Developing a sentinel mollusc species for toxicity assessment: metal exposure, dose and response – laboratory v. field exposures and resident organisms

Abstract

Environmental contextMetal contamination in estuarine sediments can affect ecosystem health. Molluscs are commonly used as environmental indicators because they accumulate contaminants that cause adverse health effects. We investigated metal uptake and effects in the Sydney cockle, comparing exposure to contaminated lake sediments in situ and in laboratory aquariums. Although differences were observed between the different exposure types, all approaches were found to be valid for investigating metal health effects in this organism. AbstractRelationships between exposure, tissue dose and biological responses of the benthic marine bivalve Anadara trapezia to an estuarine sediment zinc, copper, lead, cadmium and selenium contamination gradient in Lake Macquarie, NSW, were evaluated using three approaches. Organisms were exposed to sediments in laboratory aquaria, caged in situ in the lake and lake resident organisms collected. Dose included total metal tissue burden and subcellular metal distribution to determine metabolically available metal. Response indices were total antioxidant capacity, lipid peroxidation, lysosomal stability and condition index. Bioaccumulation of total metals was higher in the laboratory and resident organisms than in those transplanted in the field but the contribution of individual metals to the total differed. Laboratory-exposed organisms had increased concentrations of cadmium and lead in their biologically active and detoxified metal fractions but not of the essential elements zinc and copper. Subcellular metal distribution patterns were the same in resident organisms but cadmium and lead burdens were higher in both fractions. Biomarker responses were similar in laboratory, transplanted and resident organisms. Total antioxidant capacity was significantly reduced and lipid peroxidation and lysosomal destabilisation significantly increased in all metal-exposed organisms compared with the reference A. trapezia. Condition index of laboratory-exposed organisms was significantly lower than in situ, resident and reference organisms. Clear metal exposure–dose–response relationships have been demonstrated for A. trapezia in laboratory and in situ experiments. Non-resident organisms, in both exposure scenarios, gave similar responses to resident metal-exposed organisms, showing all approaches are valid when investigating effects in this species.