UMCES ChesBay Plume

This proposed study integrates observational, experimental and modeling approaches to study the effects of the Chesapeake Bay plume on benthic biomass, diversity, organic matter processing and nutrient fluxes within the inner shelf (Fig 2). We’ve identified four key Objectives that we will accomplish to address the study hypotheses. For Objective 1, we will conduct two full years of field sampling of water column and sediment conditions, nutrient concentrations, and benthic community composition at sites in the Chesapeake Bay plume region. This field design allows quantification of intra- and interannual variability of response and predictor variables. Objective 2 is to quantify spatial and seasonal changes in benthic community structure and secondary production as indexed by biomass, biodiversity and community composition. At a subset of our observational locations, we will execute Objective 3, a series of targeted laboratory experiments to test the differential assimilation of labile and refractory organic matter by benthic fauna inside, at the front, and outside of the plume. We will simultaneously measure sediment-water exchanges of nutrients and oxygen to associated patterns of benthic structure and assimilation rates to nutrient processing and metabolism. Objective 4 is to develop and validate a 3-D hydrodynamic numerical model to provide temporally-integrated estimates of plume conditions (e.g., salinity, temperature, organic matter deposition rates, near-bed physical disturbance) during the observational period. Finally, we will use the observational data and model outputs in concert to test our hypotheses and identify statistical relationships between plume influence and benthic community structure, diversity, productivity, and organic matter processing. Field cruises will be conducted seasonally (4 per year) for 2 years aboard an assigned UNOLS vessel along the Virginia inner continental shelf and just within the Chesapeake Bay mouth. Cruises will occur in the spring, summer, autumn, and winter each year to capture annual cycles of primary and secondary production (Objective 1). Each cruise, we will use a combination of underway and stationary sampling gear to collect biological and environmental data from sites ranging from c. 5–20m inside, outside and at the frontal edge of the Chesapeake Bay plume (Fig. 4A). A series of shipboard experiments will be used during all four seasons of the second field year to test hypotheses regarding spatial patterns in trophic assimilation and biogeochemistry.