Ethoxyresorufin O-deethylase (EROD) activity and fluctuating asymmetry (FA) in Zosterisessor ophiocephalus (Teleostei, Gobiidae) as indicators of environmental stress in the Venice lagoon

The impact of environmental stress on the grassgoby, Zosterisessor ophiocephalus, wasstudied at both biochemical and morphologicallevels, by comparing three sites in the Venicelagoon (the Northern, Central and Southernbasins) which differ in terms of the degree ofanthropogenic disturbance, in particular withregard to organic sediment contamination. At abiochemical level, the hepatic ethoxyresorufinO-deethylase (EROD) enzyme activity wasmeasured as a biomarker of the degree oforganic pollution (in particular regardingcontamination by PCBs and Dioxins). At amorphological level, the amount of fluctuatingasymmetry (FA) with regard to four bilateraltraits (postorbital length; otolith area;minimum otolith diameter; maximum and minimumotolith radii) was measured as a long termindicator of developmental stress. The ERODactivity was higher in grass gobies from theCentral basin, whereas the amount of FA washigher in the gobies collected from theNorthern basin. Both measurements indicatedthat the Southern basin was affected by lowlevels of environmental stress (low ERODinduction and a lower amount of FA). Theresults were discussed in the light of both theenvironmental differences among the threebasins and the different levels of biologicalorganisation at which the two indicators act.