Biomarker responses in the clam Ruditapes philippinarum and contamination levels in sediments from seaward and landward sites in the Lagoon of Venice

A multibiomarker approach was used to assess effects of different environmental conditions in the clam Ruditapes philippinarum. Bivalves were monthly collected from March 2009 to February 2010 in two sites of the Lagoon of Venice differently influenced by both anthropogenic impact and natural conditions: a seaward site (Punta Sabbioni, PS), close to the Lagoon inlet of Lido, characterised by high hydrodynamism and influenced by intense passage of ships, and a landward site (Canale Dese, CD) characterised by low hydrodynamism and influenced by both riverine inputs and agricultural waste waters. Various biomarkers were measured at cellular, tissue and organism level: total haemocyte count, pinocytotic and haemolymph lysozyme activities, gill acetylcholinesterase activity (AChE), superoxide dismutase and catalase activities in both gills and digestive gland, condition index and survival-in-air. Water temperature, pH and salinity values and total chlorophyll concentrations were measured. In addition, grain size, organic matter content, and concentrations of p,p -DDT (dichlorodiphenyltrichloroethane) and its 5 homologues, 4 HCHs (hexachlorocyclohexanes), 13 PBDEs (polybrominated diphenyl ethers), 13 PCBs (polychlorinated biphenyls) and 18 PAHs (polycyclic aromatic hydrocarbons) were seasonally measured in surface sediments of the two sampling sites. Immunomarkers, as well as AChE activity, highlighted an overall better condition for clams from PS, whereas a different response was provided by the biomarkers measured at organism level, condition index increasing and survival-in-air decreasing in PS clams. No marked differences in sediment contamination levels (except for PAHs) were observed between CD and PS. Overall, results obtained demonstrated that biomarkers measured allowed to discriminate the two sampling sites. Considering that the contamination levels of sediments were similar between the two sampling sites, influence of abiotic factors cannot be excluded in influencing biological responses measured in clams.