Ongoing efforts to improve the health of New York's South Shore Estuary Reserve (SSER) require continuously recorded water-quality data to understand the short-term effects of stormwater runoff and other pollution sources. To document the diel and tidal variability of water quality in the western bays of the SSER, the USGS
monitors select physical and chemical parameters at two sites within the SSER. One site, station 01310740 on Reynolds Channel at Point Lookout, is near the estuary mouth and operated in cooperation with the New York State Department of Environmental Conservation (NYSDEC)
and Town of Hempstead Department of Conservation & Waterways
. The second, station 01311143 on Hog Island Channel at Island Park, is at a mid-bay location and operated in cooperation with the New York Department of State through an agreement with the NYSDEC. This monitoring program (fig. 1) documents the diel and tidal variability of water quality across a gradient of eutrophication in the western bays; compliments the water-quality grab sampling efforts of the NYSDEC, other partners, and stakeholders; and provides information critical to the preparation and application of a nitrogen Total Daily Maximum Load (TMDL) for this system.
Both monitoring stations collect continuous data on tidal water elevations and select water-quality parameters that are being recorded at 6-minute intervals, and made publicly available via the Internet. Water-quality data on water temperature, specific conductance (used to compute salinity), dissolved oxygen, turbidity, and chlorophyll are collected from about 0.5 m above the seabed; at mid-bay station 01311143, data on pH and nitrate also are collected (fig. 2). Tidal statistics (for example, mean high and low water levels) and water-quality statistics (for example, maximum, minimum, and mean or median values) are published (online) annually in the USGS Water-Data Report for Long Island
Continuous monitoring reveals conditions and processes undetected by grab sampling, and documents the short-term variability of water-quality parameters. These data fluctuate in response to semi-diurnal and longer-period tides, reflecting differences in estuarine water quality due to oceanic, upland, and atmospheric influences. One example is an often-observed inverse relationship between nitrate and salinity over individual tidal cycles at mid-bay station 01311143 (fig. 3), suggesting that nitrate is predominantly supplied by freshwater inputs to the estuary (such as aquifer discharge), an implication supported by reports of elevated nitrogen concentrations in groundwater (typically as nitrate) discharging to the SSER (for example, Schubert and others, 2010, and Monti and Scorca, 2003). However, other instances where the comparatively high nitrate-low salinity relation is not apparent or is even reversed (not shown in fig. 3) may indicate the input (or loss) of nitrate is due to other factors. These findings underscore the need for more detailed information on freshwater inputs and nitrogen (nitrate) loads from wastewater treatment plant effluent and aquifer discharge to the estuary. Daily statistics illustrate seasonal and longer-term changes in water-quality parameters, and facilitate comparison of data between the two monitoring stations along a eutrophication gradient within the western bays. An example of this is shown in figure 4, which displays daily maximum, minimum, and mean values from calendar year 2011 for dissolved oxygen (DO) and chlorophyll. Figure 4 illustrates good to fair water quality and ecological conditions at station 01310740 near the estuary mouth, where daily mean DO always remained above the NYS Chronic Water Quality Standard (4.8 mg/L) and daily mean chlorophyll often remained below the U.S. Environmental Protection Agency (EPA)
Fair Ecological Condition Criterion (5 μg/L) during this period. In contrast, figure 4 generally shows fair to poor water quality and ecological condition at mid-bay station 01311143, where daily mean DO sometimes approached the NYS Chronic Water Quality Standard (4.8 mg/L), and daily mean chlorophyll often exceeded the EPA Poor Ecological Condition Criterion (>20 μg/L).
Schubert, C.E., deVries, M.P., and Finch, A.J., 2010, Nitrogen loads in groundwater entering back bays and ocean from Fire Island National Seashore, Long Island, New York: U.S. Geological Survey, Open-File Report 2010–1081, 16 p.
Monti, Jack, Jr., and Scorca, M.P., 2003, Trends in nitrogen concentration and nitrogen loads entering the South Shore Estuary Reserve from streams and ground-water discharge in Nassau and Suffolk Counties, Long Island, New York, 1952–97: U.S. Geological Survey Water-Resources Investigations Report 02–4255, 36 p .
Location by County
Suffolk County, NY, Nassau County, NY, New
York (Manhattan) County (FIPS 36061), NY, Kings County, NY, Queens County, NY, Richmond County, NY, Bronx County, NY, Westchester County, NY, Putnam County, NY, Orange County, NY, Dutchess County, NY, Albany County, NY, Columbia County, NY, Rensselaer County, NY