An environmental monitoring study to assess the impact of drilling discharges in the mid- Atlantic. IV. The effects of drilling discharges on the benthic community
Abstract
From the Abstract: “Exploratory drilling at a well site in the shelf break region off Atlantic City, New Jersey, appears to have had several different effects on benthic invertebrates and demersal fish. A zone of visible drilling discharge accumulations (primarily natural subsurface clays) was observed in the immediate vicinity of the well site while elevated levels of clays were detected to 800 m southwest of the site. Fish (primarily hake, Urophycis spp.) and crabs (primarily Cancer borealis) increased substantially between Pre- and Post-Drilling Surveys in the immediate vicinity and to the south of the well site. These organisms may have been attracted to the region as a result of the increased microrelief afforded by the cutting accumulations. The cuttings apparently did not affect the abundance of the sand star (Astropecten americanus) which was the most abundant megabenthic species. High densities of sand stars were observed near the well site, apparently associated with accumulations of mussels (Mytilus edulis) that had fallen from the drilling rig and associated anchor chains.
Sessile megabenthos (pennatulids) and macrobenthos were subjected to burial by drilled cuttings within the immediate vicinity (i.e., within approximately 150 m) of the well site. At the same time, there were also patches of high macrobenthic density around the well site.
Reductions in abundance of macrobenthos beyond the immediate vicinity of the well site are attributed in part to increased predation by fish and crabs and in part to increased clay content of the sediments. No relationships were detected between macrobenthic abundance and the barium content of sediments or the barium content in tissues of organisms, although elevated levelos of barium were detected between the Pre- and Post-Drilling Surveys. The affected areas extended predominantly to the southwest of the well site and, based on observed increases in clay, could be detected to at least 800 m.”