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Current CHRP Research Projects

Observations and Modeling of Narragansett Bay Hypoxia and Its Response to Nutrient Management


Daniel Codiga (Lead PI), Candace Oviatt, Heather Stoffel, Daniel Ullman University of Rhode Island, Graduate School of Oceanography
Susan Kiernan Rhode Island Department of Environmental Management, Office of Water Resources
Christopher Deacutis Narragansett Bay Estuary Program/Rhode Island Department of Environmental Management, Fisheries and Wildlife
Warren Prell Brown University
Jamie Vaudrey, James Kremer University of Connecticut at Avery Point
Mark Brush College of William and Mary, Virginia Institute of Marine Sciences

Narragansett Bay (NB) is a mid-size temperate estuary representative of many systems impacted by seasonal-periodic hypoxia. It is unusual relative to most other systems in that its nitrogen load is concentrated in wastewater treatment facility outputs, and that a very substantial load reduction (target 50%) is currently underway. This context makes NB an ideal setting for development and application of observational and modeling tools and analyses that (a) help agencies assess the response of hypoxia to nutrient management and (a) inform the best future course of action. The main project objectives are: Advance understanding of nutrient loading and circulation processes that shape NB hypoxia, and assess their relative importance; Continue and augment observation programs that generate products needed to identify and understand hypoxia trends during a period when significant changes in nutrient loading will occur; and Implement multiple modeling approaches to develop tools for (i) evaluating the response of hypoxia to alternative management scenarios and climate change, and (ii) enhanced predictive capabilities. An integrated suite of observations with multiple modeling approaches is included. A network of fixed-site stations will record time series of water properties (oxygen, salinity, temperature, chlorophyll fluorescence) that are used by the Rhode Island Department of Environmental Management (RI DEM) to designate impaired waters. Complementary spatial conductivity-temperature-dissolved oxygen (CTDO) surveys, also used by RI DEM, will characterize the geographic extent and spatial patterns of hypoxia. An updated nutrients budget will be calculated, as facilitated by continued measurements of standing stocks. Previous analyses suggest hypoxic event timing/severity is not closely linked to the biological and physical parameters presently being monitored, motivating a new program to monitor volume transport in the main passage that delivers coastal waters to and from the hypoxia-impacted upper bay and hence controls its flushing. This will be accomplished cost-effectively by installing a current profiler on a ferry, and will generate a real-time product potentially valuable for forecasting purposes. Observations of a suite of parameters will extend the data records to 10+ years and be particularly valuable to enhance the ability to isolate long-term trends from inter-annual variability recognized to be prominent. Modeling components are designed such that observations are available to constrain all parameters, and include (a) a hybrid ecological-hydrodynamic approach, in which simplified ecological parameterizations are applied in a small number of domains with ecologically-relevant sizes, while material exchanges among these coarse-scale domains are determined using dye tracking in a 3D hydrodynamic model with fully realistic forcing and high spatial resolution; (b) empirical exploration of the relationship between the timing and severity of hypoxic events and a broad range of biological and physical factors, in order to generate forecasts of three-day mean oxygen concentrations using the previous several weeks of observations. An annual workshop will continue ongoing interactions between researchers and representatives from several management and regulatory agencies, who will serve as a Management Advisory Group to provide guidance regarding research priorities.

Green Bay Hypoxia: Biogeochemical Dynamics, Watershed Inputs, and Climate Change


J. Val Klump (lead PI), Hector Bravo, Janes Waples University of Wisconsin at Milwaukee, Great Lakes WATER Institute and Dept. of Civil Engineering and Mechanics
Paul Baumgart, David Dolan,
Kevin Fermanich
University of Wisconsin at Green Bay, Dept. of Natural and Applied Sciences
David Lorenz, Daniel Vimont University of Wisconsin at Madison, Center for Climatic Research/Dept. of Atmospheric and Oceanic Sciences
John Kennedy Green Bay Metropolitan Sewerage District
Nicole Lyn Richmond Wisconsin Department of Natural Resources

