Mercury contamination in the Laurentian Great Lakes region: introduction and overview.

The Laurentian Great Lakes region of North America contains substantial aquatic resources and mercury-contaminated landscapes, fish, and wildlife. This special issue emanated from a bi-national synthesis of data from monitoring programs and case studies of mercury in the region, here defined as including the Great Lakes, the eight U.S. states bordering the Great Lakes, the province of Ontario, and Lake Champlain. We provide a retrospective overview of the regional mercury problem and summarize new findings from the synthesis papers and case studies that follow. Papers in this issue examine the chronology of mercury accumulation in lakes, the importance of wet and dry atmospheric deposition and evasion to regional mercury budgets, the influence of land-water linkages on mercury contamination of surface waters, the bioaccumulation of methylmercury in aquatic foods webs; and ecological and health risks associated with methylmercury in a regionally important prey fish.

Mercury in the Great Lakes region: bioaccumulation, spatiotemporal patterns, ecological risks, and policy.

This special issue examines bioaccumulation and risks of methylmercury in food webs, fish and wildlife in the Laurentian Great Lakes region of North America, and explores mercury policy in the region and elsewhere in the United States and Canada. A total of 35 papers emanated from a bi-national synthesis of multi-media data from monitoring programs and research investigations on mercury in aquatic and terrestrial biota, a 3-year effort involving more than 170 scientists and decision-makers from 55 different universities, non-governmental organizations, and governmental agencies. Over 290,000 fish mercury data points were compiled from monitoring programs and research investigations. The findings from this scientific synthesis indicate that (1) mercury remains a pollutant of major concern in the Great Lakes region, (2) that the scope and intensity of the problem is greater than previously recognized and (3) that after decades of declining mercury levels in fish and wildlife concentrations are now increasing in some species and areas. While the reasons behind these shifting trends require further study, they also underscore the need to identify information gaps and expand monitoring efforts to better track progress. This will be particularly important as new pollution prevention measures are implemented, as global sources increase, and as the region faces changing environmental conditions.

The Canadian Clean Air Regulatory Agenda Mercury Science Program.

The Clean Air Regulatory Agenda (CARA) Mercury Science Program was developed to provide scientific information to support regulatory activities and accountability pertaining to atmospheric emissions of mercury in Canada. The first phase of the science program, entitled "Setting-the-Baseline", sought to achieve the following: identify key indicators of the state-of-the-Canadian environment with respect to the transport, fate and effects of mercury; define these indicators; and, understand the processes that relate these indicators to anthropogenic emissions of mercury. To achieve these outcomes, a consultative process was used to identify the scientific needs of the agenda for mercury; understand Canada's scientific capacity; and, develop a plan to fulfill these scientific needs. The science plan that emerged from this process was structured around the themes of atmospheric monitoring, landscape-based risk assessment, ecological risk assessment, ecosystem modeling, and trends. Implementation of the science plan necessitated a multi-disciplinary and extensively partnered program. To date, the CARA Mercury Science Program is producing coordinated science at the national-scale that aims to directly assess the effectiveness of the CARA for mercury and for many of Canada's other mercury-related policies.

A comparison of the transport and fate of polychlorinated biphenyl congeners in three Great Lakes food webs.

A food web bioaccumulation model was used to compare transport and fate of polychorinated biphenyls (PCB) congeners in three food webs in the Laurentian Great Lakes of North America. The model was used to quantify the contribution of sediment-derived and freely dissolved PCBs to the body burden of aquatic biota. In eastern Lake Erie (OH, USA), almost 100% of the chemical body burden of biota originates from sediment. In western Lake Erie, benthic invertebrates accumulated slightly more than half of their PCB body burden from sediment while fish accumulated less than half of their chemical body burden from sediment. Fish from Lake Ontario, Canada, accumulated less than 30% of their body burden of PCB congeners with log Kow < 6.4 from sediment and approximately half of their body burden of PCB congeners with log Kow > or = 6.4 from sediment. Field data and the model were also used to determine the effects of declining concentrations of PCBs in water and sediment on concentrations of PCBs in aquatic biota. Results indicate that, as concentrations of PCB congeners in the ecosystem decline, the role of sediment as the source of contaminant to aquatic biota increases. Furthermore, as sediment becomes the predominant source of contaminant to aquatic biota. the concentration of PCB congeners in biota tends to equilibrium with bottom sediment.