PAH body burden and biomarker responses in mussels (Mytilus edulis) exposed to produced water from a North Sea oil field: Laboratory and field assessments Rolf C. Sundt a,⇑ , Daniela M. Pampanin a , Merete Grung b , Janina Baršiene ˙ c , Anders Ruus b a IRIS – International Research Institute of Stavanger, P.O. Box 8046, N-4068 Stavanger, Norway b Norwegian Institute for Water Research, Gaustadalléen 21, NO-0349 Oslo, Norway c Institute of Ecology Nature Research Center, Akademijos 2, 08412 Vilnius, Lithuania article info Keywords: Produced water Mussel Lysosomal membrane stability Micronuclei Bioaccumulation Monitoring abstract In order to study the impact of produced water (PW) from a North Sea oil field on blue mussels (Mytilus edulis), chemical and biological markers were selected. A laboratory exposure (0.125%, 0.25% and 0.5% of PW) and a field study (6 stations 0.2–2 km from a PW discharge point) were conducted. In the laboratory study, PAH bioaccumulation increased in mussel soft tissue even at the lowest exposure dose. Micronu- clei frequency demonstrated a dose–response pattern, whereas lysosomal membrane stability showed tendency towards a dose–response pattern. The same markers were assessed in the field study, bio- marker analyses were consistent with the contamination level, as evaluated by mussel polycyclic aro- matic hydrocarbons body burden. Overall, obtained results confirmed the value of an ecotoxicological approach for a scientifically sound characterisation of biological effects induced by offshore oilfield oper- ational discharges. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction Operation of oil and gas production platforms in the North Sea result in considerable discharges of produced water (PW). This consists of a mixture of formation water contained naturally in the reservoir, injected water used for secondary oil recovery and treatment chemicals added during production (Røe Utvik et al., 1999). The chemical composition varies both between reservoirs and within a reservoir as production proceeds. A chemical charac- terisation of four offshore oil production platforms in the North Sea showed that the major organic components were BTEX (benzene, toluene, ethylbenzene and xylene), NPD (naphtalenes, phenan- threnes and dibenzothiophenes), polycyclic aromatic hydrocar- bons (PAHs), organic acids, alkylphenols (APs) and phenols (Røe Utvik, 1999). Some of the present organic chemicals have the po- tential to bioaccumulate and may be toxic for organisms living in the vicinity of platforms (Tollefsen et al., 1998; Aas et al., 2000; Gorbi et al., 2008; Hannam et al., 2009; Farmen et al., 2010; Perez-Casanova et al., 2010). As a chronic source of pollution, PW is also a source of concern with respect to possible long term impact on the environment (Neff et al., 2006). Estimates of the PW discharge volume predict an increase on the Norwegian shelf until 2010–2014, reaching about 200 million L/year (OLF, 2007). There is therefore a need for adequate exposure and effect markers used in biomonitoring of offshore discharges (Hylland et al., 2008; Farmen et al., 2010). PAHs in particular are known to induce toxic effects at the individual level (van der Oost et al., 2003; Bellas et al., 2008). Therefore, integration of chemical analyses with biomarker re- sponses in organisms has been recommended for monitoring off- shore exploitation activities (Hylland et al., 2008). Previous studies have indicated that toxic compounds are detectable sev- eral kilometres away from a North Sea oil production platform using in vitro bioassays and biomarkers (Hylland et al., 2006b). Although there is reason to assume that many PW related chem- icals may produce biological responses, the ability to assess the potential for adverse effects is limited by the lack of sufficient in situ biomonitoring data and realistic laboratory exposures. A two-tier approach has been proposed to make the biomonitoring tools suitable for application purposes, aiming to build a cost- effective strategy. It contains a tier 1 screening level with sensi- tive low-cost biomarkers (e.g. lysosomal membrane stability (LMS)) and a tier 2 stress syndrome assessment level applying a battery of biomarkers when an environmental alteration is re- corded at tier 1 (Viarengo et al., 2007). For standardisation pur- poses, the use of caged animals (mussel and/or fish) is also suggested (Cajaraville et al., 2000; Handy et al., 2003; Hylland et al., 2008). Mussels (Mytilus sp.) have been widely used since the 90s, and have been shown to be one of the most successful 0025-326X/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.marpolbul.2011.04.009 ⇑ Corresponding author. Tel.: +47 51875500; fax: +47 51875540. E-mail address: rolf.sundt@iris.no (R.C. Sundt). Marine Pollution Bulletin 62 (2011) 1498–1505 Contents lists available at ScienceDirect Marine Pollution Bulletin journal homepage: www.elsevier.com/locate/marpolbul