Benthic species diversity along a depth gradient: Boston Harbor to Lydonia Canyon

Benthic infaunal samples collected from depths ranging from 5.9 to 2180 m, from nearshore in Boston Harbor to offshore on the continental slope off the coast of Massachusetts, USA, were evaluated for changes in diversity with depth using expected species at a subsample size of 100, ES(100), as well as Fisher's log-series alpha. All samples were processed with fine mesh (0.3 mm) screens and identified by the same team of researchers, who provided a high and comparable level of expertise. Both measures of diversity were made at the single sample level. An analysis of the variation in these measures, based on a linear mixed model, showed that the largest source of variation was due to depth followed by stations within the same depth range. Variation between cruises/years was relatively small. Communities from the shallowest harbor stations out to 168 m at the edge of the continental shelf had a wide range of diversities, but exhibited no apparent pattern of change with depth or sediment type. The highest diversities were found at mid-slope depths (1220–1350 m). Diversities at 2065–2180 m overlapped with those from mid-slope depths, but were generally lower.