Figure 4 is a map of Canada with a square over the Great Lakes region (enlarged to provide a more refined view of that area). The left vertical axis shows the atmospheric deposition and terrestrial mercury load in micrograms of mercury per square metre per year (mg m-2 yr-1). Several lakes in western (and one in eastern) Northwest Territories are above the estimated lowest observed adverse effect level for fish toxicity, while the remainder fall below these levels. Are Canadian ecosystems responding to recent reductions in domestic atmospheric emissions of mercury? Methylation of mercury is determined by how much mercury is available to methylating micro-organisms and how efficiently the micro-organisms can convert mercury to methylmercury. Mercury is emitted naturally from soils to the air. Key findings, as detailed in the reviews, relate to sources and long-range transport of mercury to the Canadian Arctic, its cycling within marine, freshwater, and terrestrial environments, and its bioaccumulation in, and effects on, the biota that live there. Levels of mercury over the last 40 years have increased in 31% of Canadian wildlife populations studied, decreased in 21%, and remained stable in 48%. Ecotoxicology 20, 1512-1519. How might changes in other human activities (e.g., land-use practices) affect the distribution of mercury between environmental compartments, methylmercury formation, and the accumulation in biota? Figure 1: Simplified schematic of biomagnification (left) and bioaccumulation (right) processes of methylmercury in the ecosystem. The Summary of Key Results contains the most significant scientific results, recommendations for future work, and answers to policy-relevant science questions. Marine animals are important dietary items that expose many Canadians who rely on them as a major food source to methylmercury. The levels of mercury reported in the Thick-Billed Murre eggs (green circles) range between 0.5 and 1.5 mg g-1 dry weight over the whole sampling period. The air is the first place to identify changes in emissions of mercury. If not, what factors are confounding/masking the expectation of recovery? Mercury can remain in the air for a long time (6-12 months) and can be transported long distances from its source, termed long-range transport. Canada has identified mercury and its compounds as a toxic substance under the Canadian Environmental Protection Act, (1999). National-scale investigations, such as a Canada-wide fish survey for mercury are a valuable indicator of recovery. The Canadian Mercury Science Assessment presents science conducted under the Clean Air Regulatory Agenda (CARA) Mercury Science Program, led by Environment Canada, and the Northern Contaminants Program (NCP), led by Aboriginal Affairs and Northern Development Canada as well as scientific work funded by Health Canada, Natural Resources Canada, Fisheries and Oceans Canada, provincial and … However, root uptake of mercury by forest vegetation and transfer of this mercury into wood is low. Fish and wildlife populations that are at risk would likely benefit from further reductions in industrial mercury emissions, which would decrease the deposition of new mercury available for methylation and bioaccumulation. This assessment further identifies key gaps in our understanding of how mercury travels, where it ends up, the impact of human activities and changes in mercury pollution. The levels in organisms living in most highly eutrophic systems are low, but moderate eutrophic conditions are responsible for higher rates of mercury methylation and uptake by aquatic organisms that can last for several decades. Green bars represent fish sampled from contaminated lakes (i.e., lakes categorized as likely receiving some level of mercury pollution from nearby sources). The contributions of other minor sectors are expected to increase due to population growth and increased demand for materials. Methylmercury is found in seawater at ultra-low levels; however, its biomagnification through long food chains in the marine environment can result in elevated concentrations in predatory fish, mammals, and seabirds. There remain insufficient monitoring data to expand the scale of information about mercury trends and predictions across the country. The Canadian Mercury Science Assessment is a comprehensive, peer-reviewed synthesis of the state of scientific knowledge on mercury in Canada that includes information from the NCP report, covering Canada south and north of the Arctic Circle. In planning land uses that can increase mercury levels in waterways, special emphasis should be placed on the lakes and rivers most frequently used for fishing and hunting, including even occasional sport fishing, food sources for native communities, and subsistence hunting. The lower map shows all sites active from 1995 to 2014 and further identifies precipitation and TGM sites run by the Canadian Air and Precipitation Monitoring Network (CAPMoN), which uses the yellow and orange colours from the upper map, speciation sites operated under CARA (green) and other sites, which are shown as pink for precipitation, purple for TGM and brown for speciation. In terms of risk, certain populations of wildlife and humans are more vulnerable than others to mercury exposure. Circular arrows close to the land and lake beside the moose, goose and loon refer to Chapter 12: “Health Effects of Mercury in Fish and Wildlife in Canada” and Chapter 13: “Assessment of Current Mercury Risks to Piscivorous Fish and Wildlife in Canada.” The information contained in Chapter 14: “Mercury and Human Health” is indicated next to the two humans in the image. This chapter presents knowledge of mercury exposure of Canadians, studies of human health effects, and measures for risk management. The Government of Canada’s actions to manage risks associated with mercury are summarized in the Risk Management Strategy for Mercury.Note de bas de page3 Canada has signed the United Nations Environment Programme’s Minamata Convention on Mercury (October 2013), which has as its primary goal the protection of human health and the environment