Population dynamics of the chydorid cladocera of a Southern Michigan Marl Lake

The seasonal population dynamics are described for 21 chydorid species in two shallow Scirpus subterminalis beds of Lawrence Lake, Michigan, USA. Six species were rare; four species were predominantly abundant. The dynamics of the populations followed no consistent pattern among the species. However, each species, with one exception, may follow the same pattern from year to year. Eight species overwintered under the ice as parthenogenetic individuals. Populations of Alonella excisa may be greatly reduced during the summer months because of competition with A. exigua.