Molecular and biochemical biomarkers in environmental monitoring: a study with a benthic fish living in the Venice Lagoon

Introduction. The Venice Lagoon (VEL) is a coastal ecosystem known to be heavily contaminated (Locatello, 2009). In the present study, the effects of persistent organic pollutants on the aryl hydrocarbon receptor (AhR) and cytochrome P450 1A (CYP1A) expression and catalytic activity (ethoxyresorufin O-deethylase, EROD) were measured in situ by using Zosterisessor ophiocephalus, a benthic species living in the VEL and showing a resident behaviour. Materials and Methods. Fishes were sampled during spring and autumn seasons from three VEL areas (Porto Marghera, Val di Brenta and Porto Canale) with a high, intermediate or low level of contamination, respectively. A total of 189 pools, each one consisting of the liver of three animals, were prepared. Total RNA was extracted and liver microsomes obtained by using common procedures. Species-specific AhR, CYP1A and \u3b2-actin (reference gene) coding sequences were identified and sequenced. Aryl hydrocarbon receptor and CYP1A mRNA levels as well as CYP1A apoprotein and EROD were measured by using a quantitative Real Time RT-PCR approach, immunoblotting and a HPLC method, respectively. Confirmatory residue analyses (non-dioxin-like and dioxin-like polychlorinated biphenyls) were executed on the lipid component of pooled muscle by gas-chromatography. Results. When compared to Porto Canale, significant increases of CYP1A expression and EROD were noticed in samples from Porto Marghera and Val di Brenta. Data from residues analysis mirrored this trend to induction. Furthermore, season-differences were observed for CYP1A expression (higher in the spring, which represents the reproductive season) and EROD activity (higher in the autumn season). Contrasting results were obtained for AhR gene expression. Conclusions. This integrated biomarker approach confirmed Porto Marghera as the most polluted area of VEL (Zonta, 2007). Collectively, CYP1A expression was proved as a suitable biomarker of effect in Zoosterisessor ophiocephalus; therefore, this species may, in turn, be considered as a good sentinel species for VEL environmental monitoring in situ. Less clear-cut results were obtained for EROD. Present AhR data need further molecular investigations, also in light of its role in other physiological mechanisms, including reproduction (Cal\uf2, 2010). References. Locatello L., Matozzo V., Marin M. G., 2009. Biomarker responses in the crab Carcinus aestuarii to assess environmental pollution in the Lagoon of Venice (Italy). Ecotoxicology, 18:869-877. Zonta R., Botter M., Cassin D., Pini R., Scattolin M., Zaggia L. 2007. Sediment chemical contamination of a shallow water close to the industrial zone of Porto Marghera (Venice Lagoon, Italy). Marine Pollution Bulletin, 55:529-542. Cal\uf2 M., Alberghina D., Bitto A., Lauriano E.R., Lo Cascio P. 2010. Estrogenic followed by anti-estrogenic effects of PCBs exposure in juvenil fish (Sparus aurata). Food and Chemical Toxicology 48:2458-2463. Acknowledgements. Project supported by grants from Regione del Veneto (Dgr. 3094 03/10/2006) to M.D. and F.M. and Universit\ue0 degli Studi di Padova (60A08\u20104049/11) to M.G