Benthic Studies in Buzzards Bay. I. Animal‐Sediment Relationships1

Abstract

During October and November 1955 a bottom faunal study was undertaken at 19 localities in Buzzards Bay, Massachusetts. The number of animals ranged from 1,064 to 12,576/m² with a mean number of 4,430. In comparison with certain other areas these numbers appeared small and seemed to be due to the relatively low concentrations of chemical nutrients and modest primary production of the region. Two faunal assemblages were recognized: one, present in the muddy sediments and dominated by the lamellibranch Nucula proxima and the polychaete Nephthys incisa was essentially the same community described from Long Island Sound; the other, restricted to the sandier sediments and characterized by species of the amphipod genus Ampelisca. The two primary feeding types, the filter‐feeders and the deposit‐feeders, numerically dominated in the sand and mud sediments, respectively. The distribution of certain dominant deposit‐feeders in Long Island Sound and Buzzards Bay was poorly correlated with the silt‐clay fraction of the sediment. However, when clay alone was used, a much better agreement was obtained. It was suggested that clay is probably the most valid criterion for the distribution of deposit‐feeders. The distribution of infaunal filter‐feeders seemed related to the degree of sorting and the median grain size of the sediment, with largest populations present in well‐sorted fine sand. The hydrodynamic implications of this distribution are discussed.