Egg production by the copepod, Eurytemora affinis, in Chesapeake Bay turbidity maximum regions

The copepod, Eurytemora affinis, exhibits maximum abundance in estuarine turbidity maxima (ETMs) of estuaries around the world, including the Chesapeake Bay. We performed egg clutch size (CS) measurements of E. affinis to help understand why this copepod species reaches maximum abundance within ETM regions. Prosome length alone, without any measure of food quantity or quality, was the best predictor for egg CS. The relationship of CS with nutritional variables and the comparison of measured particulate organic carbon concentrations with food requirements predicted from bioenergetics models both suggest that E. affinis egg production is not food limited in Chesapeake Bay ETMs. In addition, nutrition indices based on the seston of the Chesapeake Bay and Choptank River ETMs suggest that food quality was sufficient to support the maximum E. affinis production. Thus, we postulate that abiotic factors, predation and advection limit E. affinis populations in the Chesapeake Bay ETM regions rather than food resources. In Chesapeake Bay ETMs, E. affinis egg production rates began to decrease when temperatures were above approximate to 18C which is similar to results found in laboratory experiments and may help explain the successional dominance switch from E. affinis in winter-spring to the copepod Acartia tonsa in summer.