Collaborative Research: Larval Transport in a Coupled-Estuary-Shelf System: A Modeling Study

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This project will investigate the interactive effects of advection, mixing, organism behavior and environmental variability on larval transport in a coupled-estuary-shelf system using a theoretical approach, and the blue crab, Callinectes sapidus, as the model organism. Although previous research on larval transport has focused on export and re-entry to an estuary, there is a critical need to systematically examine the relative importance of multiple factors on the regional-scale exchange of larvae between estuaries and on recruitment variability. Numerical circulation models and particle-tracking algorithms have matured to the point where they are ready to address these problems. Investigators will use a coupled hydrodynamic-particle tracking model to systematically isolate and evaluate the effects of advection, mixing, organism behavior and environmental variability, and to integrate their complex and nonlinear interactions. Observed wind- and flow-driven circulation patterns will be simulated with a computationally tractable semi-idealized hydrodynamic model of the Middle Atlantic Bight. Particles within the numerical model will simulate blue crab early-life stages using the extensive information available from field investigations and laboratory behavior studies in this region. This is the first modeling effort that systematically focuses on the complex interactions between advection, mixing, organism behavior and environmental variability in a 3D numerical model that includes the latest understanding of sub-grid scale turbulent processes, vertically resolved blue crab larval behavior, and the ability to examine exchange between estuarine systems. Understanding the cause of recruitment variability and the strength of connections between coastal populations is a critical avenue of research for the recreationally and commercially important blue crab. The blue crab fishery is a valuable resource whose sustainability is currently in question in Chesapeake Bay. Understanding the physical processes that generate recruitment variability, and the degree of interconnectedness of estuarine populations, will help managers make more informed decisions for maintaining a sustainable blue crab fishery. Although focused on blue crabs, research results will be address fundamental, universal questions about factors that control large-scale transport of planktonic larvae on continental shelves, their return to nursery areas, and potential for exchange between estuarine systems. In addition to enhancing our understanding of the complex factors that affect larval transport and recruitment, this research program has a strong education and outreach component, including development of an interactive web page. One undergraduate summer student will gain numerical modeling and data analysis training. Also, one teacher Fellow will gain experience working with scientists and translating research results into lesson plans. The investigators involvement in the MA-COSEE program, the mentoring of a teacher Fellow, and development of a web page will promote direct interaction between scientists and educators and enable broad dissemination of research results.