Webinar on December 18: A Clean Air Act Success Story

A Clean Air Act Success Story: Evidence of Chemical and Biological Recovery in an Acidified Catskill Mountain River, New York

Wednesday, December 18, 2019
1:00 pm Eastern Time

Barry Baldigo
Research Biologist
U.S. Geological Survey
New York Water Science Center

Registration Link:

AFS thanks the Water Quality Section for sponsoring this webinar!

Decades of acidic deposition have adversely affected aquatic and terrestrial ecosystems in acid-sensitive watersheds in parts of the eastern US. The national Acid Rain Program (Title IV of the 1990 amendments to the Clean Air Act – CAA) helped reduce emissions of sulfur dioxide (SO2) and nitrogen oxides (NOx) and resulted in sharp decreases in the acidity of atmospheric deposition. The decrease in acidic deposition produced a steady decline in the acidity of streams in many poorly-buffered waters across the western Adirondacks and parts of the Catskill Mountains of New York. Until recently, however, there has been little evidence of biological recovery in most acid sensitive streams in both regions. Long-term deposition and stream-chemistry records and fish-community data from quantitative surveys done during 1991-93 and again during 2017-19 at 16 sites in the upper Neversink River Basin were evaluated to determine if chemical and biological recovery were evident in this Catskill Mountain watershed and if they could be linked to regional declines in acidic deposition. Between 1991 and 2019, large decreases in sulfate and nitrate deposition in the basin mirrored declines in total nationwide SO2 and NOx emissions. There were corresponding decreases in sulfate and nitrate concentrations in deposition at the National Atmospheric Deposition station at Biscuit Brook (NY68) and coincident declines in sulfate concentrations at four stream monitoring sites in the upper Neversink. Inorganic aluminum concentrations decreased to, or below, an acute toxicity threshold of 2.0 µmol/L at several severely acidified sites and below a chronic toxicity threshold of 1.0 µmol/L at other moderately acidified sites. During the 26-year interval between fish surveys, total species richness along with the density and biomass of Brook Trout populations (and entire fish communities) increased at most sites experiencing chemical recovery. Although recovery is far from complete, trends in deposition chemistry, water quality, and fish assemblages in the upper Neversink Basin indicate that the 1990 amendments to the CAA is beginning to have its intended (positive) effect on stream ecosystems in this region.


Presenter biosketch:
Barry Baldigo has been a Research Biologist at the USGS, New York Water Science Center since 1990. He received his Master’s degree from SUNY ESF in 1982 and worked for the University of Nevada, Lockheed, and the Adirondack Lakes Survey Corporation between 1980 and 1990. Barry currently leads (or co-leads) several collaborative research efforts that are striving to improve our understanding of the health of aquatic ecosystems, the effects of environmental stressors on these systems, and the management options which might help mitigate adverse impacts of various stressors in waters across New York. He has published more than 60 journal articles and government reports and serves as an AE for the journal Transactions of the American Fisheries Society.