Water Quality Status of Georgia Estuaries and Coastal Waters Using Recommended Indicators
Sheldon, Joan E.
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Water quality is a concern in many estuaries, and the U.S. EPA has mandated the development of numeric nutrient criteria to assess the status of U.S. coastal waters. We have proposed a suite of seven indicators that are intended to help classify and understand the causes of water quality degradation in Georgia by covering the progression of eutrophication from nutrient over-enrichment to algal overgrowth (if present) to enhanced microbial respiration and hypoxia. Of these, we are able to assess four indicators coastwide using data collected by GA DNR CRD during 2003-2006. pH status was assessed using ΔpH, the deviation from the expected pH according to the sample salinity and estuary type (alluvial/tidewater, blackwater, alkaline blackwater). Annual median pH deviations were classified as good at almost all sites in all years, whereas annual minimum pH deviations often ranged into the fair and poor categories. pH status generally improved from 2004 to 2006. Annual median dissolved oxygen (DO) was mainly good to fair, while annual minimum DO was mainly fair to poor, with sites classified as poor occurring sporadically along the coast. DO status generally improved from 2003 to 2006. Annual median dissolved inorganic nitrogen status was mostly fair coastwide in all years, with the few sites classified as poor concentrated in the Altamaha River estuary. Annual median total dissolved phosphorus was fair coastwide during the study period. The generally poorer water quality in 2003 compared to later years may have been due to conditions related to high rainfall after a severe drought.