HR: 16:55h
AN: H14B-07    [Abstracts]
TI: Eutrophication Links between the Watershed and Estuary in the Neuse River Basin, NC
AU: * Showers, W J
EM: wjshower@unity.ncsu.edu
AF: Dept of Marine, Earth, & Atmospheric Sciences, North Carolina State University, Raleigh, NC 27695 United States
AU: Paerl, H W
EM: hpaerl@email.unc.edu
AF: Institute of Marine Sciences, University of North Carolina at Chapel Hill, Morehead City, NC 28557 United States
AB: The Neuse River drains into the Neuse River Estuary and Pamlico Sound, which is part of the second largest estuarine ecosystem in the United States and a key nursery for Mid and Southeast Atlantic fisheries. RiverNet, ModMon, and now FerryMon have monitored nutrient fluxes in the watershed and ecosystem responses in the estuary. Poor water quality in the 1980's led to a phosphorus ban in the basin that decreased P inputs to the watershed and improved water quality in the freshwater portions of the basin. High temporal resolution nutrient monitoring in the river indicates that significant flux variations are associated with point sources, and that N fluxes have been underestimated by previous monitoring efforts. N loss in the watershed is associated with hydric soils that are primarily located in the lower coastal plain. The ¹⁷O composition of nitrate suggests that Amospherically Deposited Nitrogen (A.D.N.) is event driven and is controlled by land use in the sub-basin. New regulations imposed by the State of NC are decreasing N fluxes in the watershed, but these fluxes are highly variable and controlled to some extent by extreme rainfall events that result from direct hurricane strikes and droughts. The greater decrease in P flux to the estuary compared to N flux (which has decreased slightly or remained the same) has reduced P-limited primary production in the freshwater upper portion of the estuary. This limits the N assimilation in this region, and allows more efficient N transport to N-sensitive coastal waters in the lower portion of the estuary. Chl a and phytoplankton pigment monitoring in the estuary indicate that site of the maximum primary productivity has moved form the upper estuary in the 1970's and 1980's to the lower estuary today. This displacement of the eutrophication gradient may explain the reduction of Cyanobacteria algae blooms in the upper estuary, and the increase in harmful algae blooms, hypoxia, and declines in fisheries habitats in the lower estuary. These findings underscore the need for basin scale nutrient reduction strategies that consider the entire freshwater-marine continuum, and the need for long term monitoring that take in account climatic and hydrological variability (i.e. hurricanes and droughts).
DE: 1030 Geochemical cycles (0330)
DE: 1040 Isotopic composition/chemistry
DE: 1845 Limnology
DE: 1871 Surface water quality
SC: Hydrology [H]
MN: 2005 Joint Assembly