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INTRODUCTION

This key deals with algae and phytoplankton which are fairly commonly distributed throughout the Auckland province and as far as the lakes of Taupo and Rotorua. Fresh-water algae may be found in practically any source of fresh water, including lakes, pools, inland streams, stagnant pools and even the city water supply. Since it is possible to discuss only a limited number of algae here, several references will be given as a guide to further studies.

When identifying algae, it is useful to refer to a key, and in order to use this efficiently, some knowledge of the terms in common usage i s an advantage (see glossary). Familiarity with the descriptive terms is only gained after some experience. The primary difficulty l ies in detecting differences between the various pigmentations which are, of course, important in identification.

METHODS OF COLLECTING For the elementary student, the only necessary equipment is a knife

or similar instrument and several small glass jars or bottles with labels. The organisms can be collected from moist rocks or trees, fish tanks or any glass containers which have been used for flowers and left for a few days, as well as ponds, lakes and streams. They also exist in extremes of temperature and humidity, growing as well in hot springs as in snow fields at high altitudes. Many algae dry out when conditions demand it, lie dormant and are either carried by air to new localit ies or remain until moist conditions permit new growth. When collecting, try to keep a record of the area and source of the plant. It i s desirable, in some c a s e s , as with motile ce l l s , to kill and preserve the plant in a solution of 6 parts water, 3 parts alcohol and 1 part formalin. This mixture tends to retain the original cell structure and simplifies the identification of motile algae. Access to a microscope of reasonable quality, say up to a 40X objective lens, i s necessary, and a set of clean glass s l ides with cover s l ips . When mounting algae, mount sparsely; that is to say avoid putting a clump on the slide as it i s very difficult to determine structure under these conditions.

ALGAL COUNTS One simple method of estimating the number of phytoplankton per unit

volume is the haemocytometer sl ide. An elementary type is an improved Nebauer, marked in l / 400 th of squ. mm. and .1 mm in depth. Counts may be made with the use of a Student Olympus monocular microscope at 100X power. For the microscopic unicellular species , this particular microscope is inadequate as identification relies largely on the ability of the observer to distinguish the difference between both chloroplast and flagella struc-tures. The number of organisms in the field are counted several times, depending on the consistency of the counts, and then averaged and brought to a unit volume of 1 ml. Most of the counts from which information for this article was taken were recorded from samples taken from the lakes at either Rotorua or Taupo.

T A N E ( 1 9 6 6 ) 12 : 5 - 1 1

FRESH WATER ALGAE

by Helen Cameron

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SUMMARY OF GENERA

1. Plant. 2. Structure. (U) unicellular, (F) filamentous, (C) colonial,

(M) motile, (O) others. 3. Colour or group. (D) diatom, (G) green, (BG) blue-green, (R) red,

(F l ) flagellate, (De) desmid, (YG) yellow-green.

1. 2. 3. Anabaena F BG Ankistrodesmus O G Asterionella O D Chlamydomonas M,U G.Fl Chlorella U G Closterium O De Coelastrum C G Cosmarium O De Cyclotella O D Diatoma U D Dinobryon C F l Draparnaldia O G Eudorina C G.Fl Euglena M.U G.Fl Fragilaria O D Gomphonema O D Gonium C G.Fl Haematococcus M,U G.Fl Hyalotheca O De Hydrodictyon O G Melosira F G Microspora F G Mougeotia F G Navicula O D Oscillatoria F BG Pandorina C G.Fl Pediastrum O G Scenedesmus C G Selenastrum C G Straurastrum O De Synedra C D Tabellaria O D Ulothrix F G Vaucheria F YG Volvox C G.Fl

KEY TO THE GENERA *

1. Cells with chloroplasts. (2) 1. Cells without chloroplasts, but diffused pigments. DIATOMS.

Cells solitary, colonial or filamentous, walls si l iceous and etched in definite patterns. Walls in two sections, movement gliding or jerky.

(25) * E D I T O R S N O T E : F o r i l l u s t r a t i o n o f m o s t o f t h e s e g e n e r a s e e t h e f o l l o w i n g a r t i c l e .

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2. Plant with definite green pigment, positive iodine reaction.(3) 2. Plant yellow green, blue green, negative iodine reaction. (22)

3. Plant motile, (4) 3. Plant non-motile. (9)

4. Motile cel ls solitary. (5) 4. Motile ce l l s colonial. (6)

5. Protoplast narrow at anterior end. Protoplast narrower at anterior end and the same shape as the envelope, or ce l l s without envelopes. CHLAMYDOMONAS.

