Effects of non-aqueous fluids-associated drill cuttings discharge on shelf break macrobenthic communities in the Campos Basin, Brazil

Abstract

This paper assesses the effects of non-aqueous fluids (NAF)-associated drill cuttings discharge on shelf break macrobenthic communities in the Campos Basin, off the southeast Brazilian coast, Rio de Janeiro State. Samples were taken with a 0.25-m2 box corer from surrounding two oil and gas wells on three monitoring cruises: before drilling, three months after drilling, and 22 months after drilling. Statistical methodologies used Bayesian geostatistical and analysis of variance models to evaluate the effects of the NAF-associated drill cuttings discharge and to define the impact area. The results indicated that marked variations were not observed in the number of families between cruises, though there were changes in the fauna composition. The changes seen in biological descriptors in both control and background situation areas were not considered significant, showing a temporal homogeneity in means. The impact area presented changes in biological descriptors of communities and trophic structure during the three cruises and such changes were correlated to chemical and physical variables related to the drilling activities, as a result of the mix of drill cuttings and sediment and the anoxic conditions established in the substrate. In that area, three months after drilling, a decrease in diversity and an increase in density, motile deposit-feeders and Pol/Crp ratio, and dominance of opportunistic organisms, such as the capitellid Capitella sp., were observed and, 22 months after drilling, an increase of diversity, reduction of dominance of capitellid polychaete, changes in the fauna composition, and a dominance of opportunistic burrowing and tube-building organisms were observed, indicating an ecological succession process.

Effects of the Terra Nova offshore oil development on benthic macro-invertebrates over 10 years of development drilling on the Grand Banks of Newfoundland, Canada

“…Reduced abundance and richness were noted to 0.2 km from a source in the North Sea, with sensitive taxa affected to distances of 0.5 to 1 km (the furthest distance tested against reference conditions) ( Daan et al, 1996). Increased abundance and decreased diversity were noted to 1 km from a drill site off the coast of Brazil (Santos et al, 2010). Neff et al (2000) described results of earlier studies on effects of SBMs.…”

Development of the concept of spatial–temporal mask for testing effects of discharge from well-drilling activities on biological communities

“…This strategy of separating the regions determined the nature of subsequent analyses in the project (Netto et al 2010;Santos et al 2010) for comparing mean intensities of biotic variables between regions, in order to understand the inter-relationships between different variables in all phases of the statistical analysis.…”

“…Biotic (meiofauna and macrofauna) and abiotic (geological and chemical) variables were studied in three sampling periods extending over 2 years (see Netto et al 2010;Santos et al 2010;Corrêa et al 2010;Peralba et al 2010). The first cruise (MS1) before well drilling looked at the initial state of the environment before well-drilling began.…”

A Time Series Study of Lophelia pertusa and Reef Megafauna Responses to Drill Cuttings Exposure on the Norwegian Margin

“…During the last 30 years this industry has progressively increased its operational depth range, and there is interest in extracting oil and gas from strata underlying seafloor supporting CWC reefs. There have been industry funded attempts to gauge exactly how much impact drilling operations may have on benthic fauna [ 23 , 24 , 25 , 26 , 27 , 28 , 29 ], and CWC reefs in particular [ 30 , 31 , 22 , 32 , 33 ]. The direct spatial footprint of drilling operations is small, with the drill shaft and drill well impacting on only a few square meters of seabed and the drill rig anchors impacting on areas of a few hundred square meters [ 29 ].…”