Effect of the toxic dinoflagellate Gymnodinium catenatum on the grazing, egg production, and hatching success of the copepod Acartia clausi

The influence of the toxic dinoflagellate Gymnodinium catenatum Graham on the reproductive response of the calanoid copepod Acartia clausi Giesbrecht was examined. Mature females of A. clausi were selected and fed a mixture of natural phytoplankton and G. catenatum in nominal ratios of 100:0%, 75:25%, 50:50%, 25:75%, and 0:100%, respectively. The concentration and type of toxins of the G. catenatum strain used were evaluated. The ingestion of G. catenatum did not produce either adverse effects nor incapacitation of A. clausi. Ingestion and egg production rates were not diminished by G. catenatum and were highest at the 0:100% ratio. Egg hatching rates were similar (>90%) for all diets. Acartia clausi is an ubiquitous copepod in Concepción Bay (Baja California Sur, Mexico), and our results indicate that it was able to feed on this toxic dinoflagellate at rates similar or higher than those at which it feeds on natural phytoplankton; therefore, A. clausi could play a key role in controlling the occurrence of red tides in Concepción Bay.