Marine Science

Marine Science

Senior Theses 2004

Rebekah Duncan (2004). Grazing habits of the estuarine copepods Eurytemora affinis and Acartia tonsa in turbid and non-turbid environments in Chesapeake Bay.
Faculty advisor: Jeannine Lessmann


The estuarine copepods Eurytemora affinis and Acartia tonsa are usually spatially separated in Chesapeake Bay and its tributaries, with E. affinis dominating the estuarine turbidity maximum (ETM) and A. tonsa dominating less turbid regions seaward of the ETM. To investigate the possible role of feeding in this niche partitioning, two replicate 24 h cross-feeding incubations were performed. Eurytemora affinis was collected from the Choptank River ETM (ETM), while A. tonsa was collected from the Horn Point Laboratory pier seaward of the ETM (non-ETM). Feeding was evaluated by gut fluorescence and microscopic enumeration of prey before and after the grazing period. Acartia tonsa carbon-specific ingestion rates were severely depressed in ETM water versus non-ETM water. Feeding by E. affinis was similar in both water types, with significantly higher ingestion rates than A. tonsa in ETM water (Experiment 2 only) and comparable rates to A. tonsa in non-ETM water. These results suggest that the high turbidity of the ETM may inhibit the feeding of A. tonsa but not E. affinis, thus helping to explain their distributions.

Student Research