Algae ~ Some common freshwater types with links to Micscape resources

Algae are a very diverse group of organisms that vary widely in size, shape, colour and habit. Ten or so phyla are represented in freshwater. This page gives an overview of some commonly found freshwater algae.

The algae have been grouped by their major features. Some of these are artificial groups (i.e. not necessarily related to their taxonomy) but are convenient ones for the pond dipper. More about the classification of algae and protozoa.



Key features 

Micscape links

Flagellated forms (some are also often classed as protozoa)
note: These flagella are hardly visible, only with strong magnification.



green, flagella (whip-like cilia), free-swimming, red eye spot, body is flexible <0.4 mm

Flagellated algae/protozoa - includes Euglenaa heart shaped euglenoid: Phacus


brown, 2 flagella, (1 in girdle), free-swimming, tough armour <0.4 mm

Peridinium - Stars of the Marshes

Green algae

spherical colonies, cells with 2 flagella
Volvox: 0.5 - 2mm

Volvox - the jewel of the pond
Volvox in 3D
Some other smaller colonial flagellates: Gonium, Eudorina, Pandorina, Sorastrum (rare), Synura, Uroglena

not all green algae are green

tiny, green/red, often in bird baths
<0.05 mm

Haematococcus - image
another small flagellated green algae: Chlamydomonas

There are many other small flagellated algae of non related groups. Classification is difficult.

Non-flagellated forms


Blue-green algae (cyanobacteria)

blue-green, often slow locomotion,
used to be considered algae but more related to bacteria cells<0.05 mm colonies can be many mm

Smallest page on the web - 'bacteria' - image of a cyanobacteria


usually brownish, silica cell wall in two parts, solitary or colonial, some have a slow gliding motion
<0.5 mm

Smallest page on the web - 'diatoms'
Those who live in glass houses'
Diatoms on strings
Bacillaria - 'Carpenter's rule' diatom
Library search - type diatom for articles on f/water & marine species
Test diatoms - species to test optics

(Gamophyta: conjugating green algae)

green, no flagella, mainly solitary, some colonial, various shapes, two semi-cells which are mirror images
<0.5 mm

What are desmids?
Smallest page on the web - desmids
Bill Ells' page - extensive articles on various species and aspects of desmids
Desmids in 3D
Desmid gallery

Green algae

green, don't move, no flagella, not attached to a surface

starshaped colony: Pediastrum <0.3 mm
bottom right: Scenedesmus <0.03 mm

Pediastrum - image only
Pediastrum - the 'star' of the pond

Some other common 'non flagellates': Chlorella (symbiont in several organisms), Scenedesmus, Dictyosphaerium

Other algae of various growth forms


Water net

a sock-like colony, green algae (related to Pediastrum) up to 20 centimeters

Hydrodictyon - the water net

Some other common algae of various types: Botrydium, Chaetophora, Coelochaete, Enteromorpha

Filamentous forms


Pond scum
(Gamophyta: conjugating green algae)

non-branching, green, chains of cells with distinctly shaped cell contents
cell with <0.1 mm. length: centimeters

Spirogyra - chloroplasts like helix
Spirogyra in 3D
Zygnema - starshaped chloroplasts
Mougeotia has plate-like chloroplasts

Other non-branching forms

several non related groups

Some other common filamentous types: Tribonema, Ulothrix, Vaucheria

Branching forms

mostly green algae

Cladophora, Draparnaldia, Stigeoclonium

Red algae (Rhodophyta)

mainly marine, but some freshwater forms, not always red




First Page



Collecting tips

Insect stages 


Some introductory books on freshwater algae:

From the Pictured Key Nature series: 'How to know the freshwater algae' by G.W. Prescott.
Wm. C. Brown Company Publishers, Dubuque, Iowa
in this series also avaliable: 'How to know the Protozoa' by Jahn, Bovee and Jahn

'A beginner's guide to freshwater algae' by H Belcher and E Swale. Institute of Terrestial Ecology, 1978.

Note: This page with links hopefully gives a useful overview, but it's neither a formal identification guide nor comprehensive. Stoneworts for example, which are macroscopic algae looking like a higher plant, have not been included (but would welcome articles).

Many thanks to all the Micscape contributors whose articles this guide links to. For clarity their names are omitted in the links above. Articles and/or images on any of the groups without links (e.g. protozoa in black type) would be welcome.

Some of the artificial groups and key features have been adapted from those in 'Collins field guide to freshwater life' by R Fitter and R Manuel, 1986. Any mistakes are by the web page authors!

An Introduction to Microscopy

Comments to the compilers Wim van Egmond and Dave Walker are welcomed.

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