Animal–sediment relationships in an Atlantic Canada marine protected area: Richness, composition and abundance in relation to sediment food indicators

Despite growing concern for biodiversity loss, many coastal areas remain unexplored and their species composition and ecology virtually unknown. This study addressed these issues for intertidal communities of one of the few Atlantic Canada marine protected areas (MPAs). A nested sampling design was used to assess patterns for infauna and indicators of sediment food supply from three main areas of the MPA and from three sites randomly selected within each area. Samples were collected using a 7 cm diameter cylinder (38.5 cm2) inserted 5 cm into the sediment. The data were used to document composition, richness and abundance and to assess their potential relationship with sediment food indicators (organic carbon, total carbon, total N, C : N ratio, and chlorophyllain the sediment). Twenty-eight taxa, primarily deposit-feeding spionid and capitellid polychaetes as well as venerid clams, were the numerically dominant taxa in most areas and sites. Composition and abundance and the concentration of most sediment food indicators differed significantly among areas. Quadratic regression analyses identified several significant relationships (R2≥0.54) between food indicators, primarily organic carbon, carbon and nitrogen contents and several faunistic variables. In general, increases in sediment food supply were correlated with an increase and a subsequent decrease in richness and overall abundance, as well as the abundance of polychaetes and deposit feeders. Food indicators clearly contributed to, but were not the only factors driving spatial variation in community structure. Further studies addressing the physical and biological factors structuring sedimentary communities in MPAs and other coastal areas are encouraged.