Over the last two decades, fish with elevated concentrations of mercury (Hg) have been observed in remote lakes, including the Adirondack region of New York. Studies across eastern North America have shown that fish Hg concentrations increase with decreases in lake pH. Recent controls in emissions of sulfur dioxide have resulted in some improvement in the acid-base status of Adirondack lakes. In addition, decreases in atmospheric Hg deposition have also occurred. In 1992-93 a survey of 25 lakes in the Adirondacks, representing diverse watershed and geochemical characteristics, was conducted to analyze patterns of Hg in the water column and yellow perch. The same 25 lakes were resurveyed in 2005-06 to evaluate if changes in lake concentrations of Hg species or fish Hg have occurred. Changes in water chemistry and fish Hg concentrations varied by lake. In general, pH and acid neutralizing capacity levels were greater, while sulfate concentrations were lower compared to the 1992-93 survey. Both total Hg (HgT) and methyl Hg concentrations have decreased in almost all of the lakes since 1992-93. In both the original and most recent survey, concentrations of HgT in perch increased with age, length, and weight. The decline in Hg fish tissue across age classes of yellow perch was lake dependent, with 8 lakes showing decreases in concentration and 11 lakes exhibiting no change. These data suggests that some lakes have responded to decreases in SO2 and/or Hg emissions over the past decade.
