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Marine Ecology Progress Series

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MEPS 442:23-36 (2011)  -  DOI:

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

Hilde C. Trannum1,*, Hans C. Nilsson1,2, Morten T. Schaanning1, Karl Norling1,3

1Norwegian Institute for Water Research (NIVA), Gaustadalléen 21, 0349 Oslo, Norway
2Department of Aquatic Resources, Swedish University of Agricultural Sciences, Turistgatan 5, 453 30 Lysekil, Sweden
3Department of Biology, University of Oslo, PO Box 1066 Blindern, 0316 Oslo, Norway

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

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Cite this article as: Trannum HC, Nilsson HC, Schaanning MT, Norling K (2011) Biological and biogeochemical effects of organic matter and drilling discharges in two sediment communities. Mar Ecol Prog Ser 442:23-36.

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