5. Protoplast separate from cell wall. Protoplast separated from cell wall by mucilaginous channel and connected by fine radiating processes. Cells with haematochrome masking green pigment. HAEMATOCOCCUS

6. Colony spheroid or ovoid. (7) 6. Colony circular or sub-quadrangular plate.

Colony a plate of 4 - 1 6 ce l l s , somewhat pyriform, moving with a tumbling motion. GONIUM.

7. Colony l e s s than 500 ce l l s . (8) 7. Colony more than 500 ce l l s .

Colony of 100's of ce l l s arranged in globular form. VOLVOX. 8. Colony with cel ls arranged centrally, in sphere or oval.

PANDORINA. 8. Colonial ce l l s all the same s ize , ovoid, and arranged in tiers.

EUDORINA. 9. Cells separate but clustered or colonial. (10) 9. Cells arranged in filaments. (18)

10. Cells clustered (11) 10. Cells colonial. (15)

11. Cells needle-like or sickle-shaped. (12) 11. Cells ovoid, elongate or pyramidal. (13)

12. Cells needle-like or sickle shaped, clustered but separate, regularly curved in groups of 4 - 3 2 , convex walls approximated no envelope. SELENASTRUM.

12. Cells straighter, needly like or slightly curved, sometimes solitary rather than clustered, loosely entwined, fusiform. ANKISTRODESMUS.

13. Cells elongate. Cells with axial chloroplasts, one in each horn of cel l , Cells elongate, slightly curved and divided in the mid region. Nucleus central, polar vacuoles. CLOSTERIUM.

13. Cells oval circular, pyrimidal or star-shaped, isodiametrically angular, up to 3X diameter in length. (14).

14. Cells star-shaped, or triangular when seen from above, due to extensions from apices on three planes . STRAURASTRUM.

14. Cells without extensions at apices, semicel ls compressed or

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rounded from top view, margin of cell spineless , 1 chloroplast in semicell . COSMARIUM.

15. Colony a plate of sac . (16). 15. Colony a row or sphere. (17)

16. Cells attached by side or end walls to form regular arrangement. Cells cylindrical in shape, attached one to two others at end walls to form a net in plate or sac arrangement.

HYDRODICTYON. 16. Cells irregular shapes, arranged in circular or irregular plates,

with external ce l l s sometimes varying in shape from internal ones. Cells arranged in multiples of 2 from 4 - 6 4 . PEDIASTRUM.

17. Cells roughly ovoid and arranged in colonies of 1 or 2 rows. Spines poles of ce l l s . Normally ce l ls occur in 4's, sometimes 2's, with long axes parallel. SCENEDESMUS.

17. Cells spherical or polygonal in hollow colonies, joined by mucilagin-ous threads. Protuberances occasionally at the ends of the threads . COELASTRUM.

18. Plant filamentous, microscopic and unbranched, freefloating.(19) 18. Filaments branched.

Main axis composed of barrel shaped ce l l s , roughly all the same s ize , with tufted, branched plumes arising from it. Plant pale green and enclosed in a watery mucilage. DRAPARNALDIA.

19. Cells containing a band-like chloroplast. (20) 19. Cells without a band-like chloroplast. (21)

20. Cells longer than wide with one band-like chloroplast. MOUGEOTIA.

20. Cells approximately as long as wide, chloroplast band-like, may partially or completely encircle the cel l . ULOTHRIX.

21. Cells cylindrical, square to rectangular, with emarginations rather than incisions at mid region. A filamentous desmid. HYALOTHECA.

21. Cells without haematochrome, chloroplast a perforated or padded sheet or a branched beaded ribbon. Walls tend to show H-shaped pieces at divisions. Cells uninucleate. MICROSPORA.

22. Plants yellow green. (23) 22. Plants blue green. (24)

23. Filaments not branched, without constrictions. Plant yellow green to dark green, or brown at maturity. May be fresh or salt water. VAUCHERIA.

23. Plant colonial, chloroplasts motile, enclosed in branching loricas. Envelopes colourless, arising 2 from 1 to cause branching. DINOBRYON.

24. Plant a thread like filament, (trichome) with a sheath, composed of many bead like cel ls heterocysts present in trichome. May

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be solitary threads, or massed. Trichomes covered with a soft mucilage. ANABAENA.

24. Trichomes without a sheath, unbranched, oscillating, some straight and rigid, some curved. Many celled trichomes solitary or intermingled with other algae and each other, tapering slightly, swollen apex. OSCILLATORIA.

25. Long rod or boat shaped frustules, some rectangular or wedge. 2X as long as wide. (26)

25. Frustules isodiametrical, round, rectangular or oval, l e s s than 2X diameter in length. Circular valve with costae inside margin and smooth to finely punctate walls in central area. Cells arranged parallel to form chains. CYCLOTELLA.

