Biological and biogeochemical effects of organic matter and drilling discharges in two sediment communities

Abstract

The present study investigates the relation between community characteristics, input of organic matter and drill cuttings. Drill cuttings are discharged from offshore oil and gas exploration, and settle on soft bottom sediments where the benthic fauna may be affected. In a 3-factorial mesocosm experiment, 2 benthic communities were treated with either water-based drill cuttings or natural sediment in combination with addition or no addition of organic matter, and biochemical and biological responses were studied. The biogeochemical response of organic matter and drill cuttings additions resembled each other, in both cases resulting in enhanced sediment-water fluxes of oxygen, nitrate and ammonium, and reduced concentration of oxygen in sediment pore water. This finding indicated degradation of an organic compound in the water-based drill cuttings. Regarding the biological response, benthic community composition was significantly different for all treatment factors, evidenced by PERMANOVA. Abundance and biomass were reduced in boxes without addition of organic matter, probably as a response to starvation, while abundance and taxa richness were reduced in boxes with drill cuttings. The particular effect of water-based drill cuttings on the environment seems to be complex, and should be investigated further. KEY WORDS: Benthos · Biogeochemical fluxes · Oil exploration · Organic matter · Oxygen microdistributions · Water-based drilling mud Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 442: [23][24][25][26][27][28][29][30][31][32][33][34][35][36] 2011 mental impacts around drilling installations using oilbased and synthetic muds (e.g. Kingston 1987, Neff et al. 1987, Gray et al. 1990, Olsgard & Gray 1995, Daan & Mulder 1996, the use of water-based drilling muds has increased and is currently considered the less environmentally harmful alternative. Waterbased drill cuttings (crushed bed rock mixed with drilling muds) have been considered to have minor or no negative impact on the marine environment except burial (e.g. Hyland et al. 1994, Currie & Isaacs 2005, Netto et al. 2010. However, recent studies have indicated that the effects may be more severe than previously assumed, and that impact factors other than burial trigger the response (Schaanning et al. 2008, Trannum et al. 2010. In light of possible expansion of drilling activities to pristine areas further north and in more coastal, shallow areas, we need to increase our knowledge of the generality of benthic responses.Benthic community composition varies across all spatial scales, but common environmental drivers include sediment characteristics, depth, input of organic matter and temperature (e.g. Gray 1974, Rhoads 1974, Grebmeier et al. 1988, Etter & Grassle 1992, Ambrose & Renaud 1995, Ellingsen 2002, Quijón et al. 2008, Li et al. 2009). A general problem in ecological monitoring is the differentiation of anthropogenic-induced changes from the natural variations constantly occurring in marine comm...

Identification of Fine-Scale Marine Benthic Ecoclines by Multiple Parallel Ordination

“…Increasing species richness and more diverse communities with increasing sediment particle-size is also reported by, for example, Grebmeier et al [9], BuhlMortensen and Høisaeter [67], Newell et al [68], and Trannum et al [69]. Higher species richness at structurally more complex sites because of higher niche diversity also accords with general ecological theory [70].…”

Hydrocarbon contamination affects deep-sea benthic oxygen uptake and microbial community composition

“…Sedimentation by drill cuttings also results in chronic increases in benthic respiration and changes to the structure and functioning of benthic communities (Schaanning et al, 2008;Trannum et al, 2011). Increases in respiration rates reflect the upregulation of compensatory mechanisms in response to hydrocarbon contaminants (Widdows et al, 1995;Olsen et al, 2007b).…”

Detecting the Effects of Deep-Seabed Nodule Mining: Simulations Using Megafaunal Data From the Clarion-Clipperton Zone

“…Frontiers in Marine Science | www.frontiersin.org Tilot, 2006;Amon et al, 2016;Durden et al, 2016;Jones et al, 2017;Simon-Lledó et al, 2019a).…”

“…Neighbouring nodules and other hard substrata, and their associated suspension-feeding organisms, are at risk of being (partially) buried in plume sediments and may be unsuccessful in colonising new locations nearby. Nodules are generally associated with suspension feeders (Tilot, 2006;Vanreusel et al, 2016;Simon-Lledó et al, 2019a).…”