Ref ID : 1655
Claude Lang and Olivier Reymond; Reversal of eutrophication in Lake Geneva: evidence from the oligochaete communities. Freshwater Biology 28:145-148, 1992
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1. In Lake Geneva (Switzerland), total phosphorus concentrations have decreased from 90 mg m-3 in 1979 to 55 mg m-3 in 1990. 2. To assess the effects of this improvement, tubificid and lumbriculid communities were sampled in 1982 and in 1991 in the same areas, at a depth of 40 m. 3. Abundance of mesotrophic species (mostly Potamothrix vejdovskyi) and of eutrophic species (mostly Potamothrix hammoniensis) was lower in 1991 than in 1982; in contrast, oligotrophic species (mostly Peloscolex velutinus) were more abundant in 1991 than in 1982. 4. The changes recorded in 1991 were the same as those associated with a decrease of organic sedimentation. 5. Mean relative abundance of oligotrophic species increased from 17% in 1982 to 41% in 1991. According to these values, Lake Geneva was meso-eutrophic in 1982, but mesotrophic in 1991.