[Variations of zooplankton abundance and biomass in a tropical oligo-mesotrophic reservoir in Northern Venezuela].

Zooplankton abundance in reservoirs is mainly determined by the speed and content of the water, but relatively little is known regarding tropical reservoirs. We studied the seasonal and spatial distribution of zooplankton abundance and biomass along the longitudinal axis of Clavellinos reservoir, northern Venezuela, from October 2006 to September 2007. Zooplankton was collected from the oxygenated layer using a plankton net. A total of 16 taxa were identified: Copepoda, Cladocera, Rotifera, Ostracoda and Diptera. Thermocyclops decipiens (Copepoda, Cyclopoida) dominated the community, while rotifers were the most diverse, with 10 species. Zooplankton abundance varied from 31 to 101 ind/L in E1, 36 to 84 ind/L in E2, and, from 30 to 250 ind/L in E3. Biomass varied from 97.4 to 1406.3 microg/l in E1, 108.5 to 397.2 microg/l in E2, and from 25.9 to 763.9 microg/l in E3. This zooplankton community seems to respond to environmental variations in the reservoir, rather than to variations in resource availability.