Ref ID : 3955
Claude Lang; Contrasting responses of oligochaetes (Annelida) and chironomids (Diptera) to the abatement of eutrophication in Lake Neuchatel. Aquat.Sci. 61:206-214, 1998
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Lake Neuchatel (Switzerland) has been recovering from human-induced eutrophication since 1982. Oligochaetes and chironomid larvae were used to monitor the recovery of sediment at a depth of 40 m. In oligochaete communities, the mean proportion of individuals belonging to species indicative of oligotrophic conditions (mostly Spirosperma velutinus and Stylodrilus heringianus) increased from 16% in 1984 to 33% in 1992, but decreased to 11% in 1997. Based on oligochaetes, benthic conditions deteriorated in 1997 whereas, based on the increase of oligotrophic chironomids (mostly Micropsectra), they improved. This difference was attributed to the impact of large planktonic algae whose sedimentation had altered oxygen concentrations at the water-sediment interface. Oligochaetes were more affected than chironomids because they are less mobile and they depend more on the inner sediment for their food and reproduction than the latter. However, based on the combined response of oligochaetes and chironomids, benthic recovery was stalled in 1997 but was not reversed.