The zooplankton community in a small, hypertrophic mediterranean reservoir (Foix reservoir, NE Spain)

Abstract

A small hypertrophic reservoir (Foix Reservoir, Spain) was sampled from March 1997 to January 2000 to document the composition and spatial and temporal variability of the zooplankton assemblage. Twenty five species of Rotifera, 10 of Cladocera, and one species of copepod (Acanthocyclops robustus (Sars)) were collected. The most abundant rotifer species were Brachionus angularis (Gosse) and Polyarthra spp. Daphnia galeata Sars, Ceriodaphnia quadrangula (Muller), and Chydorus sphaericus (Muller) were the main cladocerans. For each species, brief information is given on ecology, distribution, and occurrence in Spain and in the Foix Reservoir. The zooplankton community of the Foix Reservoir was characterized by the abundance of heleoplanktonic species, which accounted for 50 % of the taxa. Remarkable changes over time in species’ composition and occurrence were found for Rotifera and Cladocera during the study period. A. robustus showed high density and biomass values throughout the sampling period. In the summer of 1999, copepods avoided deep layers, whereas some Rotifera (Polyarthra spp,, Filinia spp,, Brachionus angularis) and Chydorus sphaericus were found near the anoxic bottom. A rare rotifer in the Iberian Peninsula, Itura aurita aurita (Ehrenberg), was also found in lotic sections of the reservoir.