Assessing the Effects of Nutrient Management in an Estuary Experiencing Climatic Change: The Neuse River Estuary, North Carolina |
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Authors: | Hans W Paerl Lexia M Valdes Michael F Piehler Craig A Stow |
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Institution: | (1) Institute of Marine Sciences, University of North Carolina at Chapel Hill, 3431 Arendell Street, Morehead City, North Carolina 28557, USA;(2) Department of Environmental Health Sciences, Norman J. Arnold School of Public Health University of South Carolina, Health Sciences Building 800 Sumter Street , Columbia, South Carolina 29208, USA |
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Abstract: | Eutrophication is a serious water quality problem in estuaries receiving increasing anthropogenic nutrient loads. Managers
undertaking nutrient-reduction strategies aimed at controlling estuarine eutrophication are faced with the challenge that
upstream freshwater segments often are phosphorus (P)-limited, whereas more saline downstream segments are nitrogen (N)-limited.
Management also must consider climatic (hydrologic) variability, which affects nutrient delivery and processing. The interactive
effects of selective nutrient input reductions and climatic perturbations were examined in the Neuse River Estuary (NRE),
North Carolina, a shallow estuary with more than a 30-year history of accelerated nutrient loading and water quality decline.
The NRE also has experienced a recent increase in Atlantic hurricanes and record flooding, which has affected hydrology and
nutrient loadings. The authors examined the water quality consequences of selective nutrient (P but not N) reductions in the
1980s, followed by N reductions in the 1990s and an increase in hurricane frequency since the mid-1990s. Selective P reductions
decreased upstream phytoplankton blooms, but increased downstream phytoplankton biomass. Storms modified these trends. In
particular, upstream annual N and P concentrations have decreased during the elevated hurricane period. Increased flushing
and scouring from storms and flooding appear to have enhanced nutrient retention capabilities of the NRE watershed. From a
management perspective, one cannot rely on largely unpredictable changes in storm frequency and intensity to negate anthropogenic
nutrient enrichment and eutrophication. To control eutrophication along the hydrologically variable freshwater–marine continuum,
N and P reductions should be applied adaptively to reflect point-source–dominated drought and non–point-source–dominated flood
conditions. |
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Keywords: | Climate change Estuaries Eutrophication Hurricanes Nitrogen Nutrient management Phosphorus Water quality |
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