In situ experiments on the effects of increased sediment loads on littoral rocky shore communities in Lake Tanganyika, East Africa

1. Two in situ experiments investigated the responses to artificially increased sediment loads of the gastropod and fish communities, and of the whole benthos, of the rocky shores of Lake Tanganyika. Sediments were emptied once onto randomly selected quadrats using SCUBA, with control quadrats receiving no addition of sediment. Quadrats were monitored up to 6 months after sediment addition. 2. While the abundance of Lavigeria grandis (Mollusca; Gastropoda) was reduced greatly by the addition of sediment, low abundance and biomass of the whole gastropod community on sediment‐impacted quadrats 6 months after sediment addition suggests more general impacts of inundation in the longer term. 3. Benthic invertebrate communities inundated by sediment had significantly fewer individuals and numbers of taxa than control communities. No significant community recovery was recorded on sediment‐impacted quadrats within the timescale of the experiment. A short‐term period of high turbidity brought about by the emptying of sediments onto sediment‐impacted quadrats also caused severe decreases in benthic invertebrate abundance on controls 10 days after sediment addition. This suggests that even short‐term pulses of sediment may have significant detrimental effects on littoral communities. 4. Although significant impacts of sediment on fish community dynamics were found, and a significant reduction in the number of benthic algivorous species was recorded immediately after sediment addition, littoral fish communities showed strong resistance overall to the addition of sediments. This apparent resistance, however, may be a consequence of the small scale at which the experiment took place. Littoral fish communities were also shown to be more dynamic than indicated previously.