Finite Volume Community Ocean Model (FVCOM) provides high spatio-temporal hydrodynamics to inform biogeochemical wetland-estuarine models.

Salt marshes are recognised as one of the most important intertidal habitats within the coastal-wetland interface and play a key role in the biogeochemical cycling of nutrients. The past few decades have seen an increase in human population and activity (agriculture, recreational, domestic). This has contributed to increases in nutrient loads, which have the potential to change marsh biogeochemistry and in turn affect the water quality of an estuary. This study makes use of a high-resolution Finite Volume Ocean Model (FVCOM) coupled with a biogeochemical model (the Integrated Compartment Model, or ICM). This approach makes for a powerful tool for understanding tidal marsh-estuarine ecosystem dynamics and riverine systems overall influence on water quality. FVCOM-ICM is being adapted to the Housatonic River, the second-largest sub-estuary of Long Island Sound (LIS). The addition of a drag marsh model and wetting/drying processes provide a realistic representation of the marsh hydrodynamics. Using an unstructured triangular grid enhances the resolution of temperature, salinity and water circulation patterns captured in the Housatonic River (including the Wheeler Marsh), as well as further offshore in the river plume. Model output and observed data are compared for hydrodynamic model validation and small-scale circulation features (e.g. the river plume) are examined. The continued progress to enhance parameterisation of the ICM model will provide (1) further insight into important processes governing marsh systems (e.g. denitrification), (2) advance our understanding of nutrient exchanges across the marsh-estuary interface, and (3) build the framework necessary for future upscaling of this coupled physical-biogeochemical marsh-estuary model to the entire LIS.