engleski

Long term changes in the crustacean plankton of the shallow mediteranean lake

Shallow Mediterranean lake Jezero has been affected by eutrofication in last four decade. In 1970 the lake has been a subject of phosphorus reduction program with bio manipulation techniques to decrease lake primary production. In the 1974 and 1976 herbivorous and planktivorous fish (silver carp, grass carp) were introduced in the lake. We measured the abundance and biomass of filter-feeding micro crustacean zooplankton, their grazing impact on phytoplankton biomass, and compared it with the results of prebiomanipulation state. Although the species composition remained the same, we observed a shift in the portion of certain taxa in total abundance of crustacean plankton. Large daphnias and calanoid copepods became dominant, while cyclopoid copepods and Bosmina became scarce. Phosphorus reduction lowered phytoplankton biomass, but submerged vegetation was also limited by the lack of phosphorus. Our results indicate that the importance of zooplankton grazing may have minor importance for the maintenance of the clear water state in the lake.

zooplankton; phytoplankton; shallow Mediterranean lake

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