Durations of development and production estimates by two crustacean zooplankton species Thermocyclops oblongatus Sars (Copepoda) and Diaphanosoma excisum Sars (Cladocera), in Lake Naivasha, Kenya

Abstract

Durations of embryonic and post-embryonic development of the two dominant zooplankton crustaceans Thermocyclops oblongatus (Copepoda) and Diaphanosoma excisum in Lake Naivasha were determined at various lake water temperatures to provide the time element for the calculation of their production. Developmental times were temperature dependent in as much as food resource was not limiting. Production estimates were calculated. The turnover times of their biomass was 11.4 and 13.7 days, with production rates of 11.0 and 6.0 μg dw m -3 d -1 for T. oblongatus and D. excisum, respectively. Annual production was estimated as 3302 mg m -3 yr -1 for T. oblongatus and 2176 mg m -3 yr -1 for D. excisum. Production was continuous but with several irregular peaks particularly during the wet seasons when plankton biomass was high.