Author's personal copy Incorporating bioavailability into management limits for copper in sediments contaminated by antifouling paint used in aquaculture Stuart L. Simpson a,⇑ , David A. Spadaro a , Dom O’Brien b a Centre for Environmental Contaminants Research, CSIRO Land and Water, Locked Bag 2007, Kirrawee, NSW 2232, Australia b Huon Aquaculture Group, PO Box 42, Dover, Tasmania 7117, Australia highlights  Low bioavailability of copper in antifouling paints.  Probability of chronic toxicity increases when bioavailable copper >65 mg kg 1 .  Guidelines based on dilute acid-extractable copper most effective.  Acid-volatile sulfide was ineffective as a SQG-modifying factor.  Zinc from fish feed is more bioavailable, but much less toxic, than the copper. article info Article history: Received 19 June 2013 Received in revised form 13 August 2013 Accepted 22 August 2013 Available online 27 September 2013 Keywords: Sediment quality guidelines Chronic toxicity Risk assessment Antifoulant Fish abstract Although now well embedded within many risk-based sediment quality guideline (SQG) frameworks, contaminant bioavailability is still often overlooked in assessment and management of contaminated sediments. To optimise management limits for metal contaminated sediments, we assess the appropri- ateness of a range methods for modifying SQGs based on bioavailability considerations. The impairment of reproduction of the amphipod, Melita plumulosa, and harpacticoid copepod, Nitocra spinipes, was assessed for sediments contaminated with copper from antifouling paint, located below aquaculture cages. The measurement of dilute acid-extractable copper (AE-Cu) was found to provide the most useful means for monitoring the risks posed by sediment copper and setting management limits. Acid-volatile sulfide was found to be ineffective as a SQG-modifying factor as these organisms live mostly at the more oxidised sediment water interface. SQGs normalised to %-silt/organic carbon were effective, but the ben- efits gained were too small to justify this approach. The effectiveness of SQGs based on AE-Cu was attrib- uted to a small portion of the total copper being present in potentially bioavailable forms (typically <10% of the total). Much of the non-bioavailable form of copper was likely present as paint flakes in the form of copper (I) oxide, the active ingredient of the antifoulant formulation. While the concentrations of paint- associated copper are very high in some sediments, as the transformation of this form of copper to AE-Cu appears slow, monitoring and management limits should assess the more bioavailable AE-Cu forms, and further efforts be made to limit the release of paint particles into the environment. Crown Copyright Ó 2013 Published by Elsevier Ltd. All rights reserved. 1. Introduction Antifouling paints are used on the hulls of boats and fish nets in the aquaculture industry to prevent biofouling, i.e. the growth and colonization of marine microorganisms (Yebra et al., 2004; Brai- thwaite et al., 2007). Since the phasing out of the use of tributyltin (TBT)-based paint products due to well recognised environmental harm, paints that utilise copper as the biocidal component, mainly in the form of copper (I) oxide, now dominate the market. Zinc is also a component of many paint formulations, and usually present as zinc oxide or pyrithione when used in antifouling paint formulations. While the benefits to industries from reducing biofouling are considerable, elevated concentrations of copper frequently occur in confined waters such as marinas (Schiff et al., 2007), and in sed- iments due to the abrasion of painted surfaces (Dean et al., 2007; Turner, 2010; Takahashi et al., 2012; Simpson et al., 2012a). Fish aquaculture also introduces metals into the aquatic environment through input of fish feed (Burridge et al., 2010). Zinc is an impor- tant nutrient for fish and the major source of the zinc in the aquaculture sediments will originate from fish food formulations, rather than the paint. While the organic waste components of unconsumed feed and fish faeces that settle beneath aquaculture 0045-6535/$ - see front matter Crown Copyright Ó 2013 Published by Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.chemosphere.2013.08.100 ⇑ Corresponding author. Tel.: +61 2 9710 6807. E-mail address: stuart.simpson@csiro.au (S.L. Simpson). Chemosphere 93 (2013) 2499–2506 Contents lists available at ScienceDirect Chemosphere journal homepage: www.elsevier.com/locate/chemosphere