Resuspension and estuarine nutrient cycling: insights from the Neuse River Estuary

Abstract. For at least the past several decades, North Carolina's Neuse River Estuary (NRE) has been subject to water quality problems relating to increased eutrophication. Research studies initiated in the past several years have addressed the complex nutrient cycles in this system. Most of this research, however, is concerned with the nutrient processes of the water column and the passive diffusion processes of the benthic sedimentary environment. Resuspension of bottom sediments, by bioturbation, tides, or wind-generated waves, may have a significant effect on the flux of nutrients in an estuarine system These processes can result in the advective transport of sediment porewater, rich with nitrogen, phosphorus and carbon, into the water column. Thus, estimates of nutrient and carbon inputs from the sediments may be too low. This study focused on the potential change in porewater and bottom water nutrient concentrations associated with measured resuspension events. Previous research used short-lived radionuclides and meteorological data to characterize the sediment dynamics of the benthic system of the estuary. These techniques in conjunction with the presented porewater inventories allowed evaluation of the depth to which sediments have been disturbed and the advective flux of nutrients to the water column. The largest removal episode occurred in the lower NRE as the result of a wind event and was estimated that the top 2.2 cm of sediment and corresponding porewater were removed. NH4+ advective flux (resuspended) was 2 to 6 times greater than simply diffusion. Phosphate fluxes were estimated to be 15 times greater than the benthic diffusive flux. Bottom water conditions with elevated NH4+ and PO43− indicate that nutrients stored in the sediments continue to play an important role in overall water quality and this study suggests that the advective flux of nutrients to the water column is critical to understand estuarine nutrient cycling.

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Resuspension and estuarine nutrient cycling: insights from the Neuse River Estuary

Biogeosciences ◽

10.5194/bg-7-3289-2010 ◽

2010 ◽

Vol 7 (10) ◽

pp. 3289-3300 ◽

Cited By ~ 29

Author(s):

D. R. Corbett

Keyword(s):

Water Quality ◽

Nutrient Cycling ◽

Water Column ◽

Bottom Water ◽

River Estuary ◽

Neuse River Estuary ◽

Nutrient Concentrations ◽

Neuse River ◽

Advective Flux ◽

The Past

Abstract. For at least the past several decades, North Carolina's Neuse River Estuary (NRE) has been subject to water quality problems relating to increased eutrophication. Research initiated in the past several years have addressed the nutrient processes of the water column and the passive diffusion processes of the benthic sedimentary environment. Resuspension of bottom sediments, by bioturbation, tides, or winds, may also have a significant effect on the flux of nutrients in an estuarine system These processes can result in the advective transport of sediment porewater, rich with nitrogen, phosphorus and carbon, into the water column. Thus, estimates of nutrient and carbon inputs from the sediments may be too low. This study focused on the potential change in bottom water nutrient concentrations associated with measured resuspension events. Previous research used short-lived radionuclides and meteorological data to characterize the sediment dynamics of the benthic system of the estuary. These techniques in conjunction with the presented porewater inventories allowed evaluation of the depth to which sediments have been disturbed and the advective flux of nutrients to the water column. The largest removal episode occurred in the lower NRE as the result of a wind event and was estimated that the top 2.2 cm of sediment and corresponding porewater were removed. NH4+ advective flux (resuspended) was 2 to 6 times greater than simply diffusion. Phosphate fluxes were estimated to be 15 times greater than the benthic diffusive flux. Bottom water conditions with elevated NH4+ and PO43− indicate that nutrients stored in the sediments continue to play an important role in overall water quality and this study suggests that the advective flux of nutrients to the water column is critical to understand estuarine nutrient cycling.

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Mitigating Impacts of Natural Hazards on Fishery Ecosystems

Mitigating Impacts of Natural Hazards on Fishery Ecosystems ◽

10.47886/9781934874011.ch9 ◽

2008 ◽

Keyword(s):

Water Quality ◽

Nutrient Loading ◽

Water Quality Management ◽

River Estuary ◽

Chemical Properties ◽

Neuse River Estuary ◽

Estuarine System ◽

Nutrient Loads ◽

Habitat Alterations ◽

The Past

<em>Abstract</em>.—Since the mid-1990s, the U.S. mid-Atlantic region has witnessed a sudden rise in hurricane and tropical storm landfalls. In particular, eastern North Carolina has been impacted by eight hurricanes and six tropical storms in the past decade, and this relatively high frequency is forecast to continue for the next several decades. Each of the past storms exhibited unique hydrologic and nutrient loading scenarios for the Pamlico Sound, the United States’ second largest estuarine system and its largest subestuary, the Neuse River estuary. This variability represents a challenge to nutrient management aimed at protecting water quality and ensuring optimal fisheries habitat conditions. Different rainfall amounts among hurricanes led to variable freshwater and nutrient discharge and hence variable nutrient, organic matter, and sediment enrichment. These enrichments differentially affected physical and chemical properties (salinity, water residence time, transparency, stratification, dissolved oxygen), phytoplankton primary production, and phytoplankton community composition. The contrasting effects were accompanied by biogeochemical perturbations (hypoxia, enhanced nutrient cycling), benthic and planktonic habitat alterations, and possibly food web disturbances. Floodwaters from the two largest hurricanes, Fran (1996) and Floyd (1999), exerted multimonth to multiannual effects on hydrology, nutrient loads, productivity, biotic composition, and habitat condition. In contrast, relatively low rainfall coastal hurricanes like Isabel (2003) and Ophelia (2005) caused strong vertical mixing and storm surges but exhibited relatively minor hydrologic, nutrient, and biotic impacts. Both hydrologic and wind forcing are important drivers and must be integrated with nutrient loading in assessing short- and long-term ecological impacts of these storms. These climatic forcings cannot be managed but must be considered when developing water quality management strategies for these and other large estuarine ecosystems faced with increasing frequencies and intensities of hurricane activity.

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