An assessment of total and leachable contaminants in zebra mussels (Dreissena polymorpha) from Lake Erie.

Samples of zebra mussels, Dreissena polymorpha, from populations infesting two power generating stations on Lake Erie were subjected to tests assessing the potential for leaching of metals and other (inorganic and organic) contaminants from mussel waste destined for disposal in conventional landfills. These tests revealed that mussels collected from Ontario Hydro's Nanticoke Thermal Generating Station and Niagara Mohawk Power Corporation's Dunkirk Steam Station did not release hazardous materials in excess of limits set forth in Canadian and U.S. regulations, respectively. A variety of metals and inorganic materials leached from Nanticoke mussels at levels significantly lower than the registration limits for those analytes. Detectable levels of chloroform (0.080 mg/liter) and barium (3.3 mg/liter) leached from Dunkirk mussels at > 30-fold lower levels than U.S. regulatory action limits for those materials. Whole body analyses revealed a lack of detectable levels of herbicides and pesticides in either population with a variety of metals and inorganic constituents in all samples from both populations. The physiological condition of Dunkirk mussels appeared to be consistent with that of other Lake Erie populations based on percentage water and total fat content of soft tissues.

The Asiatic clam, Corbicula spp., as a biological monitor in freshwater environments.

Asiatic clams, Corbicula spp., are filter-feeding freshwater bivalves that are widely distributed, abundant, and fast growing with a lifespan of 1-3 yrs. A review of the existing literature demonstrates that Asiatic clams can concentrate organic pollutants from both water and sediment and heavy metals from water. In conjunction with these traits, they exhibit a high tolerance for the effects resulting from exposure to toxic substances. While an organism must possess these traits to serve as an effective biological monitor, they have also permitted the Asiatic clam to rapidly colonize natural and industrial environments resulting in purported ecological disturbances and severe economic repurcussions, respectively. Its invasive biofouling attributes therefore restrict the use of Asiatic clams for biomonitoring purposes from Corbicula-free drainage systems.

Tolerance of the Asiatic clam Corbicula spp. to lethal level of toxic stressors-a review.

Studies assessing the tolerance of the Asiatic clam, Corbicula spp., to a variety of chemical, environmental, and physical stressors are summarised and reviewed. A majority of the studies were conducted (1) in the laboratory, (2) with juvenile and adult stages and (3) with only one stressor per treatment. Trends in the data demonstrate that (1) equivalent median lethal concentrations were generated in studies using both static and flow-through techniques; (2) substantial increases in the levels of mortality among treated clams were obtained by extending exposure durations; (3) incorporation of recovery periods into experimental designs permitted the development of latent mortalities among treated clams; (4) tolerance among larvae was stage dependent while tolerance among adults was not; (5) higher levels of mortality were obtained when tests were conducted at higher temperatures; and (6) testing in the presence of substrate resulted in a decrease in the levels of mortality among treated clams. The implications of these findings are discussed in relation to efforts to mitigate the fouling effects of Asiatic clams in industrial cooling water systems by exposure to toxic chemicals.