Effects of sediment particle size composition on survivorship of benthic invertebrates from Lake Tanganyika, Africa

Increasing sediment loads entering Lake Tanganyika owing to widespread catchment deforestation are hastening the need for increased understanding of the effects of influent sediment composition on biotic community structure. Two ex situ experiments were done investigating the effects of exposure to sediments of differing particle size ranges on survivorship of two model groups of benthic invertebrates, gastropods and ostracods, from the lake. In both experiments, it was found that survival rates decreased with decreasing sediment particle size. Gastropod feeding behaviour was also affected significantly by sediment particle size, !;bowing increasing severity of impact with decreasing particle size. In addition, a detrimental effect of experimentally increased sediment loads on gastropod survivorship, irrespective of sediment texture, was found. These results suggest that runoff from sub-catchments with soil or bedrock that weathers to produce fine-grained sediments may have disproportionately detrimental effects on littoral biota in Lake Tanganyika, and, thus, have important implications for ecosystem and biotic community structure.