Assessing a bioremediation strategy in a shallow coastal system affected by a fish farm culture – Application of GIS and shellfish dynamic models in the Rio San Pedro, SW Spain C. Silva a,b,c,⇑ , E. Yáñez c , M.L. Martín-Díaz a,b , T.A. DelValls a a UNITWIN/UNESCO/WiCoP, Physical Chemical Department, University of Cádiz, Polígono Río San Pedro s/n, 11510 Puerto Real, Cádiz, Spain b Andalusian Center of Marine Science and Technology (CACYTMAR), University of Cádiz, Polígono Río San Pedro s/n, 11510 Puerto Real, Cádiz, Spain c School of Marine Science, Pontificia Universidad Católica de Valparaíso, Avda, Altamirano 1480, Valparaíso, Chile article info Keywords: Integrated multi-trophic aquaculture Bioremediation Geographic information systems Carrying capacity Carbon and nitrogen mass balance Eutrophication abstract An integrated multi-trophic aquaculture assessment for Pacific oyster (Crassostrea gigas) aquaculture as a bioremediation strategy in areas impacted by fish farm effluents in Rio San Pedro was assessed by com- bining geographic information system with carrying capacity models. Sites of 0.44 km 2 were evaluated considering constraints; physical factors, growth and survival factors, environmental quality factors, water and sediment quality criteria, factor suitability ranges, and Multi-Criteria Evaluation. Isleta and Fla- menco are promising sites for oyster production, and Dorada is of marginal interest. Carbon and nitrogen removal from the water by algae and through detritus filtration was estimated. The biodeposition of organic material from longline leases was found to have little negative impact on sediment. The eutrophi- cation results indicate that phytoplankton removal had a positive impact on water quality at the Dorada. This case study quantified the direct profitability and bioremediative environmental service advantages that fish-shellfish farms can have relative to fish monocultures. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction Marine aquaculture continues to expand globally, with an aver- age annual increase in production of 5.4% in terms of quantity and 8.3% in value (FAO, 2009). However, marine fish aquaculture has a negative impact on the environment, such as sediment organic enrichment and eutrophication (Holmer et al., 2005; Islam, 2005; Kalantzi and Karakassis, 2006; Mantzavrakos et al., 2007); chemi- cal pollution from pharmaceuticals, organics, bactericides and metals (Antunes and Gil, 2004; Boxall, 2004; Cabello, 2006; Calvi et al., 2006; Hamilton et al., 2005; Hites et al., 2004; Holmstrom et al., 2003; Lai and Lin, 2009; Sapkota et al., 2008); and changes in the biodiversity of endemic populations (Pusceddu et al., 2007; Tomassetti and Porrello, 2005; Vezzulli et al., 2008). As an example, Rio San Pedro (RSP) is a salt marsh creek situ- ated in the SW of Spain and has traditionally been a highly produc- tive area for aquaculture and clam fishing. Untreated aquaculture waste waters from a fish farm in the upper part of the creek dis- charges directly into the coastal waters, constituting a major factor of pollution in the coastal ecosystem. Organic enrichment contam- ination is produced by the waste in dissolved and particulate form, and although most of the carbon fed to fish is converted into bio- mass, a considerable amount of unconsumed food and faeces set- tles out as sediment (Karakassis et al., 2002; Papageorgiou et al., 2009). The area affected by the organic enrichment of the fish farm effluent in the RSP is characterised by low pH and higher levels of nutrients, particulate organic matter, suspended solids, and metals (De la Paz et al., 2008b; Mendiguchía et al., 2006; Tovar et al., 2000a). Organic enrichment can change the physical and chemical composition of sediments (Karakassis et al., 2002), affecting the structure of the macrobenthic communities and the health status of the biota (Solan et al., 2004). The negative environmental impacts of fish-fed aquaculture can be mitigated through the incorporation of an Ecosystem Approach to Aquaculture (EAA – Aguilar-Manjarrez et al., 2010; Soto et al., 2008) into integrated coastal zone management (ICZM) plans. Applications of EAA include optimising site selection, the real-time management of aquaculture operations, estimating the aquacul- ture carrying capacity, evaluating the ecosystem resilience, and integrated multi-trophic aquaculture (IMTA) bioremediative ap- proaches promoting shellfish culture in conjunction with finfish aquaculture species (Aguilar-Manjarrez et al., 2010). The assess- ment of suitable IMTA sites, potential production, economic outputs, and environmental effects is essential to minimising envi- ronmental impacts and social conflicts and to maximising eco- nomic return (Buschmann et al., 2009; Ferreira et al., 2010; Nobre et al., 2010; Ridler et al., 2007b; Troell et al., 2009). 0025-326X/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved. doi:10.1016/j.marpolbul.2012.01.019 ⇑ Corresponding author at: UNITWIN/UNESCO/WiCoP, Physical Chemical Depart- ment, University of Cádiz, Polígono Río San Pedro s/n, 11510 Puerto Real, Cádiz, Spain. Tel.: +34 956016794; fax: +34 956016040. E-mail address: claudio.silva@uca.es (C. Silva). Marine Pollution Bulletin 64 (2012) 751–765 Contents lists available at SciVerse ScienceDirect Marine Pollution Bulletin journal homepage: www.elsevier.com/locate/marpolbul