Flocculation and accumulation of fine drilling waste particulates on the scotian shelf (Canada)

Concern over the potential environmental effects of oil and gas exploration on productive offshore banks has been pronounced on the north-east coast of North America. The sensitivity of the commercially exploited finfish and shellfish stocks (especially the sea scallop Placopecten magellanicus)on Georges Bank has prompted the adoption of a drilling moratorium until the year 2000 by both the Canadian and United States governments. In Canada, the moratorium will come under review starting in 1996 and the Department of Fisheries and Oceans (DFO), with funding from the Program on Energy Research and Development, has initiated a study of processes related to the potential impacts of drilling waste solids. Recent re-analyses of benthic community data from the North Sea have shown that the cumulative effects of drilling waste discharges may extend further from the platforms than was previously accepted (Reiersen et al., 1989; Gray et al., 1990; Olsgard & Gray, 1995). The cited studies focused on what was detectable within the sea-bed sediments. To date, no examination has been made of the effects of discharges on suspended particulate matter (SPM) concentrations in the region just above the sea-bed (the 'benthic boundary layer'). A major aim of our programme has been to characterize this region and to assess the potential for impacts on P. magellanicus from drilling waste discharges.