26. Frustules usually solitary. (27) 26. Frustules aggregated. (28)

27. Frustules symmetrical, elliptic, or sub-elliptic, often poles subcap-itate.

Rectangular girdle view, valve view oval or elongate. Cells mostly solitary or joined to form chains. DIATOMA.

27. Frustules narrow or linear, transversely ornamented. 2 -8 chromato-phores. NAVICULA.

28. Frustules attached to gelatinous stalks. (29) 28. Frustules in chains, ribbons or filamentous. (30)

29. Cells long and narrow, needle like, may have slightly swollen poles, solitary or colonial, attached to substrate by gelatinous stalk. Frustules longer than wide, epiphytic. SYNEDRA.

29. Cells assy metrical, wedge shaped, and slightly larger at one end. Usually attached to branched gelatinous stalks by narrow end. GOMPHONEMA.

30. Frustules in chains or ribbons. (31) 30. Frustules filamentous or otherwise. (32)

31. Frustules with longitudinal septa, not showing costae, arranged in zigzag chains, cel ls attached at corners, poles slightly capitate. TABELLARIA.

31. Valve view poles narrower, centrally enlarged. Girdle view quadrate or rectangular, in ribbon arrangement. Free floating or s e s s i l e colonies. FRAGILARIA.

32. Filamentous, cylindrical capsule like ce l l s , may have gesticulations between them. MELOSIRA.

32. Frustules long or rectangular, radiating from centre in wheel like arrangement. Slightly enlarged at poles. Two pores at central poles exuding mucilage connecting cel ls together. ASTERIONELLA.

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GLOSSARY OF TERMS

acicular anterior apex apical axial

bloom

bristle capitate chlorophyll chloroplast

chromatophore

colonial mucilage conjugation

constricted contractile vacuole crescent

cup-shaped cyst ellipsoid

epiphyte euplankton filament flagellum

girdle view gregarious

haematochrome

hard water Heterocyst

hold fast cell H- shaped sections

incised isodiametrical Kelp lorica

needle like, forward end. summit, terminus, end of projection, top most. along the centre line bisecting an object either transversely or longitudinally, profuse growth of planktonic algae, forming scums which cloud or colour the water. stiff hair, enlarged pole. green photosynthetic pigment. varied shaped body inside cel l wall, containing green pigment. body within cell , not containing chlorophyll but some other pigment. gelatinous envelope enclosing many ce l l s , sexual reproduction by gametes moving across a join of 2 ce l l s . indented as at joints between ce l l s of filament, small cavity in cell , bounded by pulsating membrane, arc shaped or curved cell , cylindrical in the middle and tapered at each end. complete body within cell , open at one end as a cup. thick walled quiescent cell , dormant stage, plane figure with curved margines, poles sharply rounded. living upon another plant. open water, floating plankton. thread of ce l l s or 1 or more rows of ce l l s . organ of locomotion of unicels or zoospores, whiplike. seen from the side. habit of some genera to group together without actually being attached. red or orange pigment which masks chlorophyll in some green algae. well supplied with minerals pH P> 7.0. enlarged cell occurring in, for example Anabaena, different in shape from the others, basal cell acting as an attaching organ, segments of filaments resulting from ce l l s separating at mid region. cut in. all planes appearing to have the same diameter, common name for large brown seaweeds, shell like structure housing motile organism.

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lunate multinucleate nodule parietal

perforate plankton

plate pole polygonal posterior process protoplast punctate pyrenoid pyriform quadrate radiate reticulate semi cell

sheath thallus tychoplankton valve vegetative

Palmer, 1962

Prescott, G.W. 1962

Prescott, G.W. 1964

crescent shape, having many nuclei, small swelling. along the wall — along the edge as opposed to the middle. with pores. organisms which tend to drift with currents — motile or non motile. flat, polygenal arrangement of ce l l s , the ends of a cell or ce l l s , many sided, rear. extension of cell, protrusion. living part of cell, cytoplasm. small pores, holes or pits in a cell wall. starch covered protein body, usually in chloroplast. pear shaped. 4 sided. extending outward in several planes, netted. cell — half — as in dismids both parts mirror image of each other. mucilaginous covering of cell colony, envelope, algal plant body. plankton near the shore, entangled in other plants, top or bottom view of diatom, non reproductive stage of plant.

REFERENCES

"Algae in Water Supplies". U.S. Dept of Health.

"Algae of the Western Great Lakes Area". Brown Co. Iowa.

"How to know the Fresh Water Algae", Brown Co. Iowa.