Spatial and temporal patterns of zooplankton standing biomass and production in Lake Malawi

Standing biomass and production of crustacean zooplankton was measured from ten full-lake sampling cruises on Lake Malawi during 1992-3. Stage-specific development rates and dry weights were measured in the laboratory for the dominant species. Mean total standing biomass estimates for the whole lake ranged from 0.9 to 2.4 g dry wt m(-2). Overall mean biomass for the two years was 1.6 g dry wt m(-2). Total production estimates for the three dominant copepod species ranged from 66 to 210 mg dry wt m(-2) d(-1), with an average annual production of 49 g dry wt m(-2) y(-1). Maximum biomass and production rates were recorded in the south of the lake, although for copepods this was not marked and there was little consistency in their horizontal distribution. Cladocerans, however, were almost always more prevalent in the extreme south of the lake than elsewhere. The temporal pattern of zooplankton production showed marked seasonal variation, with maximum production after the onset of the S. E. trade winds and associated with increases in phtyoplankton abundance.