Large-Scale Comparison of Eelgrass Planting Techniques on the Potomac River

Project Start: 2003
Scheduled Completion: 2005
Primary Funding Recipient: Maryland Department of Natural Resources

There are many regions within Chesapeake Bay where habitat conditions are suitable for SAV growth, but are currently lacking vegetation, probably due to a lack of adequate seed or propagule sources. By identifying and strategically planting or reseeding beds in these areas, it is expected that these beds would serve as a seed source to greatly accelerate natural revegetation on a much larger scale. The lower Potomac River was chosen as the site for this project for two reasons. Despite recent improvements in habitat conditions, and historical evidence of very large eelgrass beds throughout the lower Potomac River, the river has not experienced a significant re-vegetation of SAV beds. Second, Maryland will be planting approximately 22 acres of SAV (eelgrass, redhead, and sago pondweed) at two sites on the lower Potomac in partial mitigation for loss of SAV associated with construction of the Woodrow Wilson Bridge replacement in the upper tidal Potomac River near Washington DC. Locating this eelgrass seeding project adjacent to these sites will allow for the completion of a large-scale restoration effort (up to 100 acres) and a direct comparison of the effectiveness of vegetative shoots versus seeds. Eelgrass seeding sites will be located adjacent to eelgrass vegetative shoots mitigation sites. Seeds will be hand broadcast by boat during the fall of 2003, and the spring and fall of 2004 and 2005. Spring seed work will be done using a modified version of the seed bag technique described by Pickerell. Fall broadcasting will be performed manually. The effect of seeding density and time of year for seed broadcasting will also be tested.

Spatially intensive habitat assessments (DATAFLOW) will be conducted twice per month throughout the eelgrass growing season. DATAFLOW is a shipboard system of geospatial equipment and water quality probes that measure water quality parameters from a flow-through stream of water collected near the water's surface. Temporally intensive habitat assessments will be carried out via continuous monitors (YSI 6600 EDS) located at each restoration site. Between the two techniques, we will be able to understand both the short- term variation in water quality and the site-specific differences in water clarity throughout the planting areas.

Comparisons between the effectiveness of eelgrass seeds and vegetative shoots will depend on close coordination between this project and those carrying out the mitigation project. Leads for both projects are committed to working cooperatively to ensure that methods and timing of field monitoring of shoots and seedlings will be coordinated as closely as possible. Pending availability of funding, a minimum of two years of monitoring will be conducted.