Green Bay, Lake Michigan while representing only ≈7% of the surface area and ≈1.4% of the volume of Lake Michigan, contains one-third of the watershed of the lake, and receives approximately one-third of the total nutrient loading to the Lake Michigan basin as a whole.  With a history of hyper-eutrophic conditions dating back nearly a century, the southern portion of the bay behaves as an efficient nutrient and sediment trap, sequestering much of the annual carbon and nitrogen input within sediments that quickly become anaerobic.  Hypoxia within lower Green Bay and the Fox River has been a problem for decades and recent evidence suggests that hypoxia may be worsening, with the potential for “dead zones” and fish kills becoming more frequent and more extensive.
Climate change projections:  Climate change predictions for the Great Lakes region include warmer and more prolonged summers, increased precipitation and higher frequency of extreme events.  Higher temperatures increase organic matter decomposition rates, decrease oxygen solubility, and increase sediment oxygen consumption.  Increases in precipitation may enhance nutrient inputs in the absence of mitigation strategies to limit non-point source runoff, prolong or worsening hypereutrophy and hypoxia in the bay.  Climate change may also trigger indirect consequences like those observed in the summer wind field, decreasing flushing of the bay and increasing the retention of labile organic matter.
Scientific objectives:  1) Develop a data set of the temporal and spatial distribution of oxygen concentrations in Green Bay that will allow modeling the principle features of summertime hypoxia;  2) Expand the current integrative watershed approach for quantifying inputs of nutrients and suspended  sediments to the bay; and assess the efficacy of the implementation of land use best management practices throughout the watershed;  3) Develop and implement a high resolution 3-D coupled hydrodynamic and biogeochemical nutrient-oxygen model framework for the bay linked to the Princeton Ocean Model for Lake Michigan;  and 4) Assess the impact of future regional climate change projections based upon the assimilation and downscaling of an ensemble of 14 GCM’s being conducted by the Wisconsin Initiative on Climate Change Impacts for both mid-century and late century scenarios.
Collaborations:  This research is a collaboration among several university research groups within the University of Wisconsin System, including:  UW-Milwaukee Great Lakes WATER Institute, UW-Green Bay, Dept. of Natural and Applied Sciences, UW-Madison Center for Climatic Research, UW Sea Grant Program;  as well as other groups and stakeholders including:  public sector utilities, e.g., the Green Bay Metropolitan Sewerage District; governmental agencies, including the Wisconsin Department of Natural Resources and the U. S. EPA Region 5; and the Wisconsin Initiative on Climate Change Impacts.  This research effort will employ analysis of historical data, empirical measures of oxygen dynamics, and high resolution models of both watershed inputs and in bay biogeochemistry and hydrodynamics.
Management use:  Quantifying the link between nutrient inputs and hypoxia, and an assessment of the target levels of abatement needed to meet water quality goals, are essential outputs of this research.  The potential impacts of climate change on the biogeochemical behavior of the bay and on future nutrient loading will alter key baseline drivers in this system, but to a yet unknown extent.  Developing these linkages directly improves the capabilities of managers to devise more robust regulatory and non-regulatory mitigation strategies, defend those strategies to stakeholders, and more accurately estimate costs and benefits to water quality.

Shallow Water Hypoxia – Tipping the Balance for Individuals, Populations and Ecosystems


Denise Breitburg (lead PI) Smithsonian Institution Environmental Research Center
Timothy Targett, Charles Culberson University of Delaware
Bruce Michael, Michael Naylor Maryland Department of Natural Resources
Richard Batiuk U.S. Environmental Protection Agency Chesapeake Bay Program
Kenneth Rose Louisiana State University
Steven Giordano, Howard Townsend NOAA Chesapeake Bay Office

This project will investigate effects of diel-cycling hypoxia, and associated day-night swings in pH, in shallow waters where they occur, and as factors that may tip the relationship between nutrient loads and system-wide production of upper trophic level biota from positive to negative.  Low dissolved oxygen is an increasingly prevalent and severe perturbation that negatively affects growth, reproduction, and survival of exposed organisms. Understanding and predicting the effects of hypoxia on upper trophic level species at large spatial scales has been difficult, however, because of a number of mechanisms potentially mask or compensate for negative effects on fish and shellfish abundances and fisheries landings. In particular increased prey production in shallow waters may compensate for lost production in deeper hypoxic habitat.  Loss or reduced suitability of this productive shallow water refuge may therefore negatively affect fish and shellfish both within shallow habitat itself, and system-wide as the relative production of deep and shallow water habitats converge.  Accompanying diel-cycling pH may exacerbate impacts of hypoxia, and the combination of these factors may lead to more severe effects than predicted by lab experiments that examine effects of low oxygen in isolation.

