Declining Aluminum Toxicity and the Role of Exposure Duration on Brook Trout Mortality in Acidified Streams of the Adirondack Mountains, New York, USA.

Mortality of brook trout Salvelinus fontinalis and water chemistry were characterized in 6 headwater streams in the western Adirondacks of New York during spring 2015, 2016, and 2017 and compared with results from analogous tests done between 1980 and 2003 in many of the same streams, to assess temporal changes in toxicity and inorganic monomeric aluminum (Al ) concentrations, and the role of Al exposure duration on brook trout survival. The Al concentrations of 2 and 4 µmol L corresponded to low-to-moderate and high mortality thresholds, but prolonged exposure to ≥1 µmol Al  L also produced mortality. The variability, mean, and highest Al concentrations in Buck Creek year round, and in several other streams during spring, have decreased significantly over the past 3 decades.

Ecological risk of methylmercury to piscivorous fish of the Great Lakes region.

Contamination of fish populations with methylmercury is common in the region of the Laurentian Great Lakes as a result of atmospheric deposition and methylation of inorganic mercury. Using fish mercury monitoring data from natural resource agencies and information on tissue concentrations injurious to fish, we conducted a screening-level risk assessment of mercury to sexually mature female walleye (Sander vitreus), northern pike (Esox lucius), smallmouth bass (Micropterus dolomieu), and largemouth bass (Micropterus salmoides) in the Great Lakes and in interior lakes, impoundments, and rivers of the Great Lakes region. The assessment included more than 43,000 measurements of mercury in fish from more than 2000 locations.

Trends in mercury concentrations in New York State fish.

Atmospheric emissions of mercury in the US are being reduced, but worldwide mercury emissions remain high. Mercury is also being removed from many consumer items. Changes over time in mercury concentrations in fish remain important to resource managers and the general public.