Marine filters feeders ingest metals bound to dissolved and particulate matter in the water and the sediment. Bivalves are useful as bioindicators of pollution, as ingested metals can accumulate in both their soft tissues and calcium carbonate shells. The effects of experimental exposure to high levels of dissolved Fe on oxidative stress parameters in the respiratory tissues of the bivalve filter feeder Mya arenaria were investigated. Exposure to 500 μM dissolved Fe in the seawater resulted in a significant increase in total Fe and LIP (labile iron pool) content in the gills after 9 days. Both parameters remained elevated until day 17, the final day of exposure. Dichlorofluorescein diacetate oxidation rate of gill homogenates was significantly higher after 17 days of exposure to Fe overload, as compared to values in gills homogenates from control animals. Thiobarbituric acid reactive substances content increased by approximately 1.9-fold on day 9 and 3.7-fold on day 17 of treatment compared to non-exposed controls. Catalase activity was unchanged up to day 7 of Fe-exposure and decreased significantly on days 9 and 17 of treatment compared to controls. The content of nitrate and nitrite was unchanged during the initial 7 days of Fe exposure and decreased by 59% of the control values between days 9 and 17 of exposure. Similar effects were observed in mantle tissues, except for the antioxidant capacity. Catalase activity was not affected by the treatment. This study shows that the ability of tissues are specific, according to the features of the function in the overall survival of the organism, minimizing oxidative damage in molluscs exposed to excess dissolved Fe in seawater. DG was able to keep in average the same risk of efficient catalytically active actions of Fe even though the total amount of Fe in the tissue was significantly increased. A different capacity was observed either in gills or mantle where at day 17 the % of catalytically active Fe was increased by 2-folds when total Fe was drastically enhanced. Thus, the degree of protection seems as directly related to the higher metabolic activity in DG.