Impact of soil erosion in disturbed tributary drainages on the benthic invertebrate fauna of Lake Tanganyika, East Africa

We analysed the species diversity and distribution of recently buried remains of larval Chironomidae (Insecta: non-biting midges) in bottom environments of Lake Tanganyika adjacent to pristine and disturbed tributary drainages, to investigate the ecological impact of sediment pollution caused by anthropogenic soil erosion. Within each of three drainage size classes (< 10, 30-50, 50-162 km(2)), disturbance has resulted in similar shifts in chironomid species composition which appear to reflect expansion of coarse-grained, low-organic substrates into deeper water, at the expense of the soft organic muds which characterise the deep-water environment. Because the area of habitable lake bottom in Lake Tanganyika is bounded from below by the oxycline, these results indicate that sediment pollution negatively impacts the oxygenated deep-water environment of Lake Tanganyika, and that intensifying soil erosion in tributary drainages may eventually threaten the survival of endemic fish and mollusc species dependent on the habitat it provides. This study establishes the value of sub-fossil Chironomidae as biological indicators of ecosystem health in the large lakes of East Africa. (C) 2003 Elsevier Science Ltd. All rights reserved.