Résumé
Gut fluorescence, feeding and egg production rates of zooplankton assemblages were measured in a shallow, eutrophic brackish-water pond for 24 days. Brachionus plicatilis, Hexarthra intermedia and Apocyclops panamensis successively developed and exhibited differences in food selectivity. Rotifers selected small particles but also had a preference for larger particles (15–21 μm, Equivalent Spherical Diameter, ESD). B. plicatilis appeared less selective than H. intermedia, which fed mostly on particles <6 μm. A. panamensis adults showed a selectivity for 6–21 μm ESD particles. Laboratory experiments suggested that A. panamensis adults were able to shift from seston to carnivorous feeding, depending on the availability of these food resources. Measurements of gut fluorescence and grazing gave comparable ingestion rates. Rotifers displayed the highest ingestion rates (up to 486% body C d-1). Despite high total phytoplankton and seston biomasses, the high ingestion rates and selective grazing of rotifers induced auto food-limitation phenomena and caused major changes in seston abundance and size structure. Grazing impact was less important when A. panamensis dominated.