Seasonal Patterns in the Zooplankton Community of a Eutrophic Lake in Eastern Washington Prior to Multiphased Restoration

Abstract

ABSTRACT The zooplankton community of eutrophic Liberty Lake, Washington was investigated at two pelagic stations for a period of one year prior to the initiation of a multiphased lake restoration treatment. Analysis of the microinvertebrate population formed an integral part of an intensive limnological investigation of the physical, chemical, and biological characteristics of the lake prior to, during, and following a series of restoration treatments completed during 1980–81 (Funk et al. 1980). Seasonal variations in the composition, density, and biomass of the major groups and species of the zooplankton are discussed in relation to patterns observed in other localities. The rotifers numerically dominated the community throughout the study period with the species Keratella cochlearis, Kellicottia longispina and Polyarthra spp. making up the largest share of zooplankton density. Cladocerans, primarily Daphnia pulex and D. galeata mendotae, accounted for the largest portion of total biomass. Copepods assumed an intermediate position between the other two groups in terms of both density and biomass. Effects upon the lake zooplankton community following the alum application phase of the lake restoration project are also presented based on preliminary data obtained during and after the treatment.