Using oligochaetes to monitor the decrease of eutrophication: the 1982-1996 trend in Lake Geneva
Archiv für Hydrobiologie Volume 141 Number 4 (1998), p. 447 - 458
published: Mar 24, 1998
ArtNo. ESP141014104004, Price: 29.00 €
In Lake Geneva (Switzerland), total phosphorus concentrations decreased from a maximum of 89 mg m-3 in 1979 to 41 mg m-3 in 1996. Tubificid and lumbriculid communities were used to monitor the response of deep sediments to this improvement. At a depth of 40 m, mean relative abundance of species indicative of oligotrophic conditions (OS) was 17 % in 1982, 41 % in 1991, and 45 % in 1996. According to OS, Lake Geneva was meso-eutrophic in 1982, but mesotrophic in 1991 and 1996. The rate of recovery was not the same at all depths. Deeper than 40 m, recovery was delayed either by an excess of organic deposition (sediment focusing) or by the persistence of low oxygen concentrations (less than 4 mg 1-1) in the deepest area (285-309 m).