These lake ecosystems are relatively low in diversity, particularly at higher trophic levels. The phytoplankton of most natural lakes are dominated by Chrysophyte algae, although a broad range of other groups are represented and may dominate under various conditions. The zooplankton are dominated by rotifers and small crustaceans (eg. Diaptomus minutus, Bosmina longirostris), perhaps because they are less susceptible to visual predators in the clear waters. The benthic invertebrates include numerous species of chironomids, amphipods (eg. Hyalella azteca) and crayfish (Orconectes virilis). Typical fish communities include several minnow species, white suckers (Catostomus commersoni), and a top predator such as northern pike (Esox lucius) or lake trout (Salvelinus namaycush). In some smaller lakes, lake whitefish (Coregonus clupeaformis) or yellow perch (Perca flavescens) may represent the top of the exclusively aquatic food chain. In addition, the food chain in most lakes will include common loons, perhaps some common mergansers, a few ring-billed gulls, an occasional great blue heron, bald eagle or osprey, and smaller birds including belted kingfishers, and tree swallows and other insectivores. Also, many lake ecosystems may include such mammals as beaver, otters, pine martens, fishers, mink and weasels as regular or occasional components.
Listings of common aquatic species naturally occurring in the ELA are available on request. Particularly detailed taxonomic information is available for the phytoplanktonic and benthic algae, for the zooplanktonic crustaceans and rotifers, for the benthic invertebrates (particularly chironomids), and for the larger fish species.