from anthropogenic emissions and releases of mercury and mercury compounds. Climate influence on mercury in Arctic seabirds. For wildlife, top predators, particularly those associated with aquatic food chains, are at greatest risk from high dietary exposure to mercury because they accumulate mercury from their prey, which can lead to high levels over their lifetimes (biomagnification). Environment Canada and Health Canada, Ottawa. For terrestrial systems, there are no long-term records for observed mercury levels in streams, which are required to estimate their recovery time scale. The left pie chart shows the industrial sector contribution to air in Canada in 2010. As well, capacity to predict the effect of changes in anthropogenic emissions on fish mercury concentrations at a national scale is impeded by a lack of information on the physical characteristics of individual watersheds and the hydrodynamics of these watersheds across Canada. The remainder of the source regions have terrestrial sources contributing more than anthropogenic sources to mercury deposited in Canada. New reservoirs result in large areas of terrestrial vegetation being flooded, leading to decomposition of the vegetation and stimulation of microbial activity, including bacteria that methylate mercury. The lower pH and higher concentrations of metals found in acidic waters increase the uptake of toxic metals in biota, affecting the growth, survival, and reproduction of fish, invertebrates, and primary producers and pose a major threat to aquatic biodiversity. While several Arctic and global assessments specifically related to mercury over the past 10 years have identified this metal as an important environmental and health issue, the Canadian Mercury Science Assessment, which includes up-to-date information on mercury in Canada as a whole, is the first comprehensive evaluation of mercury in the Canadian environment. Analysis of teeth has shown that mercury levels in marine biota increased after the late 19th century, with the most substantial increases occurring in the mid-20th century. For instance, current evidence shows that mercury levels are going up in some populations of Arctic biota but not necessarily in others, which suggests local or regional factors that may involve climate change. The dashed line with an arrow represents the passage of time from a young small fish to a larger older fish. Mercury levels in Canada are not driven solely by domestic emission of mercury. Technology & Science Mercury, ... bear populations at high risk of suffering effects from mercury. Finally, mussels in the Maritimes show a decreasing trend in mercury concentration levels over time. In Canada, there are a substantial number of aquatic environments in which mercury levels in fish-eating (piscivorous) fish and wildlife are sufficiently high to be of concern. Is mercury a risk to ecosystem and human health in Canada? Efforts in the last 20 years have greatly improved our understanding of the sources, transport, fate, and effects of mercury in the Canadian environment. Mercury levels in stream and lake sediments vary across Canada by region and from one location to another. Although Canadian, North American, and European anthropogenic emissions have declined in the past decades, recent inventories (2010) suggest that global emissions remained the same or were slightly higher than in 2005, reflecting greater emissions abroad, particularly from Asia. In Canada, methylmercury remains a potential public health issue for populations who rely on the consumption of large predatory fish and traditional wildlife items. Chapter 10: “Mercury in Terrestrial and Aquatic Biota Across Canada: Geographic Variation” and Chapter 11: “Mercury in Terrestrial and Aquatic Biota Across Canada: Temporal Variation” are both shown on the land surface. It has been shown that the acidity of the lake water is one of the most significant factors affecting mercury levels in fish. The horizontal (x) axis shows the year from 1990 to 2034. As well, eutrophication driven by agriculture and aquaculture can cause nutrient enrichment and increase the methylation potential of a given ecosystem. The Canadian Mercury Science Assessment presents science conducted under the Clean Air Regulatory Agenda (CARA) Mercury Science Program, led by Environment Canada, and the Northern Contaminants Program (NCP), led by Aboriginal Affairs and Northern Development Canada as well as scientific work funded by Health Canada, Natural Resources Canada, Fisheries and Oceans Canada, provincial and territorial governments, the Natural Sciences and Engineering Research Council, International Polar Year, and industry. Regions with approximately equal contribution from anthropogenic (dark) and other terrestrial (light) sources are Europe, USA, South Asia and Central Asia. Methylmercury is the most toxic form and is the predominant form in fish, wildlife, and humans. The red dashed line stays at approximately 8 mg m-2 yr-1  from 2007 to 2156. Ecotoxicology 20, 1487-1499. A warming climate, as well as changes in sunlight, in the amount of organic matter, in precipitation patterns, and in the frequency and intensity of forest fires will change the dynamics of the ecosystem and food webs. Of all the populations that report increases, 83% are from the Arctic and the greatest increases have been seen in seabirds. Each of these indicators provides a different aspect of understanding mercury issues in the Canadian environment. Canadian Mercury Science Assessment – Summary of Key Results which includes up-to-date information on mercury in Canada as a whole, is the first comprehensive evaluation of mercury in the Canadian environment. Canadian air emissions are small in comparison with those from other major mercury-emitting countries (for example, approximately 35% of US levels in 2008 and 1% of levels in China in 2010). Figure 6 shows the mercury levels in lake trout that have been sampled from numerous lakes across Canada. However, omega-3 fatty acids, found in high levels in some fish species, play a pivotal role in certain aspects of neurodevelopment, and may