The fauna of the HEBBLE site: patterns in standing stock and sediment-dynamic effects

Abstract

At the High Energy Benthic Boundary Layer Experiment (HEBBLE) site at 4820 m depth on the Nova Scotia Rise (40°27′N, 62°20′W), abundances of polychaetes, bivalves, tanaids, and isopods were conspicuously greater than expected for the depth, whereas those of nematodes and harpacticoids, the two dominant meiofaunal taxa, were not. Further, the abundances of polychaetes, bivalves, tanaids, and nematodes were consistent over time and appeared to be unaffected by the periods of strong near-bottom flow that characterized the site. In contrast, isopods and harpacticoid copepods were less abundant in samples taken as a storm abated, apparently because they were eroded during benthic storms. We explore implications of the difference between macrofaunal and meiofaunal abundance for community structure. In addition, because a goal of the HEBBLE project was the parameterization of sediment transport in the deep sea, we summarize ways that the biota affects sediment transport at this high-energy site.