Abstract
During four cruises to the Mississippi River plume in the winters of 1981-83, we examined the effects of ambient suspended sediment concentrations (11.4-95.2 mg l super(-1)) and natural phytoplankton assemblages (300-247,800 cells l super(-1)) on the feeding rates of Acaria tonsa, Centropages velificatus, and Eucalanus pileatus. A. tonsa ingested cells in proportion to their abundance and there was no evidence of saturated feeding at the highest cell concentrations. Ingestion rate of A. tonsa was not affected by the concentration of suspended particulates up to 95.2 mg l super(-1). In 5 of 6 paired feeding experiments (n = 6), where conditions were exactly the same for both species, there was no significant difference (p < 0.05) in the ingestion rates of A. tonsa and C. velificatus. Ingestion rates of E. pileatus were also, to some extent, proportional to the phytoplankton cell concentration (regression coefficient = 0.74). In similar paired comparisons (n = 8) between E. pileatus and C. velificatus, ingestion rates of E. pileatus were significantly greater than those of C. velificatus except at the two highest concentrations of suspended particulates. It should be noted, however, that E. pileatus was never collected when suspended particulates were greater than 41.9 mg l super(-1). (DBO)