MEPS 205:229-240 (2000)  -  doi:10.3354/meps205229

ABSTRACT: In marine soft-bottom benthic habitats, the disappearance of opportunistic species as succession proceeds following an enrichment or disturbance event is thought to be due to the exhaustion of a food resource. To further investigate this hypothesis, feeding rate, growth rate, and reproductive output (measured as embryo number and size) of the opportunistic deposit-feeding polychaete Capitella sp. I were measured in sediments with different protein concentrations but the same protein source. Feeding rates progressively increased as protein concentration increased over the range of 0.2 to 4.7 mg g^-1; thereafter, feeding rate was constant up to a sediment protein concentration of 8.1 mg g^-1, the highest used in these experiments. This response is not consistent with the predictions of optimal foraging theory, as applied to deposit feeders. Growth rate showed a similar pattern, progressively increasing then reaching a plateau at ~23% d^-1 in sediments with 4.6 to 4.7 mg protein g^-1. Capitella sp. I showed decreased fecundity and longer generation times (embryo sizes were not significantly different) in sediments with lower protein concentrations and did not reproduce in sediments containing <1 to 2 mg g^-1. These results support the hypothesis that the disappearance of Capitella sp. I as succession proceeds is due to decreased fitness in sediments with lower food concentrations and an inability to reproduce in sediments below a threshold protein concentration. Systematically documenting how variations in sediment protein concentration affect the acquisition (feeding rate) and utilization (growth rate, reproductive output) of food resources by benthic invertebrates with different life-history strategies will help to elucidate important factors influencing the distribution of individuals and species in the benthos.

KEY WORDS: Capitella sp. I · Deposit-feeding · Feeding rate · Functional response · Growth rate · Opportunistic species · Polychaetes · Sediment organic concentration