We study spatial scale with several approaches to analyze hierarchy, components, and value of habitat dynamics. For example, we study hierarchical relationships of individual, population, community, ecosystem, and landscape, in which we attempt to predict the behavior and characteristics of each level using higher and lower levels of organization. We study three components of ecological scale in habitat use and predator-prey interactions: "Grain" (patch size), "Lag" (distance between patches) and "Extent" (distance the interaction is manifested). These scale elements may also depend on predator and prey densities. We compare "source" and "sink" subcomponents of metapopulations. We test habitat value using indicators of species diversity, abundance, indices of biotic integrity, and functional aspects (growth, survival). We have three on-going projects that assess these habitat interactions.
Nearshore Communities and Shoreline Development
Small fish (juveniles, minnows, killifish) and decapod crustaceans (e.g., juvenile blue crabs, grass shrimp) use nearshore shallow water (<1 m) as crucial habitat providing refuge from predatory and cannibalistic large fish and blue crabs. We study natural factors and human impacts that affect nearshore habitats. Natural shoreline habitats including marsh, forest and sandy beaches contribute to the refuge value by providing emergent vegetation, detrital resources, woody debris and gradual bathymetry. Human activities impact the refuge and nursery value of this habitat by shoreline development and erosion control with bulkheads and rock revetment that create deeper water at the water's edge, as well as destroying marshes and shoreline forests. This work is funded by the Smithsonian Environmental Sciences Program and SERC Fellowships Program.
Clam Metapopulation Biology
Macoma balthica is a dominant estuarine infaunal bivalve in Chesapeake Bay. It is a facultative deposit/suspension feeder, and is a major prey item for blue crabs and demersal fishes. We compare metapopulation dynamics among key habitats (sand vs. mud; upper vs lower bay; marsh vs non-vegetated shoreline). This research has been funded by NSF, Smithsonian Environmental Sciences Program, and NOAA.
Estuarine habitat quality is linked to environmental factors on the watershed and the down-stream water body. With funding from EPA, we are testing for indicators of this interactive continuum of habitats through a comparison of some 30 mesohaline subestuaries that differ in watershed land use (urban, agriculture, forest), shoreline development, and riparian characteristics. click here to learn more>>