Grantee Research Project Results
2001 Progress Report: CISNet: Nutrient Inputs as a Stressor and Net Nutrient Flux as an Indicator of Stress Response in Delaware's Inland Bays Ecosystem
EPA Grant Number: R826945Title: CISNet: Nutrient Inputs as a Stressor and Net Nutrient Flux as an Indicator of Stress Response in Delaware's Inland Bays Ecosystem
Investigators: Ullman, William J. , Krantz, David E. , McKenna, Thomas E. , Madsen, John M. , Scudlark, Joseph R. , Andres, A. Scott , Wong, Kuo-Chuin
Institution: University of Delaware , University of Toledo
EPA Project Officer: Packard, Benjamin H
Project Period: October 1, 1998 through September 30, 2001 (Extended to September 30, 2002)
Project Period Covered by this Report: October 1, 2000 through September 30, 2001
Project Amount: $600,000
RFA: Ecological Effects of Environmental Stressors Using Coastal Intensive Sites (1998) RFA Text | Recipients Lists
Research Category: Environmental Statistics , Aquatic Ecosystems , Ecological Indicators/Assessment/Restoration
Objective:
This program is focused on the Delaware Inland Bays watershed, a member of the common, but understudied, class of shallow estuarine ecosystems. The objective of this program is to document the sources and sinks of nutrients (nitrogen, phosphorus, and organic carbon) to and from the Bays. This watershed receives excessive nutrient fluxes from agricultural, municipal, domestic, and industrial sources. These inputs lead to a number of undesirable consequences of eutrophication in the Bays. The specific goals of this study are to: (1) determine the sources, magnitudes, and spatial and temporal variability of nutrient fluxes to the Bays; (2) assess the magnitude of nutrient sinks in this system; and (3) develop conceptual and simple quantitative models that relate these nutrient inputs and outputs to more easily measured and monitored hydrological forcing parameters such as precipitation, temperature, wind speed and direction, season, groundwater levels, and surface-water discharge.Progress Summary:
Two independent correlation methods were used to estimate loadings from storms that were not sampled: one from the ratio of sampled flow volumes to total flow volumes, the other from the ratio of precipitation from sampled storms to total annual precipitation. Total dissolved nitrogen (TDN) unit loading rates for the heavily agricultural subwatersheds are similar to the rates estimated by previous researchers. Soil type appears to be less important than previous researchers have thought for estimating TDN loading. The TDN unit loading rate for an urbanized subwatershed, however, is much lower than the rates estimated in previous work. The TDN unit loading rate for a heavily forested subwatershed is slightly less than previous estimates. Total phosphorus (TP) loading rates are significantly lower than those previously estimated for any land use in the watershed. We believe that impoundments in this watershed trap particulate phosphorus (PP) and where it is subsequently converted to TDP. Total dissolved phosphorus (TDP) loads exceed PP loads from Millsboro Pond, the largest tributary to the Inland Bays. Also, it is possible, however, that the estimated TDP load is greater than the PP load from the other watersheds because PP is predominantly transported during storm events and all of the monitored storms were relatively small. High PP loads associated with larger storms may have been missed.Precipitation chemistry was monitored on an ongoing basis at Cape Henlopen State Park, under the auspices of the National Oceanic and Atmospheric Administration (NOAA) AIRMoN program to determine the direct input of atmospheric nitrogen to the Inland Bays ecosystem. A second monitoring site, closer to the Bays, has been established by this project to examine the impact of local nutrient sources (power plant emission and poultry houses). On the basis of these and earlier measurements, the atmospheric deposition of nitrogen provides between 14 and 24 percent of the total annual input to the Bays. During the summer, when wet and dry deposition are at their maxima and fluxes from all other sources are at their minima, the relative importance of atmospheric inputs of nitrogen to the Inland Bays is greater than implied by the annual averages. Neither of these determinations, however, account for direct gaseous ammonia deposition. To improve the seasonal and annual atmospheric nitrogen deposition estimates, the concentrations of gaseous ammonia, NH3(g), are being monitored at a number of sites in the watershed using passive samplers. These samplers also are being used to study the gaseous ammonia discharges from a single poultry production facility for the purpose of quantifying local sources in subwatersheds of the Inland Bays in which high concentrations of NH3(g) are found. Additional funding for this work was provided by the Center for Inland Bays, EPA National Estuary Program, and DNREC.
