Application of an integrated biomarker response index (IBR) to assess temporal variation of environmental quality in two Portuguese aquatic systems

Estuaries are extremely productive systems faced with great anthropogenic pressure, namely from contaminants of both metallic and organic nature which may affect the ecological quality of these systems. Moreover, it is known that contaminants fluctuate seasonally and this could influence the health status of organisms. In order to identify the most affected seasons and areas in two Portuguese aquatic systems with strong anthropogenic influences, a method that combines several biomarker responses into a general “stress index” denominated “integrated biomarker response” (IBR) was applied using the stress responses in the liver of common goby Pomatoschistus microps collected from two sites within both estuaries (Ria de Aveiro and Tagus). Parameters included in the IBR were the biomarkers superoxide dismutase (SOD), catalase (CAT), ethoxyresorufin-O-deethylation (EROD), glutathione s-transferase (GST), metallothioneins (MT), lipid peroxidation (LPO) and condition indices (RNA:DNA ratio and Fulton's condition factor K. Pollutant concentrations in the sediment (metals and PAHs) were also analyzed. Biomarkers in P. microps in Ria de Aveiro lagoon (sites A and B) showed distinct seasonal variation. In site A, IBR highlighted the spring as the season with highest biomarker responses, and RNA:DNA as the most contributing biomarker, while in site B the most impacted season was the summer, associated to the responses of MT and antioxidant enzymes (CAT and SOD), probably as a result of levels of Hg in the sediments. In both sites within the Tagus estuary (C and D) the IBR showed that biomarker responses were higher in autumn, with CAT, EROD, GST and LPO as the most altered biomarkers. In this season the levels of PAHs, Pb and Cr were the highest. Overall, the IBR index provides an integrated approach for assessing the health status of organisms and to identify temporal patterns of contamination.