The structural and functional diversity of the shallow-water benthic community at New Harbour

The biodiversity of the seafloor community at New Harbour was investigated to determine the structural and functional diversity of the benthic community and resurveyed over two seasons (01-02 and 02-03). A minimum of three sites, separated by at least 50m and accessed through separate dive holes were surveyed. Two 20m transect lines were laid on the seafloor within the 15-25m depth stratum starting from haphazardly chosen starting points. The transects were videoed using a diver-held digital video camera at a fixed height of (a) 70cm above the bottom (for the broader scale analysis of habitat structure) and (b) 40cm above the bottom (to allow for more accurate species identifications). Along one of the 20m transects, core samples were collected from five randomly chosen positions. At each position, two small sediment cores (20mm diam., 50mm deep) were collected, one to determine sediment grain size and benthic chlorophyll a content and one to determine the natural stable isotope signature of the sediment. Also at each position, one large core (70mm diam., 100mm deep) was collected to estimate the abundance and diversity of the benthic macrofauna. Additional collections include: a) three surface sediment scrapes to determine the species composition of microalgae, b) three individuals of each of the numerically dominant epibenthic species, for growth measurements and to determine the stable istope signatures and c) additional specimens of animals and plants and organic material (eg seal faeces) for isotopic analysis to provide a more complete picture of the trophic structure of the community. Algae on the undersurface of the sea-ice were sampled to determine their isotopic signature using five small cores (20mm diam., 100mm deep). Another 9 cores were obtained for the determination of chlorophyll a and species composition of sea-ice algae. Video sampling was stratified by habitat and additional footage was taken of biota in the study area for a general picture of the site. Physical background variables (sea-ice conditions, light colour and intensity) were measured at 15m depth and water currents estimated.