Resilience and Positive Feedbacks: Water Quality Management and Eelgrass Health in the Great Bay Estuary

  • Margaret A. Davidson Fellow monitors eelgrass heath in Great Bay by assessing percent cover within randomly placed quadrats. Photo credit: Chris Peter.

    Margaret A. Davidson Fellow monitors eelgrass heath in Great Bay by assessing percent cover within randomly placed quadrats. Photo credit: Chris Peter.

The Great Bay Estuary, on the border of New Hampshire and Maine, is currently listed as nitrogen impaired, largely based on decreases seen in eelgrass habitat. Loss of eelgrass habitat resulted in a 2020 U.S. EPA “Great Bay Total Nitrogen General Permit,” focused on reducing nitrogen loading from 13 communities with Wastewater Treatment Facilities but also offering options on how to control nitrogen inputs through nonpoint source controls. Gaps in understanding of how eelgrass responds to changes in water quality limit the management tools available for ensuring eelgrass health. The New Hampshire Department of Environmental Services (DES) and permitted municipalities are looking to their partners, such as Great Bay NERR and the Piscataqua Region Estuaries Partnership (PREP), to provide critical scientific insights needed to meet the new permit requirements.

This project will explore whether nitrogen reduction actions have improved eelgrass resilience and the role that initial eelgrass recovery could play in further reducing the impacts of nitrogen and other stressors. The project combines hydrodynamic modeling and new field observations to delineate the relationships among nitrogen loading, in-situ nitrogen processing, sediment dynamics, light, and eelgrass resilience. Outputs include habitat connectivity estimates, likely stressor-response scenarios, charrettes, education curricula, and associated reports and presentations. Building on existing regional collaborations and efforts to link the science with decision making, this work will directly inform the adaptive management plans developed by communities, as well as future modifications to the EPA permit requirements.