William G. Reay

Sources of nitrogen to estuaries in the United States

The purpose of this study was to quantify the nitrogen (N) inputs to 34 estuaries on the Atlantic and Gulf Coasts of the United States. Total nitrogen (TN) inputs ranged from 1 kg N ha−1 yr−1 for Upper Laguna Madre, Texas, to 49 kg N ha−1 yr−1 for Massachusetts Bay, Massachusetts. TN inputs to 11 of the 34 estuaries were dominated by urban N sources (point sources and septic systems) and nonpoint source N runoff (5% of total); point sources accounted for 36–86% of the TN inputs to these 11 urban-dominated estuaries. TN inputs to 20 of the 34 estuaries were dominated by agricultural N sources; N fertilization was the dominant source (46% of the total), followed by manure (32% of the total) and N fixation by crops (16% of the total). Atmospheric deposition (runoff from watershed plus direct deposition to the surface of the estuary) was the dominant N source for three estuaries (Barnegat Bay, New Jersey: 64%; St. Catherines-Sapelo, Georgia: 72%; and Barataria Bay, Louisiana: 53%). Six estuaries had atmospheric contributions ≥30% of the TN inputs (Casco Bay, Maine: 43%; Buzzards Bay, Massachusetts: 30%; Great Bay, New Jersey: 40%; Chesapeake Bay: 30%; Terrebonne-Timbalier Bay, Louisiana: 59%; and Upper Laguna Madre: 41%). Results from our study suggest that reductions in N loadings to estuaries should be accomplished by implementing watershed specific programs that target the dominant N sources.

Base flow nutrient discharges from lower Delmarva Peninsula watersheds of Virginia, USA.

Proper management of shallow coastal systems, which are vulnerable to nutrient enrichment, requires knowledge of land use impacts on nutrient discharges. This study quantified base flow nutrient concentrations and yields for 1 yr (May 2001-April 2002) from 14 first-order streams on the Virginia Eastern Shore (VaES) on the Delmarva Peninsula and assessed their relationships with land cover and soil drainage class in their watersheds. Base flow water discharge rates (1.4-31.5 cm yr(-1)) were likely lower than the long-term average due to a severe drought. Seasonal mean nitrate concentrations were higher in winter, while mean dissolved organic carbon and ammonium concentrations were higher in summer. Annual base flow-weighted mean total dissolved nitrogen (TDN) concentrations were positively related to percent (%) agricultural land cover (r(2) = 0.43; p = 0.02) and % very poorly drained soils (r(2) = 0.51; p = 0.009) and negatively related to % forested land cover (r(2) = 0.54; p = 0.005). Patterns of base flow TDN yields were similar to those of concentrations but were also positively related to % developed land cover (r(2) = 0.40; p = 0.03). Agricultural and developed land covers, together with very poorly drained soil, accounted for 91% of the variability of TDN yields (p = 0.0001). Using a multiple regression model, the base flow TDN loading rate to a coastal lagoon on the VaES, a system vulnerable to nutrient enrichment, was estimated to be 28,170 kg N yr(-1).

Sea level driven marsh expansion in a coupled model of marsh erosion and migration

Coastal wetlands are among the most valuable ecosystems on Earth, where ecosystem services such as flood protection depend nonlinearly on wetland size and are threatened by sea level rise and coastal development. Here we propose a simple model of marsh migration into adjacent uplands and couple it with existing models of seaward edge erosion and vertical soil accretion to explore how ecosystem connectivity influences marsh size and response to sea level rise. We find that marsh loss is nearly inevitable where topographic and anthropogenic barriers limit migration. Where unconstrained by barriers, however, rates of marsh migration are much more sensitive to accelerated sea level rise than rates of edge erosion. This behavior suggests a counterintuitive, natural tendency for marsh expansion with sea level rise and emphasizes the disparity between coastal response to climate change with and without human intervention.

