Quantitative Models Describing Past and Current Nutrient Fluxes and Associated Ecosystem Level Responses in the Narragansett Bay Ecosystem
Citation:
Rashleigh, B., H. Walker, T. Gleason, M. Abdelrhman, L. Charlestra, E. Dettmann, Peg Pelletier, S. Hale, G. Thursby, N. Detenbeck, D. Keith, S. Rego, S. Robinson, J. Grear, S. Ayvazian, AND M. Mazzotta. Quantitative Models Describing Past and Current Nutrient Fluxes and Associated Ecosystem Level Responses in the Narragansett Bay Ecosystem. U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-15/174, 2015.
Impact/Purpose:
An integrated modeling approach such as ours provides opportunities for considering a broader understanding of estuarine systems, including an assessment of unintended consequences and feedbacks. For example, the dynamics of sediment diagenesis plays a significant role in determining nutrient concentrations. The mechanistic nature of the hydrodynamic and water quality models, in particular, allow us the possibility of using these models for forecasting the results of future scenarios. The set of models can contribute to assessments of multiple stressors, and the relative importance of these, which is an important holistic view of the Narragansett Bay system.
Description:
Multiple drivers, including nutrient loading and climate change, affect the Narragansett Bay ecosystem in Rhode Island/Massachusetts, USA. Managers are interested in understanding the timing and magnitude of these effects, and ecosystem responses to restoration actions. To provide scientific support for nutrient management in Narragansett Bay, we developed a set of models based on past and current data for hydrodynamics, water quality, and ecology, calibrated to current conditions. We used linked mechanistic hydrodynamic and water quality models (EFDC/WASP), developed empirical approaches to quantitatively relate nutrient and dissolved oxygen concentrations to seagrass habitat (both bio-optical and seagrass predictive models), benthic macroinvertebrates, and fish; and applied a general model (the ECOPATH/ECOSIM model) for the foodweb. Our integrated set of models was generally able to reproduce observed data for the estuary and characterize scientifically valid patterns. Current modeling challenges include limited data availability for water quality and selected inputs, variability associated with invertebrate and fish populations, and issues of scaling for model linkage. We assessed the feasibility of using modeling for decision-making in the context of integrated nutrient management, with a goal of transferability to other Northeastern estuaries. While the models seem useful to answer questions related to Narragansett Bay, some aspects of this approach (i.e., the hydrodynamics and seagrass models) are more transferrable than others. Future directions include the testing of scenarios (e.g., land use change, habitat restoration, marine spatial planning), development of modeling approaches for zooplankton and shellfish, and the incorporation of economics.