The Baltic Sea is a unique semi-enclosed sea with a steady salinity gradient (5‰ to 30‰). Organisms have adapted to such low salinities, but are suspected to be more susceptible to stress. Within the frame of the integrated environmental monitoring BONUS+ project “BEAST” (Biological Effects of Anthropogenic Chemical Stress) the applicability of immune responses as salinity independent biomarkers for toxic effects in the blue mussel was investigated at 5 stations in the Danish Belt Sea (Baltic Sea) in autumn 2009. These stations were characterised by a salinity range (10.9 to 18.8‰) and different mixtures of pollutants (metals, PAHs and POPs), according to parallel chemical analysis of mussel tissues. The immune responses analysed included cellular components (total and differential haemocyte count, phagocytic activity and apoptosis) as well as cell-free factors (cytotoxic activity). Individuals from Frederiksværk (15‰; low metal but high PCB concentrations) showed significantly lower phagocytic activity compared to mussels from Roskilde Fjord (13‰, PAHs, mixture of metals: Cu, Pb, Hg, Cd, Ni) as well as a significantly higher number of circulating haemocytes with regard to organisms from Roskilde Fjord and Isefjord (18.8‰, high concentrations of HCHs, Hg and As). Both, phagocytic activity and total haemocyte count were shown to be influenced by Cu and PCBs, but not by salinity. Cytotoxic activities, in contrast, were dependent on salinity as well as HCH concentrations. Overall, salinity had an impact on the condition index of all individuals. However, haemocyte-mediated immunity was not affected. In conclusion, cellular immune responses were mainly influenced by pollutants, regardless to environmental salinities, whereas cell-free factors were impacted by both, salinity and pollution. Hence, cellular immune functions may be suitable as biomarkers in monitoring programmes for the Baltic Sea and other geographic regions with salinity variances of the studied range.
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Primo 16 - Pollutant Responses in Marine organisms, 2011