Grantee Research Project Results
2000 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 , United States Geological Survey
Current 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, 1999 through September 30, 2000
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: determine the sources, magnitudes, and spatial and temporal variability of nutrient fluxes to the Bays; assess the magnitude of nutrient sinks in this system; and 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:
Baseflow discharges of nutrients from tributary streams to the Bays have been sampled throughout the year since the beginning of the project. At six of these sites, stormwater discharges also were sampled from November 1998 to March 2000 in collaboration with the Delaware Department of Natural Resources and Environmental Control (DNREC). In some tributaries, the concentrations of dissolved nutrients appear to vary little and therefore the net flux from these tributaries appears to be primarily dependent on the rate of water discharge. In other streams, the concentrations of nutrients appear to vary with discharge. It is, therefore, not appropriate to use discharge alone as an indicator of the seasonal variability of nutrient fluxes from the watershed to the Bay as has been done in the past. Land use/land cover appears to impact the character of nutrient fluxes from tributaries and the dependence of nutrient concentrations on discharge. Additional work on the impact of land use/land cover on discharge has been initiated with additional funding from the Delaware Water Resource Research Center.
Precipitation chemistry was monitored on an ongoing basis at Cape Henlopen State Park, under the auspices of the 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 (powerplant 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.
The groundwater component of the CISNet project consists of three tasks: (1) to determine locations of submarine discharge areas, (2) to refine the hydrostratigraphic framework, and (3) to instrument, measure, and map groundwater discharge and nutrient flux at three sites to better conceptualize the discharge process. Both diffuse seepage and springs along the margins of the bays were identified by an aerial thermal radiometer survey. A recently acquired LANDSAT 7 image was used to identify other potential seeps or springs in the open-water parts of the bays. 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. An ~80-kilometer-long high-resolution seismic survey imaged the subsurface to a depth of ~10 meters with a vertical resolution on the order of decimeters. A resistivity survey conducted in collaboration with the U.S. Geological Survey (USGS) was used to further map subsurface salinities on the meter scale. Three discharge sites were identified for detailed study. One such site on Herring Creek is currently instrumented to document the spatial and temporal variability of discharge and the importance of the subsurface geology in controlling the discharge. Measured groundwater seepage at the site ranges from 0.5-7x10-8 m3/m2/s at different measurement locations and varies by >1x10-8 m3/m2/s with tidal stage at a given site. Strong upward vertical hydraulic gradients of 0.01-0.02 at well clusters in this highly permeable water-table aquifer indicate a strong potential for groundwater discharge. Heads in the wells are strongly correlated to the tidal stage of the adjacent creek. Surveys of temperature and salinity along the coastline and in the shallow adjacent creek delineate areas of groundwater discharge at a smaller spatial scale than could be seen in the remotely sensed images.
One field survey was conducted at Indian River Inlet to examine the characteristics of the exchange between the inland bays and the adjacent continental shelf. Three Inter Ocean S4 current meters were deployed from a single taut wire mooring to measure the near-surface, mid-depth, and near-bottom current there from March 26 to June 3, 2000; sea level elevations were obtained from the NOS tide gauge at Lewes, Delaware, and wind measurements from a NDBC buoy located 30 km offshore. This data set was examined in conjunction with data sets collected in previous years to determine the nature of wind-induced exchange through the inlet. Wind can generate vigorous low frequency currents in the inlet in excess of 25-30 cm/s at time scales of 2-5 days. About 85 percent of the variance in the subtidal current fluctuations in the inlet can be characterized by two component modes. The first mode, accounting for about 67 percent of the variance, corresponds to an unidirectional inflow or outflow throughout the water column, with only a minor decrease in current magnitude with depth. The second mode, with about 18 percent of the variance, corresponds to a bi-directional flow field with currents in the upper and lower layers flowing in opposite directions. The first mode represents the response of the Inland Bays to the remote atmospheric effect, with water being pumped into the bay under downwelling favorable wind conditions on the continental shelf, and vice versa. The second mode represents the response of the bay to the local wind effect, with the surface current flowing in the downwind direction along the longitudinal axis of the Indian River Bay and the bottom current flowing with the locally induced setup in the bay in the upwind direction.
Surface water samples continue to be 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, 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.
Future Activities:
At present, the baseflow and storm discharge results are being entered into a database management system (using Microsoft Access) to allow access by all of the CISNet investigators and collaborators from State and Federal agencies. The database will continue to be upgraded to allow for easier data entry, quality control and assurance, manipulation, graphical viewing, and data analysis by CISNet users. Work continues on the determination of nutrient concentrations and fluxes in all reactive forms to the Bays and the importance of local versus regional sources of nitrogen species to the Inland Bays. Baseflow and surface water sampling and analysis will continue through this next year. An additional deployment of current meters at Indian River Inlet is planned to further study the impact of tidal and sub-tidal exchange on nutrient fluxes and the role of winds velocity on exchange rates. This new survey will include additional current measurements in the interior of the Indian River Bay. The effort to synthesize all of the current and tidal data collected continues. In addition, we are currently instrumenting the second of two groundwater observatories for the determination of the role of underlying geology on the focusing of discharge and for the determination of nutrient fluxes from these focused sites. Analysis of water, salt, and nutrient exchange continues and the analysis of the distributions of nutrients in the surface waters of the Bays is beginning. Sediment sampling and continuing geophysical surveying will be completed in the next year.
Journal Articles:
No journal articles submitted with this report: View all 92 publications for this projectSupplemental Keywords:
watersheds, chemical transport, ecosystem, environmental chemistry, physics, hydrology, geology, Mid-Atlantic, Atlantic Coast., RFA, Scientific Discipline, Geographic Area, Water, Ecosystem Protection/Environmental Exposure & Risk, Hydrology, Nutrients, Ecology, Water & Watershed, Ecosystem/Assessment/Indicators, Ecosystem Protection, Chemistry, State, Monitoring/Modeling, Ecological Effects - Environmental Exposure & Risk, 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.