Effects of acid rain on the ecological health of Long Island’s forests and ponds

BACKGROUND 

Air emissions from the combustion of fossil fuels in electrical power plants, building heating systems and vehicles are the major source of gaseous sulfur (SOx) and nitrogen (NOx) oxides in the atmosphere. These oxides dissolve in atmospheric moisture forming ions which are deposited by rain, snowfall and dust particles as acidic deposition.  

Acidic deposition releases soluble aluminum from the soil which can reach toxic concentrations in adjacent water bodies such as streams and wetlands.  Acidic deposition also removes important nutrients such as calcium, potassium and magnesium from the soil negatively impacting local flora and fauna. Depletion of calcium combined with excess aluminum makes forest trees more susceptible to pests, pathogens and injury from freezing and drought. Additionally, in nutrient poor systems, deposition of nitrogen can have a fertilization effect, further altering aquatic and terrestrial systems. Preliminary data suggest that acid rain may also affect forests on finer textured and more mesic Long Island soils. 

The combustion of coal for electricity generation is the primary source of atmospheric emissions of mercury (Hg).  Additionally, on Long Island New York there are also local “waste-to-energy” municipal incinerators located in Hempstead and Babylon which emit mercury.  Mercury and its toxic organic form methylmercury (MeHg) present a significant stressor to wildlife populations.  Recent NYSERDA funded studies on Hg exposure in coastal wetlands and tidal marshes of Long Island have shown that saltmarsh sparrows accumulate harmful Hg levels in their blood in some but not all marshes. 

Coastal plain freshwater ponds embedded in the pitch pine-oak forests of the Long Island Central Pine Barrens are acidic and extremely nutrient poor, with water levels that fluctuate with changes in groundwater elevation. These ponds provide a unique natural environment with a large number of rare species.   Atmospheric deposition of acids, nutrients and Hg may be altering the chemical makeup of this environment, and these biogeochemical changes could have a detrimental effect on the rare plant and animal species of this landscape. 

Environments most impacted by the effects of acidic deposition are those that receive high deposition loads of SOx and NOx and which have poorly buffered soils, such as the Central Pine Barrens.  Mercury is transformed to MeHg most efficiently in acidic environments that receive high deposition loadings and experience frequent saturation and drying cycles.  All of these conditions exist in the Pine Barrens and conspire to make this unique region especially vulnerable to these pollutants. Mashomack Preserve with its mixed hardwood forests on finer textured and more mesic/fertile soils is typical of other Long Island forests and will serve as a comparison site to the Central Pine Barrens. The extensive historical, geological, chemical and biological data available for Mashomack Preserve may permit detailed interpretation of study results. 

PROJECT OVERVIEW 

This project is composed of two separate, but coordinated research surveys assessing mercury and acidification of the Long Island Pine Barrens.  These surveys will be undertaken by the US Geological Survey (hereafter the “Contractor) in Troy, NY and the BioDiversity Research Institute (BRI) in cooperation with the Long Island chapter of the Nature Conservancy (TNC).  

The acidification survey will conducted by the Contractor and shall include the collection and analysis of surface water, groundwater and soils.  The Hg exposure assessment will be undertaken by BRI.   All sample collections shall take place at the 6 sites listed in Table 1, with an additional 3 sites at the Mashomack Preserve on Shelter Island, Long Island, where soils and soil water will be collected. 

The Contractor, in coordination with the BRI, shall use the biotic and water chemistry data to help explain Hg concentrations in biota and determine if acid deposition has led to  coastal plain pond water chemistry that could result in methylation of mercury in these ponds. 

Table 1. Central Pine Barrens sites selected for the acidification study, Suffolk County, Long Island in 2012. 

 Project
Location by County

Suffolk County, NY