Great Bay’s Underwater Grasses
Seagrasses are a keystone of healthy estuaries here in New England and throughout the world. They are rooted, flowering perennial plants that grow underwater and are typically subtidal. With origins on land, seagrasses evolved to survive in shallow coastal waters about 100 million years ago. They are distinct from marsh grasses that grow in the intertidal zone, and from dune grasses which generally grow along beach dunes above the high tide line. Eelgrass (Zostera marina) is the dominant seagrass in Great Bay. When healthy, it forms dense underwater meadows that provide many benefits to bay organisms and us, including producing great quantities of oxygen that many marine creatures need to thrive, provide excellent physical habitat for young fish and shellfish, improves water quality by absorbing excess nutrients, and increases water clarity by filtering sediments. These are but a few of the important functions provided by healthy eelgrass beds that make places like the Great Bay Estuary such unique and valuable coastal ecosystems.
A recently completed paper titled “A Case for Restoration and Recovery of Zostera marina L. in the Great Bay Estuary” written by a collection of local scientists and managers, including our Research staff, highlights recent population trends and the current state of eelgrass science in Great Bay. In past few decades, our Bay has lost over half of its eelgrass due to changing precipitation and temperature patterns, increases in human development, and declining water quality. With much of Great Bay failing to meet state water quality standards, many municipalities in the watershed recently invested in upgrades to their wastewater treatment plants to help reduce one of the main sources of nutrients coming into the Bay. While there is more work to be done to improve water quality, there are indications that recent reductions in nutrients, particularly nitrogen, are creating conditions more favorable for eelgrass growth in certain areas. The authors of this paper believe that eelgrass recovery may be accelerated with targeted restoration efforts, and highlight the process of selecting areas of the Bay most likely to succeed as well as providing an in-depth look at proven restoration practices. Repopulating eelgrass itself will further enhance water quality through nutrient take up and sediment filtering, and also further the understanding of processes affecting eelgrass survival and growth, with the incorporation of focused research and monitoring, both ultimately improving the health and resilience of Great Bay.
-Chris Peter, GBNERR Research Coordinator