Water Quality within the York River Estuary

Abstract Key water quality management issues and threats within the Chesapeake Bay and its tidal tributaries include excess loadings of sediment and nutrients, and the introduction of toxic chemicals and microbial agents. Poor water clarity, principally controlled by suspended sediments and phytoplankton, is a persistent and widespread problem in the York River estuary with the oligohaline and middle mesohaline regions failing to meet submerged aquatic vegetation (SAV) habitat requirements (SAV criteria: ~10 NTU and TSS < 15 mg L−1). Both the primary and more localized secondary estuarine turbidity maximum are associated with these regions where elevated surface (30–35 mg L−1) and bottom (80–105 mg L−1) water TSS levels are observed. While nonpoint agriculture sources dominate riverine sediment load inputs, tidal and nearshore erosion are a significant source of suspended sediment in the York River estuary. As with sediment, nonpoint agricultural sources dominate nutrient inputs and streamflow is a dominant controlling factor in explaining variability in annual loads. Within mainstem surface waters, TDN and TDP concentrations exhibit a decreasing trend with increasing salinity. TDN and TDP concentrations are on the order of 40–45 μmol L−1 and 1.2 μmol L−1, respectively, in the tidal freshwater reaches of the Pamunkey and Mattaponi Rivers and 22–24 μmol L−1 and 0.6 μmol L−1 in the polyhaline regions of the York River. Mean DON exhibits little variation between salinity regimes. Seasonal phytoplankton biomass and productivity vary between salinity regimes with mean monthly peak chlorophyll a concentrations on the order of 9–10 μg L−1 in the tidal freshwater reaches, 14–18 μg L−1 in the transition zone below the freshwater region, 25–28 μg L−1 in the upper and middle mesohaline reaches, and 15 μg L−1 in the lower mesopolyhaline region. Based on DIN:DIP molar ratios and limited nutrient enrichment studies, tidal freshwater regions experience year-round phosphorus limitation, shifting to seasonal nitrogen limitation in the lower oligo, meso and polyhaline regions of the York River. Harmful algal bloom (HAB) producing dinoflagelletes have resulted in “red tides” that generally occur annually (summer, early fall) in the lower York River. With respect to low dissolved oxygen levels, hypoxia derived from oxidation of organic matter and sediment oxygen demand has also been observed repeatedly in the bottom waters of the lower, high salinity reaches when water temperatures exceed 20 °C. While studies have indicated limited toxic chemical contamination, mercury and PCB fish consumption advisories and restrictions have been issued within the York River estuary. Mercury impacted regions of the Mattaponi and Pamunkey Rivers receive significant wetland drainage that can enhance the potential for bioaccumulation of mercury in fish. Sediments in the York River proper exhibit PCB levels ranging from 1–5 ppb with more elevated levels (25 ppb) being observed in some contributing tidal creeks. In contrast to mercury where atmospheric deposition is a primary pathway, PCBs are generally released into the environment from runoff processes occurring at hazardous waste sites. With varying sources of fecal pollution, 20 percent (31.1 km2) of the York Rivers assessed shellfish waters has been designated as impaired. Condemned waters are restricted to major industrial and defense facility sites, and contributing smaller tidal creek systems.

System-Wide Monitoring Program of the National Estuarine Research Reserve System: Research and Monitoring to Address Coastal Management Issues

Abstract The National Estuarine Research Reserve System (NERRS) consists of 28 coastal reserves located across the United States. A system-wide monitoring program was established in 1995 to develop quantitative measurements of short-term variability and long-term changes in abiotic and biotic properties of estuarine ecosystems for the purpose of informing effective coastal management. The hallmarks of this program are its two decades of data collection, the use of common protocols and instrumentation across all observing platforms, and a centralized approach to data quality assurance/quality control (QA/QC). By using standardized procedures at all reserves, this monitoring program generates a national database on estuarine ecosystems, and it creates a network of sentinel sites for detecting and understanding the effects of climate change. Examples of how these data inform coastal managers include water quality assessment, habitat mapping and change analysis, establishment of nutrient criteria for estuaries, and understanding the predicted impacts of climate change.

Introduction to the Chesapeake Bay National Estuarine Research Reserve in Virginia

Abstract Designated in 1991, CBNERRVA established a multi-component system along the salinity gradient of the York River estuary that encompassed the diverse collection of habitats found within the southern Chesapeake Bay subregion. With its two principal tributaries, the Pamunkey and Mattaponi Rivers, the York River is the Bays fifth largest tributary in terms of flow and watershed area. The York River estuary is classified as a microtidal, partially mixed estuary. Tidal range varies from 0.7 m and at its mouth to over 1 m in the upper freshwater tributary reaches and salinity distribution ranges from tidal freshwater to polyhaline regimes. Land use is predominantly rural in nature with forest (61%) and agricultural lands (21%) being the dominant land cover; wetlands comprise approximately 7% of the basins area. Reserve components include: (1) Goodwin Islands (148 ha), an archipelago of polyhaline salt-marsh islands surrounded by inter-tidal flats, extensive submerged aquatic vegetation beds, and shallow open estuarine waters near mouth of the York River; (2) Catlett Islands (220 ha), consisting of multiple parallel ridges of forested wetland hammocks, maritime-forest uplands, and emergent mesohaline salt marshes; (3) Taskinas Creek (433 ha), containing non-tidal feeder streams that drain oak-hickory forests, maple-gum-ash swamps and freshwater marshes which transition into tidal oligo and mesohaline salt marshes; and (4) Sweet Hall Marsh (443 ha), an extensive tidal freshwater-oligohaline marsh ecosystem located in the Pamunkey River, one of two major tributaries of the York River. CBNERRVA manages these reserves to support informed management of coastal resources by supporting research that advances the scientific understanding of watershed and estuarine systems, highlighting proper stewardship of coastal resources, and improving general public and professional literacy through education and training programs.

Author Correction: Accuracy and Precision of Tidal Wetland Soil Carbon Mapping in the Conterminous United States

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