Photo: Recovery of eelgrass, Virginia, USA after sowing with eelgrass seeds. source: Orth et al. Seed addition facilitates eelgrass recovery in a coastal bay system. Mar Ecol Prog Ser. Vol. 448: 177–195, 2012
Eelgrass positively impacts on the marine ecosystem. So far, efforts to restore eelgrass have primarily focused on reducing nutrient loads from land. However, eelgrass has not responded directly to the declining nutrient inputs and restoration is happening much slower than expected. In some coastal areas, there is strong evidence that eelgrass will fail to establish in the foreseeable future because seabed conditions have changed as a result of previous high nutrient inputs or because of a lack of sufficient eelgrass seed populations.
Eelgrass restoration has been attempted in many areas throughout the world. In Denmark, it has been tried on a small scale in the Limfjord and Vejle Fjord. For almost all the projects, restoration attempts have concentrated on moving entire plants to a new area. This technique is very labor intensive and large-scale restoration has so far not been very successful.
Breakthrough with new technology
The latest and very promising results come from the US East Coast near Wasington DC, Chesapeake Bay, where Virginia Institute of Marine Science (VIMS) over a number of years have developed a new technique for harvesting and broadcasting eelgrass seeds. This must be regarded as a definite breakthrough for large-scale restoration. For the first time it has been shown, that it is possible to restore eelgrass to an area with widespread and resilient eelgrass meadows.
The project will develop techniques for harvesting, sorting, storing and broadcasting eelgrass seeds on a large scale.
The techniques required for successful large-scale restoration are:
– Construction of mechanized eelgrass seed harvester with limited impact on the harvested eelgrass meadows
– Seed separation and storage in tanks under adequate environmental conditions that maintain seeds viable and control the timing of germination;
– Seed preparation/germination and diver assisted or mechanized large-scale seed broadcast and/or seedling planting in selected estuaries
– Continuous monitoring the development of planted eelgrass, associated flora and fauna, and water quality parameters (nutrients, turbidity and light penetration) during the following years.
Costs of restoration and protection actions will be examined by balancing the estimated costs of protection of existing eelgrass habitats and restoration of new eelgrass habitats against the gains derived from ecosystem services provided by these habitats.
It is anticipated that the industrial partners at the end of the project will have the technical and knowledge capacity for submitting commercial offers on eelgrass restoration projects covering the whole process from seed harvesting to insuring seedling success.