Introduction to Freshwater Algae - Freshwater Algae: Identification, Enumeration and Use as Bioindicators - page 20

Table 1.8 Ecological Diversity of Freshwater Green Algae.

Major Ecosystem Specific Conditions Benthic Algae Planktonic Algae

Standing waters - Lakes and
ponds

Wide range of conditions Oedogonium Scenedesmus, Pediastrum,

Tetraedron, Chlamydomonas

Eutrophic to Hypertrophic Cladophora Scenedesmus, Pediastrum.

Oligotrophic Desmids

High (H) and low (L) pH Chara, Nitella (H)

Coleochaete (L)

Mougeotia (L)

Hard water - high (Ca)
concentration

Hydrodictyon

Salt lakes Small unicells, Dunaliella

Standing waters - Wetlands Wide range of conditions Selenastrum Chlamydomonas

Low nutrient, low pH bogs Spirogyra, Mougeotia. Desmids.

Running waters - Streams
and rivers

Wide range of conditions Chlamydomonas

Spirogyra

Hardness (Ca) concentration Hydrodictyon

Running waters - Estuaries,
brackish water

Wide range of conditions Scenedesmus

High salinity Dunaliella

Specialised
microenvironments

Very high nutrients - e.g.
high sewage level

Prototheca Euglena

Chlorella a Endosymbiont in

invertebrates

Associated with Calcareous
deposits

Oocardium stratum

a Also widely occurring as a free-living organism.

( Stephanodiscus ) is replaced in early summer by pop-
ulations of rapidly growing unicellular and small
colonial green algae ( Scenedesmus and Pedias-
trum ), which continue to dominate for the rest of
the annual cycle (Pechar et al ., 2002). Extensive
growth of attached algae (periphyton) may also occur
under high nutrient conditions. Branched thalli of
Cladophora can form extended communities of shal-
low water vegetation along the shores of eutrophic
lakes and streams, breaking off in storms to form
loose biomass which can degrade to generate nox-
ious odours. Another filamentous alga, Mougeotia ,
can form large mucilaginous subsurface growths in
lakes that have been affected by acid rain.

spectrum organisms ( Spirogyra , Chlamydomonas )to
species with very restricted habitats.
Spirogyra occurs in a wide range of habitats, where
it is typically attached to stable substratum (as peri-
phyton) but also occurs as free-floating mats (Lembi
et al ., 1988 - derived by detachment either from
periphyton (vegetative propagation) or from ben-
thic zygotes (sexual derivation). In surveys of North
American sites, McCourt et al . (1986) recorded Spir-
ogyra at nearly one-third of all locations, and Sheath
and Cole (1992) detected Spirogyra in streams from
a wide range of biomes - including desert chaparral,
temperate and tropical rainforests, and tundra.
Other green algae show clear preferences for par-
ticular environmental conditions (Table 1.8) that
include degree of water movement (lentic vs. lotic
conditions), inorganic nutrient status (oligotrophic
to eutrophic), pH, hardness (Ca concentration)
and salinity. These conditions frequently occur in
combination, with many moorland and mountain

Species preferences

Individual species of green algae differ considerably
in their ecological preferences, ranging from broad