Resilience and Positive Feedbacks: Water Quality Management and Eelgrass Health in the Great Bay Estuary - NERRS/NSC(NERRS Science Collaborative)

An interdisciplinary effort to examine eelgrass health has increased trust among partners and inspired ideas for new management strategies by municipalities and state agencies.

The Project

Eelgrass (Zostera marina) has been declining in Great Bay Estuary, New Hampshire over the past 20 years. Eelgrass has long been considered an indicator of estuarine health since declines in its distribution usually signal detrimental change in water quality. The sustained decline in eelgrass in Great Bay led the Environmental Protection Agency (EPA) to issue a Total Nitrogen General Permit in 2020 to curb both point and nonpoint sources of nitrogen (N) input in the Bay. Thanks to significant upgrades to wastewater treatment plants, nitrogen inputs have been declining. This project sought to determine whether those reductions improved eelgrass health or resulted in positive feedback that enhanced the resilience of eelgrass in Great Bay Estuary.

Building on existing regional collaborations, this project explored connections between eelgrass health, water quality, and water flow patterns in Great Bay. The project team combined hydrodynamic modeling and new field observations to examine potential stressors of eelgrass, including water residence time, nitrogen loading, in situ nitrogen processing, sediment dynamics, and light availability. A Project Advisory Committee made up of individuals from 14 organizations was formed to provide input to the project team and to ensure results were relevant, trusted, and useful within the current management context.

The project's hydrodynamic modeling found that Great Bay may be more sensitive to nitrogen loading than previously thought, because water can "reside" in the Bay far longer than expected. The project results also emphasized the need to prioritize sediment management along with nitrogen management. The project produced a wealth of resources, including a comprehensive technical report and an interactive story map. Project outcomes are directly informing adaptive management plans developed by communities, as well as future modifications to the EPA permit requirements. The momentum and funding from this project has also inspired several educational products associated with Great Bay NERR, including a new eelgrass exhibit, traveling education trunks for teacher classrooms, and a "Teachers on the Estuary" Workshop focused on eelgrass.

The Impact

Built a shared understanding among regional partners of Great Bay hydrodynamics and the factors that influence eelgrass health in Great Bay.

Jointly developed a foundation for further discussions on nitrogen and sediment management, and for the future development of a Total Maximum Daily Load (TMDL).

Inspired ideas for improved nitrogen monitoring protocol for municipalities and state agencies.

Increased trust in best available science of eelgrass and deepened collaborative relationships.

Increased interest and literacy about estuarine health amongst families in the watershed.

Project and Technical Lead

William H. McDowell, University of New Hampshire, bill.mcdowell@unh.edu

Collaborative Leads

Cory Riley, Great Bay NERR, cory.a.riley@wildlife.nh.gov

Lynn Vaccaro, Great Bay NERR, lynn.e.vaccaro@wildlife.nh.gov

The distributor does not assume liability.

None

Cite this dataset when used as a source: NOAA retains the right to analyze, synthesize and publish summaries of the NERRS/NSC data. The NERRS/NSC retains the right to be fully credited for having collected and process the data. Following academic courtesy standards, the NERR site where the data were collected should be contacted and fully acknowledged in any subsequent publications in which any part of the data are used. The data enclosed within this package/transmission are only as accurate as the quality assurance and quality control procedures that are described in the associated metadata reporting statement allow. The user bears all responsibility for its subsequent use/misuse in any further analyses or comparisons. The Federal government does not assume liability to the Recipient or third persons, nor will the Federal government reimburse or indemnify the Recipient for its liability due to any losses resulting in any way from the use of this data. Requested citation format: NOAA National Estuarine Research Reserve System (NERRS) Science Collaborative(NSC).

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This information is detailed within the project links.

This information is detailed within the project links.