Mediterranean fouling communities assimilate the organic matter derived from coastal fish farms as a new trophic resource D. Gonzalez-Silvera a,⇑ , D. Izquierdo-Gomez b , V. Fernandez-Gonzalez b , F.J. Martínez-López a , J.A. López-Jiménez a , P. Sanchez-Jerez b a Department of Physiology, Faculty of Biology, Regional Campus of International Excellence ‘‘Campus Mare Nostrum’’, University of Murcia, 30100 Murcia, Spain b Department of Marine Sciences and Applied Biology, University of Alicante, Spain article info Article history: Available online 7 January 2015 Keywords: Fatty acids Aquaculture wastes Fouling Benthic communities Terrestrial markers abstract Currently, the lipid content of fish feeds includes high amounts of terrestrial vegetable oils, rich in n-6 fatty acids and poor in n-3 fatty acids. Sinking organic matter in the shape of fragmented pellets and fish faeces could be ingested by the surrounding fauna attracted to the submerged structures of aquaculture facilities or living in natural benthic habitats. Fatty acids contained in feed pellets were used as trophic markers to shed light on the assimilation and incorporation of aquaculture wastes by the invertebrate fauna associated to sea-cages. Eighteen macroinvertebrate species, and zooplankton, seaweeds and sed- iments were collected from two fish farms, one of which (control) had not been used as such for two years. This study demonstrates that macroinvertebrate fauna present in fouling can take up sinking organic matter from farms. Further research should be directed at assessing the potential implications of aquaculture production for the surrounding ecosystem. Ó 2014 Elsevier Ltd. All rights reserved. 1. Introduction Anthropogenic perturbations in coastal marine ecosystems include the physical modification of habitats, the introduction of nutrients and pollutants, and alterations to populations of wild species as a result of fishing and other processes (Dempster et al., 2009). Fish farms have an ecological effect on the surround- ing environment, which is noticeable not only at a benthic level (e.g. Naylor et al., 2000; Karakassis et al., 2000; Black, 2001; Dempster et al., 2004), due to sinking organic matter in the form of uneaten feed pellets and faeces (Fernandez-Jover et al., 2009; Black et al., 2012). Changes in the invertebrate assemblage struc- ture (Fabi et al., 2009; Madin et al., 2009; Fernandez-Gonzalez et al., 2013) have been extensively studied in relation to the increase of organic matter sedimented from fish farms. Most farmed marine fish are piscivorous species that require marine ingredients in their feed in order to achieve an optimal growth rate and health status (Naylor et al., 2000; Sargent et al., 2002; Fernandez-Jover et al., 2011). Nevertheless, current feeds also include high levels of vegetable oils in their composition, such as linseed, soybean, rapeseed or palm oil that are rich in saturated fatty acids (SFA), monounsaturated fatty acids (MUFA) like oleic acid (18:1n-9, OA) and polyunsaturated fatty acids (PUFA) like linoleic acid (18:2n-6, LA) and a-linolenic acid (18:3n-3, LNA). Additionally, these vegetable oils present poor levels of the long chain PUFAs eicosapentaenoic acid (20:5n-3, EPA) and docosahexaenoic acid (22:6n-3, DHA), which are abundant in fish oils (Turchini et al., 2010; Fernandez-Jover et al., 2011) and become essential for fish, as well as arachidonic acid (20:4n-6, ARA). Large amounts of organic matter in the form of high energy fish feed rich in vegetable fatty acids are introduced into the environment, where uneaten pellets are consumed by wild fish which assemble near farms. In addition, fragmented pellets and faeces might represent a new trophic source for fouling organisms, providing them with a new source of terres- trial fatty acids such as LA and LNA, which are unusual in marine environments, and should be investigated (Sara et al., 2004; Fernandez-Jover et al., 2008; Arechavala-Lopez et al., 2011). If the above is true, it could modify their fatty acid composition; however, our knowledge of the extent to which the commercial feed affects different trophic levels is limited. It remains unclear which ecolog- ical compartments might be influenced by commercial feed enter- ing the food chain. Changes in the fatty acid profile of the aggregated fauna have been detected by several authors (Skog et al., 2003; Fernandez-Jover et al., 2007, 2009) but there is no full picture of the influence of fish farming on marine communities. http://dx.doi.org/10.1016/j.marpolbul.2014.12.029 0025-326X/Ó 2014 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. Tel.: +34 657635620. E-mail addresses: danielgs@um.es (D. Gonzalez-Silvera), david.izquierdo@ua.es (D. Izquierdo-Gomez), victoria.fernandez@ua.es (V. Fernandez-Gonzalez), javmar- aq@um.es (F.J. Martínez-López), joseang@um.es (J.A. López-Jiménez), psanchez@ua. es (P. Sanchez-Jerez). Marine Pollution Bulletin 91 (2015) 45–53 Contents lists available at ScienceDirect Marine Pollution Bulletin journal homepage: www.elsevier.com/locate/marpolbul