Epibenthic community variability in the northeastern Chukchi Sea

Epibenthic organisms can occur in large numbers and high biomass on the continental shelf of the northeastern Chukchi Sea. From an ecosystem perspective, epibenthic organisms are important in recycling and redistributing organic matter deposited from the pelagic zone, and they also are key members of the local food web. Data for biological (epibenthic species composition, abundance, and biomass) and environmental (bottom water temperature, salinity, dissolved oxygen and pH, sediment grain size, sediment organic matter and sediment chlorophyll content, latitude, longitude, and water depth) variables were collected at 53 stations in the northeastern Chukchi Sea during the summers of 2009–2010 to characterize the epibenthos and provide a benchmark for potential future changes due to possible anthropogenic disturbances. Community biomass, abundance, species composition and taxa richness varied in patches throughout the study area, but were generally dominated by crustaceans and echinoderms. These two groups had an inverse relationship in the distribution of their dominance. Communities dominated by crustaceans had significantly higher Simpson's dominance and Pielou's evenness values compared to echinoderm-dominated communities. Correlation coefficients for six environmental variables (longitude, bottom water temperature, water depth, bottom water dissolved oxygen, sediment grain size 2 phi and total organic carbon) with epifaunal abundance and biomass were moderate (0.42 for abundance and 0.51 for biomass at a significance level of 0.1%). However, assemblages within the study area followed a distinct spatial distribution pattern that matched the path of important water masses in the region.