This review paper identifies the main effects of oil and gas drilling waste on benthic environments. We identified 26 papers and technical reports that surveyed sediment samples from 72 production or exploration platform sites to assess the zone of influence of sediment contamination and biological effects on benthic communities. While oil-based fluids are now rarely used in the marine context, their release has had large-scale (out to 6 km) and persistent (decadal time scale) impacts on benthic communities. The zone of influence of water-based drilling fluids as determined by sediment barium concentration was larger (2 to 20 km) than for synthetic-based fluids (200 to 2000 m). The zone of biological effects on benthic community diversity and abundance ranged from 100 to 1000 m for both water and synthetic fluids. Effects include changes in benthic species diversity, abundance and alterations to community structure. Functional changes included a loss of suspension-feeding species and increases in deposit feeders and polychaetes. In general, this review demonstrates a loss of benthic biodiversity and suspension-feeding communities due to oil exploration and production and the potential for large-scale effects on sensitive communities such as deep-sea, coral and vegetated habitats. Current research gaps and priorities are identified.KEY WORDS: Benthic community composition · Chemical toxicity · Organic enrichment · Suspended sediments · Oil-based fluids · Synthetic-based fluids · Water-based fluids Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 456: [285][286][287][288][289][290][291][292][293][294][295][296][297][298][299][300][301][302] 2012 charged directly at sea. The third step includes the installation of a blow-out preventer on top of the wellhead which controls formation pressures. Additionally, a marine riser is installed that allows all drilling fluids and cuttings to be pumped up through the riser and back to the oil platform or drilling ship. The remaining sections of the well are then drilled to reach the oil reserve.Drill cuttings are produced by the grinding action of the drill bit and range in size from clay-sized particles to coarse gravel, having a mineralogy reflecting that of the drilled strata (Neff 1987, 2005, Trannum et al. 2010. Drilling muds lubricate the drill string, bring up cuttings from the well hole, control internal pressure and stabilize the well and constitute 5 to 25% of the discharged drill fluids (Trannum et al. 2010).There are 3 main types of drilling mud: oil-based, synthetic and water-based fluids (OBF, SBF, WBF). In oil-based mud, the dominant fluid is a mineral oil; in synthetic mud it is ester, ether, acetyl or olefin; and in water-based mud, fresh or salt water is used. Drilling muds also contain a weighting material, clay or an organic polymer, various inorganic salts, solids and organic additives (Neff 2005). Barite (BaSO 4 ) has been the most frequently used weighting material. More recently, ilmenite (FeTi...
Environmental assessments (EAs) predict project environmental effects with varying degrees of certainty. Articulating prediction uncertainty and linking it to EA follow-up is a best practice for reducing uncertainty. This study examines predictions from Canadian oil projects off Newfoundland and Labrador between 1985 and 2012 concerning seabirds, the valued ecosystem component identified as the most vulnerable to oil exploitation in an area frequented by millions of migratory birds. We asked if these EA predictions: (a) reported uncertainty ratings; (b) for those reporting medium and high uncertainty ratings whether the predictions were addressed by EA follow-up; and (c) if prediction uncertainty was reduced by EA follow-up and reflected in subsequent EAs. Prediction uncertainty reporting was rare and uncertainties were not resolved through EA follow-up. Assumptions of negligible or low environmental effects on seabirds off Newfoundland and Labrador from offshore oil and gas extraction have been supported through decades by sustaining uncertainty.
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