Ecosystem impacts of three sequential hurricanes (Dennis, Floyd, and Irene) on the United States' largest lagoonal estuary, Pamlico Sound, NC

Three sequential hurricanes, Dennis, Floyd, and Irene, affected coastal North Carolina in September and October 1999. These hurricanes inundated the region with up to 1 m of rainfall, causing 50- to 500-year flooding in the watershed of the Pamlico Sound, the largest lagoonal estuary in the United States and a key West Atlantic fisheries nursery. We investigated the ecosystem-level impacts on and responses of the Sound to the floodwater discharge. Floodwaters displaced three-fourths of the volume of the Sound, depressed salinity by a similar amount, and delivered at least half of the typical annual nitrogen load to this nitrogen-sensitive ecosystem. Organic carbon concentrations in floodwaters entering Pamlico Sound via a major tributary (the Neuse River Estuary) were at least 2-fold higher than concentrations under prefloodwater conditions. A cascading set of physical, chemical, and ecological impacts followed, including strong vertical stratification, bottom water hypoxia, a sustained increase in algal biomass, displacement of many marine organisms, and a rise in fish disease. Because of the Sound's long residence time (≈1 year), we hypothesize that the effects of the short-term nutrient enrichment could prove to be multiannual. A predicted increase in the frequency of hurricane activity over the next few decades may cause longer-term biogeochemical and trophic changes in this and other estuarine and coastal habitats.

[1]  L. Crowder,et al.  NEUSE RIVER ESTUARY MODELING AND MONITORING PROJECT STAGE 1: EFFECTS OF WATER QUALITY ON DISTRIBUTION AND COMPOSITION OF THE FISH COMMUNITY , 2000 .

[2]  H. Paerl,et al.  RESPONSES OF THE PHYTOPLANKTON COMMUNITY GROWTH RATE TO NUTRIENT PULSES IN VARIABLE ESTUARINE ENVIRONMENTS , 1999 .

[3]  John A. Knaff,et al.  Atlantic Basin Hurricanes: Indices of Climatic Changes , 1999 .

[4]  Hans W. Paerl,et al.  Ecosystem Responses to Internal and Watershed Organic Matter Loading: Consequences for Hypoxia in the Eutrophying Neuse River Estuary, North Carolina, USA , 1998 .

[5]  H. Lenihan,et al.  HOW HABITAT DEGRADATION THROUGH FISHERY DISTURBANCE ENHANCES IMPACTS OF HYPOXIA ON OYSTER REEFS , 1998 .

[6]  R. Christian,et al.  Dynamics of NH4+ and NO3− uptake in the water column of the Neuse River Estuary, North Carolina , 1994 .

[7]  S. Baden,et al.  Effects of periodic hypoxia on distribution of demersal fish and crustaceans , 1991 .

[8]  H. Paerl,et al.  Stimulation of phytoplankton production in coastal waters by natural rainfall inputs: Nutritional and trophic implications , 1990 .

[9]  W. Lampert.  Laboratory studies on zooplankton‐cyanobacteria interactions , 1987 .

[10]  D. Stanley.  Nitrogen Cycling and Phytoplankton Growth in the Neuse River, North Carolina , 1983 .

[11]  L. Eugene Cronin,et al.  Estuaries and Nutrients , 1981, Contemporary Issues in Science and Society.

[12]  V. Kennedy.  The Effects of Tropical Storm Agnes on the Chesapeake Bay Estuarine System , 1979 .

[13]  A. Sallenger,et al.  Two months of floodings in eastern North Carolina, September-October 1999 : hydrologic, water quality, and geologic effects of Hurricanes Dennis, Floyd, and Irene , 2000 .

[14]  J. Bales,et al.  Simulation of hydrodynamics and solute transport in the Neuse River estuary , 1995 .

[15]  J. Bales,et al.  Simulation of hydrodynamics and solute transport in the Pamlico River estuary, North Carolina , 1995 .

[16]  Hans W. Paerl,et al.  Nitrogen Loading Sources and Eutrophication of the Neuse River Estuary, North Carolina: Direct and Indirect Roles of Atmospheric Deposition , 1995 .

[17]  R. Benner,et al.  A critical evaluation of the analytical blank associated with DOC measurements by high-temperature catalytic oxidation , 1993 .

[18]  D. Knott,et al.  An evaluation of the survival of experimental populations exposed to hypoxia in the Savannah River estuary , 1992 .

[19]  R. Christian,et al.  Significance of euphotic sediments to oxygen and nutrient cycling in a temperate estuary , 1992 .

[20]  R. Christian,et al.  Multi-year distribution patterns of nutrients within the Neuse River Estuary, North Carolina , 1991 .

[21]  T. M. Nelson,et al.  Bibliography of hydrologic and water-quality investigations conducted in or near the Albermarle-Pamlico Sounds Region, North Carolina , 1988 .

[22]  H. Paerl.  FACTORS REGULATING NUISANCE BLUE-GREEN ALGAL BLOOM POTENTIALS IN THE LOWER NEUSE RIVER, NC. , 1983 .

[23]  M. Brinson,et al.  Biogeochemistry of the sediments of the Pamlico and Neuse River estuaries, North Carolina , 1983 .

[24]  H. Paerl.  Factors regulating nuisance blue-green algal bloom potentials in the lower Neuse River, North Carolina , 1983 .

[25]  E. Kuenzler,et al.  Phytoplankton uptake and sediment release of nitrogen and phosphorus in the Chowan River, North Carolina , 1982 .

[26]  G. G. Parker,et al.  Hydrology of major estuaries and sounds of North Carolina , 1979 .

[27]  Jackson Davis,et al.  The effects of tropical storm Agnes on the Chesapeake Bay estuarine system , 1976 .

[28]  G. F. Humphrey,et al.  New spectrophotometric equations for determining chlorophylls a, b, c1 and c2 in higher plants, algae and natural phytoplankton , 1975 .

[29]  Austin B. Williams,et al.  A hydrographic atlas of larger North Carolina sounds , 1973 .