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DNR Continues Bay Grass Restoration Efforts with Eelgrass Seed Dispersal in the Patuxent and Potomac Rivers

December 2005 - The Department of Natural Resources (DNR) Resource Assessment Service recently completed a third season of eelgrass seed dispersal in the Patuxent River and a second season in the Potomac River.

A photo of DNR's Resource Assessment Service biologists completing a third season of eelgrass seed dispersal in the Patuxent River and a second season in the Potomac River. Bay grasses (also known as submerged aquatic vegetation, or SAV) are critical to a healthy Chesapeake Bay. They provide important habitats for young fish and crabs, serve as food for waterfowl, help protect shorelines from erosion, keep water clear, consume excess nutrients, and add oxygen to the water. Excess nutrients (mainly nitrogen and phosphorus) and sediment resulting from human activities cloud the water and harm bay grasses by preventing sufficient sunlight from reaching the plants.

Reducing the amount of nutrients and sediment in Chesapeake Bay is the single most important action we can take to restore bay grasses. DNR is working on numerous fronts to accomplish this. In addition, DNR is continuing efforts to plant or seed bay grasses on a large scale in strategic locations to help achieve the state’s restoration goals.

DNR has long recognized the need for a large-scale bay grass restoration approach. There are areas of the Bay where water quality has improved sufficiently to support bay grasses, yet a lack of seeds prevents recolonization of these areas. Establishing large beds using seeds collected from healthy beds elsewhere could lead to vigorous natural revegetation in adjoining areas.

a photo of a mechanical harvesting boat.Using a mechanical harvesting boat, DNR biologists collected eelgrass reproductive material from Tangier Sound from May 23rd until June 9th, 2005. The seed material was transported to DNR’s Piney Point Aquaculture Facility where it was held through the summer in large tanks to allow for the seeds to separate from non-seed material.

Seeds were held until water temperatures dropped below 15 oC (59oF), suitable conditions for seed germination. A mechanical seed sprayer, mounted to a boat dispersed seeds at the rate of 10 minutes/acre. A total of 901,500 seeds were broadcast over 7.5 acres at three locations on the Patuxent River in August and again in November. In the Potomac River, 400,000 seeds were dispersed across 2 acres at three sites on the Potomac River in November. When water temperatures begin to increase in the spring, the eelgrass growing season begins. At this time, DNR divers will survey these areas to quantify the successful recruitment of eelgrass seedlings.
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In 2003, approximately five acres were seeded in Maryland. Increased collection efforts in 2004 resulted in a total of 36.25 acres being seeded at four sites on the Patuxent River and three sites on the Potomac River.

In addition to these seed broadcast efforts, DNR utilizes a buoy-deployed seeding system. A portion of collected reproductive seed material is prepared for immediate deployment in the spring. Mesh seed bags are filled with freshly harvested reproductive material, attached to cinderblock anchors, and deployed in a grid pattern covering a predetermined restoration area. In June, an additional 4,510,000 seeds covering 11.25 acres were broadcast on the Potomac River using this method.

Read more about MD large scale eelgrass restoration efforts.

See maps of restoration locations on the Patuxent and Potomac Rivers.

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