Mercury trends in fish from rivers and lakes in the United States, 1969–2005

Abstract

A national dataset on concentrations of mercury in fish, compiled mainly from state and federal monitoring programs, was used to evaluate trends in mercury (Hg) in fish from US rivers and lakes. Trends were analyzed on data aggregated by site and by state, using samples of the same fish species and tissue type, and using fish (1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005) were compared to wet Hg deposition data from the Mercury Deposition Network (MDN) over the same period. Downward trends in Hg concentrations in fish from data collected during 1969-1987 exceeded upward trends by a ratio of 6 to 1. Declining Hg accumulation rates in sediment and peat cores reported by many studies during the 1970s and 1980s correspond with the period when the most downward trends in fish Hg concentrations occurred. Downward Hg trends in both sediment cores and fish were also consistent with the implementation of stricter regulatory controls of direct releases of Hg to the atmosphere and surface waters during the same period. The southeastern USA had more upward Hg trends in fish than other regions for both site and state aggregated data. Upward Hg trends in fish from the southeastern USA were associated with increases in wet deposition in the region and may be attributed to a greater influence of global atmospheric Hg emissions in the southeastern USA. No significant trends were found in 62% of the fish species from six states from 1996 to 2005. A lack of Hg trends in fish in the more recent data was consistent with the lack of trends in wet Hg deposition at MDN 176 Environ Monit Assess (2011) 175:175-191 sites and with relatively constant global emissions during the same time period. Although few significant trends were observed in the more recent Hg concentrations in fish, it is anticipated that Hg concentrations in fish will respond to changes in atmospheric Hg deposition, however, the magnitude and timing of the response is uncertain.

Spatiotemporal trends of mercury in walleye and largemouth bass from the Laurentian Great Lakes Region

“…The leveling off of the trend in Hg concentrations was observed for multiple species from Lake St. Clair . A U.S. national dataset of multiple fish species found some upward trends but overall the Hg trend was downward from 1969 to 2005 (Chalmers et al 2010).…”

Mercury temporal trends in top predator fish of the Laurentian Great Lakes

“…However, Hg concentrations have not always decreased with stricter regulations, raising new questions about ecosystem dynamics. Previous studies have found that in some instances, fish Hg concentrations are now exhibiting upward trends (Weis 2004;Monson 2009;Bhavsar et al 2010;Chalmers et al 2010).…”

Health and Environmental Risk Assessment Project for bottlenose dolphins Tursiops truncatus from the southeastern USA. II. Environmental aspects

“…THg concentrations in IRL dolphins decreased significantly between 2003 and 2012. Declines in the concentrations of Hg in US fish populations have also been reported in recent years (Chalmers et al 2011). These national declines have been attributed to reduced exposures from point sources and emissions, rather than to a decline in global atmospheric deposition.…”

“…These national declines have been attributed to reduced exposures from point sources and emissions, rather than to a decline in global atmospheric deposition. However, Hg contamination patterns in the southeastern USA show increases, reflecting hydro-geological factors that favor the deposition of Hg from the atmosphere, rather than emissions from local point sources (Chalmers et al 2011). There is very little industrial activity along the borders of the IRL.…”