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.
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
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.
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.
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
See maps of restoration locations on the
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