Both diffuse groundwater seepage and springs along the margins of the Bays were identified by an aerial thermal radiometer survey. A LANDSAT 7 image and additional thermal radiometer surveys were used, together with GIS software to identify other potential seeps or springs in the open-water parts of the bays and to demonstrate the relationship between the location of seepage zones and the underlying geology. The hydrostratigraphic framework is being refined by conducting geophysical surveys to provide information on the spatial connectivity of aquifers and aquitards as interpreted from boreholes. High-resolution seismic equipment imaged the subsurface to a depth of approximately10 meters with a vertical resolution on the order of decimeters. A resistivity survey conducted in collaboration with the U.S. Geological Survey was used to further map subsurface salinities on the meter scale. Coring of open water sites where resistivity anomalies were found has demonstrated the utility of this latter technology. Additional surveys with a towed thermistor array also have demonstrated the potential of this technology for the identification of seepage zones. Two groundwater discharge sites, one on Herring Creek and another in upper Indian River Bay, are currently instrumented to document the spatial and temporal variability of discharge and the importance of the subsurface geology in controlling the discharge. Measurements of groundwater seepage indicate significant discharge but large special variability. Temporally, seepage did not always correlate with tidal stage as expected by basic theory. Surveys of temperature and salinity along the coastline and in shallow tidal creeks were used to delineate areas of groundwater discharge at a smaller spatial scale than could be seen in remotely sensed images. A GIS database was compiled to facilitate spatial estimations of groundwater discharge and nutrient loading.
During the past year, a major survey in the Indian River Bay was conducted to measure the spatial distributions of current, temperature, and salinity in the bay. Six different moorings with 8 Inter Ocean S4 electromagnetic current meters were deployed from late March to early June at Indian River Inlet, Massey's Ditch, and the interior of the Indian River Bay. Concurrent with the current-meter survey and with additional support from the Delaware Sea Grant College Program, we also conducted an intensive CTD survey on a small research vessel to examine the large spatial variations in the salinity distribution around the Indian River Inlet. Using this data and concurrent wind and tidal records, we have processed the current meter data to separate the tidal and nontidal components of the flow at each site. These have been compared to data collected in previous years to look for seasonal and interannual variabilities. We have examined the relative importance of the local and remote wind effects in producing subtidal exchange within the bay to establish the basic exchange patterns associated with different wind conditions. These results will be used to infer subtidal exchange patterns for the whole CISNet sampling period. Recently, we have focused our attention on the factors that are important to the residual salt exchange in the bay. We have examined the contribution of the advection of salt by residual circulation and the residual salt transport induced by the tidal pumping effect. We will use the salt balance to infer nutrient balances during the periods in which current meters were deployed.
Surface water samples were collected monthly during the spring, summer, and fall for the determination of changing nutrient distributions within the Bays. These data currently are being used together with the determination of tributary, groundwater, oceanic, and atmospheric inputs of nitrogen, phosphorus, silicate, and organic carbon to determine the residence time of these nutrients in the Inland Bays ecosystem as a function of season and specific meteorological forcing parameters. These data also are being used, together with the distribution of planktonic algae (as determined by chlorophyll a) to develop indicators of changing patterns of N and P limitation of planktonic biomass, a factor that contributes to observed patterns of anoxia and fishkills in the Inland Bays.
Future Activities:
All sampling activities of this project have been completed and no further field work is contemplated. The analysis of samples for nutrient concentrations is the principal focus of the remaining laboratory efforts. The analysis of the CISNet data and the preparation of papers will continue through the end of the extended period of this grant.Journal Articles on this Report : 1 Displayed | Download in RIS Format
Other project views: | All 92 publications | 11 publications in selected types | All 6 journal articles |
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Type | Citation | ||
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Wong K-C. On the wind-induced exchange between Indian River Bay, Delaware and the adjacent continental shelf. Continental Shelf Research 2002, Volume: 22, Number: 11-13 (JUL-AUG), Page: 1651-1668. |
R826945 (2001) R826945 (Final) |
not available |
Supplemental Keywords:
watersheds, chemical transport, ecosystem, environmental chemistry, physics, hydrology, geology, Mid-Atlantic, Atlantic Coast., RFA, Scientific Discipline, Water, Geographic Area, Ecosystem Protection/Environmental Exposure & Risk, Water & Watershed, Hydrology, Ecology, Nutrients, Ecosystem/Assessment/Indicators, Ecosystem Protection, State, Chemistry, Ecological Effects - Environmental Exposure & Risk, Monitoring/Modeling, Air Deposition, Mid-Atlantic, Watersheds, bays, ecological exposure, aquatic ecosystem, environmental monitoring, fate and transport, coastal ecosystem, nutrient transport, stressors, meteorology, Delaware (DE), nutrient flux, coastal zone, public information, chemical speciation, CISNet Program, public reporting, Indian River Bay, soil, aquatic ecosystems, ecosystem, ecosystem health, water quality, nutrient cycling, stress responses, nutrients as stressors, Rehoboth Bay, nutrient transport model, atmospheric deposition, atmospheric chemistry, groundwaterRelevant Websites:
http://www.udel.edu/dgs/ftp/cisnet/CHEMDATA/
Progress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.