What Are 'Algae'?

Classification System

Where Do 'Freshwater Algae' Grow?

How Do I Collect, Preserve & Observe Freshwater Algae?

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Freshwater
Algae

Algae grow in almost every habitat in every part of the world. The following are examples of non-marine (loosely termed 'freshwater' here) habitats.

Animals: Reported substrates include turtles, snails, rotifers, worms, crustacea and many other animals (e.g. alligators and three-toed sloths are hosts outside Australia). Anabaena grows inside the aquatic fern Azolla, Nostoc within members of the Anthocerotales. Freshwater sponges and some other animals (e.g. infusoria, rhizopods) have symbiotic relationships with algae.

Aquatic plants: Algae grow on and inside water plants (including other algae), but are generally not restricted to a single host.

‘Artificial’ substrates: Wooden posts and fences, cans and bottles etc. all provide algal habitats.

Billabongs & lagoons: Rich microalgal habitats, particularly for desmids. Their ecology is poorly understood and changes in flooding regime may alter the algal flora.

Bogs, marshes & swamps: Rich desmid habitats (e.g. in Sphagnum).

Farm Dams: These ‘artificial’ water-bodies may allow taxa to extend their 'natural' range.

Hot springs: Little is known of hot springs algae in Australia, but as elsewhere the blue-green algae (Cyanobacteria) dominate except where sulfide concentrations are high.

Lakes: Coloured (or humic) lakes are usually species-rich but are uncommon in most of Australia. All lakes have a floating (or swimming) microalgal flora and an ‘attached’ micro- and macro-algal flora.

Mud and sand: The surface of submerged soil in shallow waters supports many species.

Ponds (ephemeral), puddles, roadside ditches and rock pools: Little studied in Australia.

Reservoirs: Well-established reservoirs with protected catchments provide ideal habitat for many microalgae, particularly desmids. So-called 'protected' catchments have world-wide value given the paucity of such systems overseas.

Rivers: Very few lowland rivers are in a pristine state; an understudied habitat.

Rock (internal): e.g. Australian Antarctic Territory where some algae live within rocks.

Rock (surface): Little studied in Australia.

Saline & Hypersaline Lagoons: These mostly coastal habitats have an intriguing microalgal flora but are very sensitive to changes in the water table.

Saline Lakes & Marshes: e.g. Basalt Plains of Victoria. Species poor but with distinctive algal flora.

Salt marshes and salt lakes: Again not a strictly 'fresh' water habitat, but a distinctive non-marine one. On mud around and in salt lakes and saline channels, Vaucheria is usually common, at least in the wetter months. Enteromorpha and Rhizoclonium also grow in brackish to saline waters.

Snow: 'Red snow' is usually coloured by Chlamydomonas, but other algae occur in this habitat.

Soil: e.g. cryptogam mats in dry country. Species composition largely unknown, but of great environmental importance. Anabaena grows in nodules formed on the surface roots of cycads.

Streams: Acidic streams support a diverse macroalgal flora and are highly susceptible to impaction, eutrophication and river engineering. Alkaline streams are not common naturally in Australia. They seem to be species poor, but due to restricted occurrence they may support rare taxa. Eutrophic streams are species poor, but sometimes native taxa remain and, due to shortage of oligotrophic streams in some areas, they may represent the last fragments of a previously wide distribution.

Terrestrial plants: Trentepohlia and related species have a very similar habit to lichenised fungi, growing on tree trunks and branches. Apatococcus (previously included in the more broadly circumscribed Protococcus) is universally common as a green powdery covering on the shady side of trees. A variety of blue-green algae readily colonize damp walls and other moist surfaces. Algae also live on the surface of, or penetrate into, leaves; it is possible that such species are extremely diverse in rainforests. Lichens, a symbiosis between algae and fungi, usually contain green algae (particularly Trebouxia and less commonly Trentepohlia) or sometimes blue-green algae (e.g. Nostoc, Scytonema, Stigonema). Other plant habitats, not studied in Australia, include tree hollows and pitcher plants. Terrestrial algae are not considered further in this volume.

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Freshwater
Algae