The ocean

We propose a coordinated program of field and numerical experiments to examine processes that control the fate and transport of nutrients and chemical contaminants in the Hudson River plume, a plume that emanates from one of the nations most urban estuaries -the New York/New Jersey Harbor complex. Urban estuarine plumes represent a major pathway for the transport of nutrients and chemical contaminants to the coastal ocean. However, the fate and transport of this material is controlled not only by the plumes dynamics but also by biological and chemical processes that are coupled to the dynamics of the plume. By conducting a series of dye experiments featuring continuous underway chemical and biological sampling with a state-ofthe-art towed vehicle within the well sampled framework of an operational ocean observatory, we will be able to distinguish between physical processes that transport/mix material in a buoyant plume from biological and chemical transformation processes. This will allow us to quantify biological and chemical interactions in a Lagrangian perspective, and provide a means to assess their importance in determining the fate and transport of nutrients and chemical contaminants in a buoyant plume. This program will contrast the response of physical, biological, and chemical processes in the Hudson plume during upwelling and downwelling conditions. We hypothesize that cross-shelf transport of material is determined not only by Ekman transport and diapycnal mixing, but also by biological and chemical processes all of which differ between upwelling and downwelling conditions. For example, a vertically thin plume during upwelling conditions will have enhanced light levels, thus promoting biological production and potentially increasing the rate that chemical contaminants enter the food chain. In particular, we will quantifiably relate (a) biological production rates, (b) the bioavailability and bio-accumulation of metals, and (c) chromophoric dissolved organic matter (CDOM) photobleaching rates within the plume to the physical characteristics of the plume, such as plume thickness, optical depth, and mixing rates. An ocean observatory will facilitate interpretation of the dye study by placing the Lagrangian surveys in context with shelf-wide observations from satellite imagery, surface currents and far-field subsurface hydrography. The observatory will be augmented by a cross shelf array of moored instruments to provide detailed estimates of subtidal circulation, stratification and Reynold stresses. Finally, data-assimilative numerical simulations will provide high resolution and realistic hindcasts of the coastal ocean during the field experiments. Modeling will pioneer the assimilation of dye-tracer data into a 3-D coastal circulation model and guide future efforts to assimilate other tracers into circulation models with complex sources and sinks. Coupled physical/biological model hindcasts will be used to interpolate observations in space and time for interpretation, and to test turbulent and biological parameterizations. Our study will determine the geographic extent and biological impact of contaminants in the plume along the New Jersey coast and Middle Atlantic Bight. Results will improve our ability to predict the fate and transport of contaminants and the rate that they enter the base of the food chain in the coastal ocean. Quantifying contaminant uptake into the base of the coastal ocean food chain is the first step in predicting contaminant bioaccumulation at higher tropic levels. Finally, episodic nutrient inputs from the plume have been linked to coastal phytoplankton blooms and may drive recurrent low dissolved oxygen levels in this region. Results from this study could guide future strategies for sewage disposal for New York City. This program will provide traditional research and thesis opportunities for a state-funded Ph.D. program and NOAA-funded undergraduate internships. Moreover, it will provide focus for the first 5 years a new Masters in Operational Oceanography program initiated in 2002 by project PIs. Finally, ongoing collaboration with the Mid-Atlantic Center for Ocean Science Education Excellence (COSEE) will be strengthened by adding components on biological and chemical processes in buoyant river plumes. COSEE integrates oceanographic research and education programs to audiences that include coastal managers, K-12 teachers and their students--especially underrepresented groups in the marine science.