be capable of mitigating or negating some of the adverse effects of prenatal exposure to methylmercury through fish consumption. One way to assess the recovery of aquatic systems is to measure changes of mercury levels in piscivorous fish and wildlife species. Increasing mercury concentrations, seen in some populations, may be cause for concern (seabirds from Prince Leopold and Coats Island, burbot from Fort Good Hope, and burbot and lake trout from Great Slave Lake). The integrated ecosystem model simulated the relationships among mercury emissions, atmospheric cycling and deposition, export to lakes from land, mercury cycling within lakes, and bioaccumulation in fish. Figure 10 shows that mercury levels in Arctic seabirds have increased overall by 54% to 119% in the eggs of black-legged kittiwakes, northern fulmars, and the thick-billed murres over 35 years. Other TGM sites are at Little Fox Lake, Yukon; Reifel Island (inactive), Ucluelet and Whistler, British Columbia; Fort Chipewyan, Meadows, Genesee, Crossfield, Esther (all inactive) and Patricia McInnes, Alberta; Flin Flon, Manitoba; Burnt Island, Lake Ontario, Point Petre (all inactive) and Windsor, Ontario; Kuujjuarapik (inactive), Mingan and St. Anicet, Quebec; St. Andrews (inactive), New Brunswick; Southampton (inactive), Prince Edward Island; Alert, Nunavut. Preparation of this assessment began in 2008 with a series of workshops involving scientists and policy-makers from the federal, provincial, and territorial governments and from universities. Figure 7 is a graph of both the historical and projected amounts of mercury emitted in Canada. Reservoirs are bodies of water created by humans, including flooded areas, primarily for hydroelectric power generation and, to a lesser extent, flood protection, irrigation, water supply, and recreation. By contrast, Inuit in the eastern Canadian Arctic have shown the highest concentrations of mercury among northern populations, with levels exceeding 8 µg L-1 in over 50% of mothers examined during a small study in the Baffin region of Nunavut in 1997; however, more recent data suggest that northern levels have been decreasing in the last several decades. The results indicated potential risk to common loon behaviour in 36% of the study lakes and to reproduction in 10%. Finally, at the top left, a human being depicts the highest trophic level as well as the highest mercury level, as indicated by the brown arrow. The first CARA Mercury Science Program conducted research on biota at the 4 sites shown in Figure 14. Inorganic mercury concentrations in sediments may require decades to fully equilibrate, whereas the water column can respond within months. The small young fish has a yellow colouring which represents low mercury levels in fish when they are young, but as the fish becomes bigger (ages) it consumes more mercury, and the levels increase with time, size and age. Mercury from mining is generally released in an insoluble inorganic form, and certain aquatic conditions are required for the mercury to be methylated. As well, levels of mercury in fish are frequently elevated in rivers and lakes downstream of new reservoirs. In Lakes Superior, Huron, and Ontario, mercury levels in fish have declined an average 60% (in lake trout) and 67% (in walleye) from the 1970s to 2007. The dashed red, green and blue coloured lines branch off from the solid lines from 2007 onwards. Until its closure in 2009, Canada’s largest source of mercury to the atmosphere was the Hudson Bay Mining and Smelting operations in Flin Flon, Manitoba. The blue dashed line increases more rapidly than the solid line after 2007 to approximately 0.7 mg g-1 wet muscle in 2156, though it appears to be levelling off by then. Top: Wabamun Lake, Alberta (close to mercury emissions from coal-fired power plants); bottom: Lake 240, Experimental Lakes Area, Ontario (remote lake). Vancouver and Vancouver Island area primarily show teal, green, yellow and dark blue. As an example, the relative size of emission source contributions from 9 continental regions to deposition in 4 selected sub-regions in Canada is shown in Figure 8. In 2010, Environment Canada and Health Canada developed a Risk Management Strategy for Mercury that provides a comprehensive and consolidated description of the Government of Canada’s actions to manage risks associated with mercury. In 2005, approximately 115 t of mercury was deposited to Canada; approximately 40% of the mercury deposited was from current global anthropogenic emissions and approximately 60% from other global terrestrial (approximately 35%) and oceanic (approximately 25%) emissions. However, measured mercury levels in the ambient air have decreased, on average. In addition, mercury concentrations in precipitation have declined at most sites in Canada since the mid-1990s. Contributions from over 230 researchers are included in this assessment. A strong, coordinated, national leadership that engages partners from all aspects of wildlife management, research, and use will be the key to the success of this initiative. Figure 5 consists of 2 pie charts describing the contribution of the major industrial sectors to mercury emissions in Canada. Some of these gaps are as follows: Several recommendations from this assessment report are as follows: A detailed summary of the gaps of knowledge and recommendations for future research can be found in Chapter 15. Regions that are projected to be warmer and experience increased precipitation, runoff, and soil moisture levels would likely experience increased mercury loading from the atmosphere and terrestrial systems. All lines start within this shaded area on both graphs, rise to a maximum above the range, then taper off. The assessment is the outcome of a partnership between the Clean Air Regulatory Agenda (CARA) Mercury Science Program, led by Environment Canada, and the Canadian Arctic Northern Contaminants Program (NCP), led by Aboriginal Affairs and Northern … If so, what are the indicators of recovery, where is it occurring, and how quickly are ecosystems responding? 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