Photo of Fox Creek marsh by Dr. Charles L. Gallegos

A Shallow-water Coastal Habitat Model for Regional Scale Evaluation of Management Decisions in the Chesapeake Region

A collaboration with the following other SERC labs:
Ecological Modeling, Photobiology and Solar Radiation, Biogeochemistry, and the Nutrient laboratory

The goal of this collaborative SERC project will be to develop a model focusing on the response of shallow tributary embayments and small tidal creeks of Chesapeake Bay to multiple, interacting stressors such as climate-related flow changes, UV-B, CO2, and land use changes. The end points for this model will be those indicators currently being proposed for use by managers, namely, chlorophyll, water clarity, and dissolved oxygen. Our approach will combine GIS (geographic information system) analysis of landscape features with mass-balance modeling in a Monte Carlo framework that will predict the expected distribution of indicator values within tributaries and tidal creeks in the major salinity zones of the Bay.

Project Details:

Management decisions to protect estuaries are being made in the context of unprecedented environmental changes. For example, increased ultraviolet (UV) radiation, especially the damaging UV-B, has been documented and is expected to continue even at temperate latitudes. The carbon dioxide concentration of the atmosphere rose by 30% in the 20th century and is continuing to climb at a rate of about 1% per year. The effects of CO2 and other greenhouse gasses on global climate change are highly uncertain, but alteration of rainfall and runoff patterns are considered likely. Interactions between altered flow regimes and changes in land use patterns will have consequences for the delivery of sediments and nutrients to estuaries. Projecting the efficacy of management actions must proceed on the basis of predictions from mathematical models, since experimental manipulations cannot be made on the relevant scales.
However, the effects of simultaneous, multiple stressors have not previously been incorporated into models of ecosystem processes.

Our modeling efforts will focus on shallow tributary embayments and small tidal creeks of Chesapeake Bay. This emphasis reflects our belief that the ecological importance of shallow systems far exceeds their volumetric contribution to the bay. Their importance derives from the many hectares of potential habitat for submersed aquatic vegetation created by their highly indented shorelines, and from their role as spawning and nursery grounds for finfish and as refuge habitat for juvenile fish and crabs. The end points for our model will be those indicators being used as de-listing criteria for Chesapeake Bay, namely chlorophyll, water clarity (diffuse attenuation coefficient) and dissolved oxygen.

We conceive of shallow sub-estuaries as part of a continuum of aquatic ecosystems linking watersheds with coastal marine waters. We will represent shallow sub-estuaries as well-mixed compartments that receive and process inputs from their local watershed, and exchange materials at their seaward boundaries. Mass balance modeling techniques will be employed for the model structure, with rate processes dependent upon interactions amongst stressors. The stressor interactions that we will incorporate vary through the coastal landscape. In the watershed, we will consider interactions between climate-induced flow alteration with changes in land use, as they impact delivery of nutrients and sediments to the estuary. In wetlands we will consider the interactions between rising CO2 and wetland distribution on delivery of dissolved organic matter. In the estuary we will model interactions amongst nutrients, sediments, dissolved organic matter, and UV-B on plankton growth and light penetration. We will use a Monte Carlo approach that will facilitate investigation of alternative management scenarios, and predict cumulative distribution functions of the de-listing criteria for comparison with reference curves which are currently under development.

Supplemental Keywords: ecological effects; marine science; estuary; modeling; ecology; hydrology; Chesapeake Bay.