca (Ehrenberg) Naegeli Oscillatoria tenuis Agardh Oscillatoria (subgenus Spirulina) platensis (Nordstedt)

Bourrelly (Fig. 3e) 3 . 2 Anabaenopsis circularis (G. S. West) Woloszynska et

Miller (Fig. 2i) . 5 + .

4 5 3 5 1 4

132