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Objectives ~~~~~~~~~~~~~~~~~
The objectives of this coupled-field and modeling research program are to 1) determine
the physical and biological conditions that cue oyster (Crassostrea virginica) spawning in the Choptank River, 2) identify the vertical gradients that cue oyster larval behavior, 3) develop, enhance, and validate a biophysical larval transport model of the Choptank River, 4) develop and link a demographic model to the larval transport model, 5) use the linked larval transport-demographic model to assess how environmental variability and habitat alteration influence oyster reef connectivity and population dynamics, and 6) apply findings and predictions to support oyster restoration and management efforts. Although this integrated program will focus on oysters, the scientific activities will result in a significant enhancement of our understanding of the interactions between physical conditions and other bivalves like soft clams and mussels.

Rationale ~~~~~~~~~~~~~~~~~
____Physical-biological interactions is a new discipline that investigates how the physics of water and the biology of marine organisms interact. These interactions are an important part of understanding fish and shellfish early life (eggs and larvae),the processes that influence their survival to become juveniles (juvenile recruitment), and the year-to-year changes in their abundances. This program builds on existing state-of-the-art models, tests and applies a new technology that will significantly advance our ability to investigate bivalve larvae in nature, and will generate new information about oyster early life that will enhance our understanding and prediction of their juvenile recruitment. In addition, this research will make quantitative links between larval transport and a full life-cycle population model. In doing so, it will provide improved understanding of the interrelationships between, and relative importance of, larval transport, reef connectivity, and adult growth, mortality, and spawning, and how these relationships are influenced by changes in environmental conditions and habitat alteration.
____This program will benefit society by providing new insights and understanding that will enhance fisheries management capabilities and improve our ability to understand and respond to the impacts of climate change. The numerical tools developed will have the resolution appropriate for helping to guide oyster restoration programs, locate optimal sanctuaries, and inform spatial management of oyster harvest. A PhD graduate student will be trained in field and numerical modeling research and the application of scientific findings for sustainable management of natural resources.

Methods ~~~~~~~~~~~~~~~~~
____In the field program, we will 1) train, test and validate a new system for bivalve larvae identification, and 2) apply it to understand oyster spawning patterns and larval behavior. We will use the Larval Identification and Hydrographic Data Telemetry (LIHDAT), designed by Scott Gallager and colleagues at Wood Hole Oceanographic Institution and manufactured by Advanced Habitat Imaging Consortium, Inc. The LIHDAT system uses polarized light to identify the birefringence patterns of shellfish larvae (pictured here):
(Image from Tiwari & Gallager 2003 Proc. 9th Inter. Conf. on Computer Vision)
After we train and test the system, we will collect water samples from the Choptank River and use the LIHDAT system to identify bivalve larvae in the samples. We will map the distribution of oyster larvae throughout the Choptank River and track patches of larvae as they are transported by the currents. We also will collect samples from different depths to better understand the vertical swimming behavior of bivalve larvae.
____In the modeling program, we will implement a high-resolution circulation model of the Choptank River using the Regional Ocean Modeling System (ROMS). We will link it to an oyster larval transport model and an oyster population model. All model components (circulation, larval transport, demographics) will be validated with observations from the field program as well as other ongoing monitoring programs (e.g., Maryland Department of Natural Resources Shellfish Monitoring Program). The linked larval transport-demographic model will be used to identify which factors influence spatial patterns in oyster abundances, which reefs are sources and sinks, and how environmental variability, habitat alteration, and potential climate change influence oyster populations.

Schedule ~~~~~~~~~~~~~~~~~
Year One (2009)
Model: Develop high resolution circulation model of the Choptank River
Laboratory: Train the LIHDAT system to identify bivalves native to the Choptank River

Year Two (2010)
Model: Validate circulation model; implement larval transport model
Field: Map bivalve larvae in the Choptank River during the oyster spawning season

Year Three (2011)
Model: Develop linked population and larval transport model
Field: Map bivalve larvae in the Choptank River during the oyster spawning season
Field: Sample larvae at different depths at the same location to identify the vertical gradients that cue oyster larval behavior (two 2-day fixed station time series)

Year Four (2012)
Model: Run, validate, and analyze coupled model simulations
Field: Map bivalve larvae in the Choptank River during the oyster spawning season
Field: Sample larvae at different depths at the same location to identify the vertical gradients that cue oyster larval behavior (two 2-day fixed station time series)

Year Five (2013)
Integration: Combine field data and model predictions to determine the connectivity and source/sink characteristics of each oyster reef.
Prediction: determine how the Choptank River oyster population is influenced by environmental variability and habitat alteration.
Application: apply results to support oyster population restoration efforts (this will be on-going throughout the project).
Dissemination: complete publications and release numerical models as open-source code so that findings/techniques can be applied to other regions in Chesapeake Bay and beyond.