A multibiomarker approach to assess environmental pollution in the Lagoon of Venice (Italy). II: the crab Carcinus aestuarii as sentinel species.

The multibiomarker approach is nowadays deemed the most suitable strategy in biomonitoring studies, better enabling the assessment of the effects of mixtures of contaminants in aquatic environments. In the present study three biomarkers were evaluated in male crabs Carcinus aestuarii collected in November 2007 in 4 sites of the Lagoon of Venice: Valle di Brenta and Cà Roman, located in the southern lagoon basin, Marghera and Palude del Monte, in the northern one. Acetylcholinesterase (AChE) activity (in gills and haemolymph), as a biomarker of exposure to neurotoxic compounds, vitellogenin (Vg)-like protein levels (in digestive gland, haemolymph and gonads), as a biomarker of exposure to estrogenic compounds, and ethoxyresorufin O-deethylase (EROD) activity (in digestive gland), as a biomarker of exoposure to several planar compounds such as polycyclic aromatic hydrocarbons (PAHs) and dioxin-like polychlorinated biphenyls (PCBs), were measured. The results showed significantly lower AChE activity in the haemolymph of crabs from Marghera, near the industrial area of Porto Marghera, and from Palude del Monte, used as a licensed area for clam culture. This suggests an exposure of animals to neurotoxic compounds originating from industrial effluents and from the urban area of the proximate city of Venice. Moreover, it has to be noted that Palude del Monte is located not far from a riverine outlet, possibly conveying agricultural wastewaters. Conversely, significantly higher AChE activity values were observed at Valle di Brenta, in the southern Lagoon. The same pattern of AChE activity was observed in crab gills, although significant differences among sites were not detected. Significantly higher levels of Vg-like proteins were recorded in the digestive gland and haemolymph of crabs collected at Palude del Monte. The lowest values were observed in digestive glands of crabs from Cà Roman, next to the lagoon inlet, and in haemolymph of crabs from Valle di Brenta, close to mainland. Higher EROD activity, although not significantly different, was observed in digestive glands of crabs from Cà Roman, where intense fishing and ship traffic occur. Since for all biomarkers no significant difference between Valle di Brenta and Cà Roman was found, data from both sites were pooled together and compared with those, similarly pooled, from the northern sites of Marghera and Palude del Monte. Interestingly, this comparison showed a significantly better condition for the southern basin if referring to Vg-like protein level and AChE activity, while a better condition was observed for the northern basin in relation to EROD activity. In the interpretation of this last result, the extremely high variability of EROD activity in crabs from the northern sites, compared to the more homogeneous situation for the southern sites, needs to be taken into account. Certainly, further investigation is required to check for this variability. In conclusion, considering all the results obtained, similar pollution levels in the monitored sites are suggested, despite the differences observed between northern and southern basin in relation to each specific biomarker, thus reflecting different conditions of anthropogenic impact. When comparing the biomarker responses in crabs and clams (see Matozzo et al., this Congress), indications can be gathered for using crabs, mobile and mainly carnivorous organisms, as sentinels for wider geographical areas in biomonitoring studies.