Post-mortem erosion of fine-scale spatial structure of epibenthic megafauna on the outer Grand Bank of Newfoundland

Abstract

Marine organisms exhibit spatial variability at scales ranging from thousands of kilometres (biogeographic variability) to a few body lengths. Physical processes can increase spatial variability through selective sorting, or decrease it through mixing. We examine the effects of post-mortem processes on the spatial structure of empty shells and tests left by populations of molluscs and echinoderms on outer Grand Bank. Analysis of data from five photographic transects showed that spatial variability of shells and tests decreased relative to live organisms of the same species at scales greater than 140 m. Spatial variability did not increase relative to live specimens, with the exception of urchin tests at a scale of 20–30 m on two of five transects. We postulate that selective transport of shells does not occur in this environment at scales from 15 to 1500 m.