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 4. Filamentous benthic or suspended mats - Filamentous green algae such as
Spirogyra or cyanobacteria such as Anabaena or Lyngbya.
The common nuisance algae in lakes were named Annie, Fannie and Mike after Anabaena,
Aphanizomenon, and Microcystis, three noxious cyanobacteria noted for forming `blooms' and
surface scums in many lakes considered to be eutrophic. In addition the algae also include numerous
groups such as Euglenophyta (Euglena), Chlorophyta (Chlamydomonas, Volvox, Oedogonium,
Spyrogira, Zygnema), Chrysophyta (Diatoms, Mallomonas), and the Pyrrophyta (dinoflagellates)
which inhabit the diverse habitats present in most lakes.
II. Animals - (neglecting waterfowl, mammals, and amphibians)
A. Swimmers - nekton - capable of moving against water currents
1. anadromous fish - river and stream spawners
2. catadromous fish - ocean spawners
3. pelagic - inhabiting the open deeper waters
4. littoral - inhabiting the shoreline shallows
B. Weak swimmers, zooplankton - capable of moving but not against modest currents
1. Copepods - mostly grazers, cyclopoid most common in lakes,
example Cyclops, Diaptomus.
2. Crustacea - grazers and predators, numerous examples including Cladocera
(Daphnia, Bosmina), Ostracoda
3. Rotifera - rotifers such as Keratella, often much smaller than other zooplankton,
mostly grazers, may be major component of reservoirs
4. meroplankton - organisms inhabiting the plankton only during part of life
cycle, often as larvae. Clams, insects.
5. ichthyoplankton - larval fish
C. Insects - meroplankton
1. Chironomidae - midge larvae often red with haemoglobin, especially in anoxic
sediments.
2. Chaoboridae - Chaborus may be most important single insect in some reservoirs.
Called phantom midge, has complex migration pattern through the water column on a
diel basis.
D. The Benthos
1. insects - includes the above insects as well as Trichopterans (caddisflies),
Ephemeroptera (mayflies), and others.
2. worms - Oligochaeta, true worms. Often indicators of undesirable sediment
qualities when found as dominant form.
1.2-29
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