Integration of sediment contamination with multi–biomarker responses in a novel bioindicator candidate (Sepia officinalis) for risk assessment in impacted estuaries

Abstract

The Sado estuary (SW Portugal) is an example of the type of pressures coastal areas are subjected to, encompassing fisheries, agriculture, industries and other human activities, most of which may act as sources of aquatic pollution. In order to assess the impact of aquatic contaminants onto the biota, biomonitoring is compelling and the search for suitable bioindicator organisms is mandatory. The common cuttlefish, Sepia officinalis, is a very important species to fisheries, especially in the Sado estuary, albeit yet unsurveyed in ecotoxicological studies. For the purposes of biomonitoring, cuttlefish were collected from two different sites in the Sado estuary and from an external reference area. Additionally, environmental contamination was determined from sediment samples. Sediments were characterized for granulometric fractions, total organic matter, redox potential and for the levels of metals (Cr, Ni, Cu, Zn, Cd and Pb), metalloids (As and Se), polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and the pesticides dichloro diphenyl trichloethane plus its main metabolites (DDTs) and hexoclorobenzene (HCB). A multi–biomarker approach was applied in two organs, digestive gland and gills, through the analysis of lipid peroxidation, total glutathione, the reduced/oxidised glutathione ratio, glutathione S–transferase activity and induction of metallothionein–like proteins. The results showed that the Sado estuary is especially contaminated by metals when compared to the reference area. In addition, even within the Sado estuary, considerable heterogeneity exists regarding sediment contamination. The biomarker responses, especially in the digestive gland, were overall consistent with sediment contamination. This relationship was less obvious in the gills, reflecting, nevertheless, high sensibility to environmental pressures. Thus, S. officinalis revealed to be a good species to address environmental contamination and likely an adequate bioindicator in environmental risk assessment programs. The integration of all biomarker responses disclosed that the levels of contamination of the Sado estuary, although considered to be moderate, cause responses and adverse effects in organisms, from which it may be inferred that current management policies have not yet been able to eradicate pollution from this ecosystem.