Assessment of Anodonta cygnea as a Biomonitor Agent for Copper and Zinc in Anzali Wetland, Iran

Background: Anzali wetland has been subjected to high levels of pollution due to contamination from several industrial sites in addition to agricultural chemicals. Mussels have been widely used for monitoring pollution in aquatic ecosystems, because they, as filter feeders, bioaccumulate pollutants. Therefore we decided to evaluate Anodonta cygnea for its application as a bio-monitor for copper (Cu) and zinc (Zn). Methods: A. cygnea specimens and their surface sediments were gathered from three locations in Anzali wetland. Afterwards, the collected samples (the soft tissues and shells of A. cygnea as well as surface sediments) were analyzed for Cu and Zn by a flame atomic absorption spectrophotometer (Model 670G). Results: The Cu and Zn concentrations in the sediments obtained from Anzali wetland were in the range of 21.05 to 25.53 for copper and 37.84 to 82.26 μg g-1 dw for zinc. The Cu and Zn levels in the soft tissue were 1.09-1.5 times and 5-7.3 times, respectively, higher than those of the shells. The CV values (%) in the soft tissues and shells were 36 and 53 for Cu, and 53.5 and 150.3 for Zn respectively. Conclusions: The lower Zn variability (CV) in the soft tissues of A. cygnea and significant correlation between Zn levels in the soft tissues of A. cygnea and the surface sediments indicated that the soft tissues of A. cygnea are more appropriate for bio-monitoring of Zn. Cu concentration in the sediment and Zn levels in the soft tissues were found to be comparatively higher than some of the international standards of reference.