The objectives of the proposals research are to: (1) determine the quantitative relationship between diel-cycling pH in shallow water habitats within the Chesapeake Bay system; (2) determine the exposure of economically and ecologically important species to diel-cycling hypoxia and co-occurring low pH in the field; (3) test the individual and interactive effects of diel-cycling hypoxia and diel-cycling pH on juvenile growth, mortality and reproduction of economically and ecologically important finfish and oysters, and on the acquisition and progression of the protistan parasite Perkinsus matinus infections in oysters; (4) Refine and use exposure-effects models to predict effects of diel-cycling hypoxia and pH fluctuations on fish and oysters under conditions experienced in Chesapeake Bay; and (5) Use spatially explicit food web models to predict, under a range of management scenarios, how shallow water diel-cycling oxygen and pH affect (a) system compensation for lost production resulting from seasonal bottom water hypoxia, and (b) sustainable yields of exploited species in Chesapeake Bay.  A suite of management-relevant data and predictive tools will improve the ability to predict effects of nutrient enrichment and management on living resources at local and regional scales, improve spatial targeting of ecological and fisheries restoration and water quality monitoring activities, and refine water quality goals as appropriate for shallow water habitat that serves a critical nursery function.  Close collaboration between PIs, and the project’s Management Partnership Team, and other regional managers, will help ensure relevance of research and translation of results into ecosystem and living resource management and restoration plans.

Modeling Hypoxia and Ecological Responses to Climate and Nutrients


Michael Kemp (lead PI), Ming Li, Elizabeth North

University of Maryland, Center for Environmental Science, Horn Point Laboratory

Walter Boynton, David Secor

University of Maryland, Center for Environmental Science, Cambridge Biological Laboratory

Domenic DiToro

University of Delaware

Katja Fennel

Dalhousie University

Coastal eutrophication and associated bottom water hypoxia are problems of growing proportions worldwide. Although in many estuaries water quality monitoring and modeling programs have been developed to assess and forecast ecological responses to nutrient loading, site-specific approaches and ineffective researcher-manager communications have limited their success. This project will produce robust science-based predictive tools readily implemented for any coastal system to simulate ecological responses to climate and nutrient input management.

The project combines:

  1. retrospective analysis of existing data on climate, nutrients, and hypoxia, with
  2. diagnostic assessment of mechanisms underlying observed ecological dynamics,
  3. simulation studies that develop numerical models to forecast and analyze water quality responses to climate and nutrient management, and
  4. habitat evaluation of the associated variations in size and quality of living space for selected fish and invertebrate populations.

Because of the existing rich data bases and active collaborations between researchers and managers, the partially-stratified Chesapeake Bay (CB) and the shallow well-mixed Delaware Inland Bays (DIB) offer ideal but contrasting study sites.

Information on variations in river flow, water temperature, and wind velocity will be used in conjunction with water quality monitoring data to produce statistical models (CART, GAM, ARMA) for quantitative interpretation of spatial-temporal patterns of water quality in relation to climate and nutrient loading variations at relatively coarse scales. A coupled model of physical circulation (ROMS) and biogeochemistry (RCA) will be used to analyze these data further and to improve quantitative understanding of mechanisms underlying observed hypoxia responses to climate variations at finer scales.

Adjoint data assimilation methods will be used for parameter optimization in the biogeochemical model, as implemented for a well-studied nutrient enrichment experiment (MERL). Simulation performance of the coupled ROMS-RCA model will be tested quantitatively by comparing model and data both for series of specific observations and for statistically derived functional relationships among key processes and properties. The coupled circulation-biogeochemical model, which is designed with open source-codes and flexible structures, will be readily transferable for implementation by other users in diverse coastal systems. Ensemble simulations, with alternative parameter sets and forcing climatologies, will provide confidence-limits to help scientists and managers interpret scenarios and forecasts.

Model simulations will include routine seasonal forecasts of hypoxia distribution and intensity in upcoming summer seasons based on spring climatic and ecological conditions and on average summer climatology. Annual and decadal scale simulations will also examine ecological responses to nutrient management scenarios under different climatic conditions. In addition, output from the coupled ROMS-RCA model will be combined with habitat suitability and bioenergetic algorithms for key fish and invertebrates to compute habitat quantity and quality as well as potential fish production. This project will be conducted by a team of ecologists, oceanographers and modelers working in direct collaboration with technical staff of resource management agencies (EPA, NOAA, DNR, DNREC), thereby facilitating transfer of results to CB and DIB managers. We will use teacher internships to engage K-12 educators and students into our research, developing friendly interactive websites for classroom applications.