Vertical Distribution and Seasonal Abundance of Zooplankters in Lake Tanganyika

Abstract

Vertical distribution and seasonal abundance of zooplankters were studied in Lake Tanganyika. Faunal composition of zooplankton was simple. Limnocnida tanganicae, copepod nauplii, Diaptomus simplex, cyclopoids, and shrimp were collected by closing nets. Nauplii were dominant in number, but cyclopoid copepodites were dominant in biomass. The biomass calculated was in the range of 1.2-3.7 (average 2.3) g/m² excluding shrimp and medusa. For the vertical distribution of the copepods, the larger the size, the deeper the layers they stayed in the daytime, and the more remarkable diel vertical migration they showed. Chlorophyll a amount was high at the end of September and in October, which coincides with the bloom of Anabaena and Dictyosphaerium off Myako. The time of phytoplankton boom off Myako seemed to correspond with that of other parts of the lake as cited in the literature. The number of Diaptomus females with eggs increased in September and October, and the number of shrimp also increased in October. The increase of Diaptomus females with eggs corresponded with phytoplankton abundance. The seasonal abundance and high reproduction of zooplankters seemed to be a product of the abundance of phytoplankton in Lake Tanganyika.