Impact of remobilized contaminants in Mytilus edulis during dredging operations in a harbour area: Bioaccumulation and biomarker responses Marta Martins a,b,n , Pedro M. Costa a , Joana Raimundo b , Carlos Vale b , Ana M. Ferreira b , Maria H. Costa a a IMAR-Instituto do Mar, Departamento de Ciˆ encias e Engenharia do Ambiente, Faculdade de Ciˆ encias e Tecnologia da Universidade Nova de Lisboa, 2829-516 Caparica, Portugal b IPMA-Instituto Portuguˆ es do Mar e da Atmosfera, Avenida de Brası ´lia, 1449-006 Lisboa, Portugal article info Article history: Received 27 April 2012 Received in revised form 16 July 2012 Accepted 2 August 2012 Available online 28 August 2012 Keywords: Dredging Sediment contamination Mussel Bioavailability Sediment Quality Guidelines abstract Dredging operations in harbours are recurrent to maintain accessibility and navigational depths. One of the main environmental risks of these operations is the remobilization of contaminants trapped in the sediments, rendering them more bioavailable to the biota. However, regulatory policies regarding the contamination risk of dredging chiefly apply to the disposal of dredged materials rather than the direct impact of the procedure itself. In order to assess the ecotoxicological risk of harbour dredging operations in a polluted estuary (the Tagus, W Portugal), the present study compared bioaccumulation and biomarker responses in field-deployed mussels before and after the beginning of operations, complemented by sediment characterization and risk analysis based on standardized sediment quality guidelines. The results revealed a very significant increase in genotoxicity and oxidative stress from the beginning of dredging onwards, which was accompanied by increased bioaccumulation of toxicants, especially polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs). Overall, the results indicate the importance of surveying the direct impacts of these procedures on local contamination, especially considering these sediments had been previously classified as ‘‘trace contaminated’’, according to normative guidelines, and therefore safe for disposal. This study shows the importance of obtaining both chemical and biological data in standard monitoring procedures and that the remobilization of contaminants by dredging operations may be grossly underestimated, which calls for caution when assessing the impact of these activities even in low to moderately polluted areas. & 2012 Elsevier Inc. All rights reserved. 1. Introduction The fate of dredged materials and the impact of dredging operations in harbours are acknowledged factors in coastal and estuarine environmental quality since sediments from impacted areas tend to store hazardous concentrations of organic and inorganic contaminants that may be desorbed following distur- bance, therefore promoting bioavailability and speciation to more toxic forms (Roberts, 2012). However, determining the ecotox- icological risk of aquatic sediments retains many acknowledged constraints, in particular those that relate to the likely presence of complex mixtures of contaminants, their possible within- organism interaction effects and to their intricate geochemical matrix (e.g., Costa et al., 2012). Therefore, researchers in the field recognize nowadays the need to enforce integrative approaches to determine the potential hazard of sediment-bound contaminants. The Weight-of-Evidence (WOE) approach, for instance, has been developed to provide a multidisciplinary characterization of environmental quality of sediments which combine different lines of evidence (LOEs), in essence integrating the levels of contamination to the ecological changes it may trigger (Chapman et al., 2002Chapman, 2007; Dagnino et al., 2008). Recent research suggest, after validation through modelling, that WOE approaches should indeed include key LOEs such as sediment chemistry, contaminant bioavailability, bioassays and biomarkers, the later including genotoxicity assessment (Piva et al., 2011; Benedetti et al., 2012). The WOE approach is a key of many Ecological Risk Assessment (ERA) strategies and is also in line with the updated European Water Framework (Directive 2008/105/EC) which requires member states to evaluate and classify the ecological status of water bodies integrating different quality indicators. Through the Oslo–Paris (OSPAR) convention, consensus guide- lines for the control of the disposal of dredged materials have already been proposed, being based on preceding sediment quality assessment approaches that take into account LOEs such as sediment chemistry, analysis of benthic communities and toxicity tests. Although the combination of multiple LOEs repre- sents an additional value to monitoring and management Contents lists available at SciVerse ScienceDirect journal homepage: www.elsevier.com/locate/ecoenv Ecotoxicology and Environmental Safety 0147-6513/$ - see front matter & 2012 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.ecoenv.2012.08.008 n Corresponding author at: Departamento de Ciˆ encias e Engenharia do Ambiente, IMAR-Instituto do Mar, Faculdade de Ciˆ encias e Tecnologia da, Uni- versidade Nova de Lisboa 2829-516 Caparica, Portugal. E-mail address: mmartins@ipimar.pt (M. Martins). Ecotoxicology and Environmental Safety 85 (2012) 96–103