Integrated biomarker assessment of the effects exerted by treated produced water from an onshore natural gas processing plant in the North Sea on the mussel Mytilus edulis Steven Brooks a,⇑ , Christopher Harman a , Beñat Zaldibar b , Urtzi Izagirre b , Tormod Glette c , Ionan Marigómez b a Norwegian Institute for Water Research (NIVA), Gaustadalléen 21, NO-0349 Oslo, Norway b Cell Biology in Environmental Toxicology Research Group, Department of Zoology and Animal Cell Biology, School of Science and Technology, University of the Basque Country, P.O. Box 644, E-48080 Bilbo, Basque Country, Spain c Det Norske Veritas (DNV), Maries vei 20, 1363 Høvik, Norway article info Keywords: Biomarkers Monitoring Produced water Mussels Passive samplers abstract The biological impact of a treated produced water (PW) was investigated under controlled laboratory conditions in the blue mussel, Mytilus edulis. Mussel health status was assessed using an integrated bio- marker approach in combination with chemical analysis of both water (with SPMDs), and mussel tissues. Acyl-CoA oxidase activity, neutral lipid accumulation, catalase activity, micronuclei formation, lysosomal membrane stability in digestive cells and haemocytes, cell-type composition in digestive gland epithe- lium, and the integrity of the digestive gland tissue were measured after 5 week exposure to 0%, 0.01%, 0.1%, 0.5% and 1% PW. The suite of biomarkers employed were sensitive to treated PW exposure with sig- nificant sublethal responses found at 0.01–0.5% PW, even though individual chemical compounds of PW were at extremely low concentrations in both water and mussel tissues. The study highlights the benefits of an integrated biomarker approach for determining the potential effects of exposure to complex mix- tures at low concentrations. Biomarkers were integrated in the Integrative Biological Response (IBR/n) index. Ó 2010 Elsevier Ltd. All rights reserved. 1. Introduction The chemical composition of produced water (PW) can be very complex and quantitatively variable among PWs, but usually their compounds include trace metals, organic acids, phenols, alkylphe- nols, polycyclic aromatic, aliphatic hydrocarbons and residual pro- duction and treatment chemicals and their breakdown products (emulsifiers, corrosion inhibitors, antifoaming agents, corroded materials, etc.) (Roe Utvik, 1999; Neff, 2002; Johnsen et al., 2004). Most of these compounds usually occur at extremely low concentrations (i.e. [PAHs] total in North Sea PW < 7 lg/L; Strømgren et al., 1995). Moreover, once discharged into the sea, PW is rapidly diluted and dispersed and further volatilization and biodegradation reduces the levels of marine contamination (Flynn et al., 1996). As a result, the chemical identification and quantification of these compounds can be difficult and on most occasions present at concentrations below their detection limit (Smith et al., 1998). In contrast, both acute and sublethal toxic effects have been reported in fish and invertebrates at exposure concentrations below 1% PW (Strømgren et al., 1995; Stephens et al., 1996, 2000; Zhu et al., 2008; Hannam et al., 2009). The groups of PW compounds most likely to be contributing to its toxicity include volatile (BTEX) and semi-volatile (GRO) PAHs, phenols and dissolved ions (Smith et al., 1998; Fisher and Bidwell, 2006). However, in most cases the toxicity can not be attributed to individual components (usually at non-toxic extremely low con- centrations) but to the properties of the mixture. The Ormen Lange gas processing plant is situated at Nyhamna on the island of Gossa, on the West coast of Norway, where pro- duced water, gas and condensate received by pipeline from the Or- men Lange gas field 100 km offshore in the North Sea is processed. Produced water from the onshore processing plant is diluted with cooling water within the Ormen Lange system before it is dis- charged into the surrounding coastal water environment by a sin- gle outfall pipe. Macro porous polymer extraction (MPPE) technology in combination with biological treatment, can reduce dissolved and dispersed hydrocarbons with up to 99% removal, and is used at the Ormen Lange gas processing plant (Aker Kværner, 2006). The MPPE technology and biological treatment can remove most aliphatic hydrocarbons, BTEX, PAHs and NPDs 0025-326X/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.marpolbul.2010.10.007 ⇑ Corresponding author. Tel.: +47 22185100; mob.: +47 92696421; fax: +47 22185200. E-mail address: sbr@niva.no (S. Brooks). Marine Pollution Bulletin xxx (2010) xxx–xxx Contents lists available at ScienceDirect Marine Pollution Bulletin journal homepage: www.elsevier.com/locate/marpolbul Please cite this article in press as: Brooks, S., et al. Integrated biomarker assessment of the effects exerted by treated produced water from an onshore natural gas processing plant in the North Sea on the mussel Mytilus edulis. Mar. Pollut. Bull. (2010), doi:10.1016/j.marpolbul.2010.10.007