Bio-physical Interactions in the Turbidity Maximum, BITMAX

An interdisciplinary study is proposed to investigate fundamental physical and biological process in the Estuarine Turbidity Maximum (ETM) of Chesapeake Bay. ETM zones located in the upper reaches of estuaries, near the interface between salt and fresh water, are known to entrap fine sediments and to entrap or aggregate zooplankton and early-life stages of fish. In Chesapeake Bay, a well-defined but poorly understood ETM occurs in the upper Bay. It is hypothesized that the ETM entraps sediment particles and planktonic organisms which in turn support enhanced zooplankton production and growth and survival of young anadromous fish. The proposed research will characterize constituents and evaluate processes operating in the Chesapeake ETM, including sediments and organisms that are of major ecological significance in the Bay. A key species in the ETM is the copepod, Eurytemora affinis, which is a major food of larvae and juveniles of anadromous fishes (striped bass, white perch, shads, river herrings).

The proposed research is a three-year effort, including two years of field observations in the upper Chesapeake Bay. Principal Investigators and collaborators include physical oceanographers, zooplankton ecologists, fishery ecologist, and modelers. Three seasonal cruises in the year 2001 and 2002 are proposed. Circulation features, salinity structure, tidal displacements, sediment resuspension and organism distributions will be measured from the research vessel and from moorings in the ETM. Zooplankton, fish eggs and larvae, and juvenile fish will be collected and their distributions evaluated with respect to the ETM.

The proposed research also includes a diagnostic modeling framework to explore the physical and biological dynamics of the ETM of partially mixed estuaries. Models will include numerical circulation, sediment transport, biological particle-trajectory, and individual-based population components. The model will be used in parallel with the field investigations to examine which processes are most important to explain observed distributions of sediments, zooplankton and fish in the ETM, and to help guide the field investigations in the study.

Results of this research will add substantially to knowledge of estuarine dynamics and features that support trophic transfers of materials and energy in estuarine communities. It is hypothesized that trophic transfers are enhanced in the ETM and that repoductive successs and recruitment of anadromous fishes is dependent upon linkages between estuarine physics and organism behavior in the dynamic ETM feature. In addition to expanding knowledge of fundamental estuarine processes, results will be useful for management of resources in Chesapeake Bay and other estuaries, which are challenged by anthropogenic impacts. The project will contribute to development of human resources by supporting graduate and undergraduate students, who will receive training in oceanography, ecolgoy, and modeling as they prepare for professional careers in marine and estuarine science.