Temporal and Spatial Trends in Freshwater Fish Tissue Mercury Concentrations Associated with Mercury Emissions Reductions

Abstract

Mercury (Hg) concentrations were monitored from 1999 to 2011 in largemouth bass (LMB) and yellow perch (YP) in 23 lakes in Massachusetts USA during a period of significant local and regional Hg emissions reductions. Average LMB tissue Hg concentration decreases of 44% were seen in 13 of 16 lakes in a regional Hg "hotspot" area. YP in all lakes sampled in this area decreased 43% after the major emissions reductions. Comparative decreases throughout the remainder of the state were 13% and 19% for LMB and YP respectively. Annual tissue mercury concentration rate decreases were 0.029 (LMB) and 0.016 mg Hg/kg/yr (YP) in the hotspot. In lakes around the rest of the state, LMB showed no trend and YP Hg decreased 0.0068 mg Hg/kg/yr. Mercury emissions from major point sources in the hotspot area decreased 98%, and 93% in the rest of the state from the early 1990s to 2008. The significant declines in fish Hg concentrations in many lakes occurred over the second half of a two decade decrease in Hg emissions primarily from municipal solid waste combustors and, secondarily, from other combustion point sources. In addition to the substantial Hg emissions reductions achieved in Massachusetts, further regional, national and global emissions reductions are needed for fish Hg levels to decrease below fish consumption advisory levels.

Modeling the global atmospheric transport and deposition of mercury to the Great Lakes

“…If this analysis is valid, then reductions in U.S. emissions since that time could contribute to reductions in atmospheric mercury in the region. Recent analyses have suggested that reductions in U.S. emissions have indeed led to observable, decreasing trends in environmental mercury concentrations at many sites in the Great Lakes and surrounding regions (Castro and Sherwell, 2015;Giang and Selin, 2016;Hutcheson et al, 2014;Sunderland et al, 2016;Weiss-Penzias et al, 2016;Zhang et al, 2016), lending credibility to the results presented here.…”

How closely do mercury trends in fish and other aquatic wildlife track those in the atmosphere? – Implications for evaluating the effectiveness of the Minamata Convention

“…Instead, mean fish Hg concentrations were found to be slightly higher in the period 2005-2010 than in 1974-1981, and were significantly so in northern pike. Such divergent results were also reported in fish Hg in four small lakes within a national park in northern Minnesota Science of the Total Environment xxx (xxxx) xxx-xxx (Brigham et al, 2014) and throughout the State of Massachusetts (Hutcheson et al, 2014) in the USA. Whereas the majority of these lakes showed a decreasing trend in fish Hg between~2000 and~2010, a smaller set of lakes showed an increasing or no trend.…”

Global and Local Impacts of Delayed Mercury Mitigation Efforts

“…These results are in line with those recently reported in Michigan’s Upper Peninsula 48 . Substantial and rapid response of fish contamination to reduced emissions have been observed near emissions sources 72–74 . However, the relatively lower policy impacts in remote areas (see Section 3.2) are likely to considerably prolong the time required to see substantial decreases in fish Hg concentrations.…”