An effective transplanting technique using shells for restoration of Zostera marina habitats

Significant declines in seagrass coverage have occurred in many parts of the world. In recent decades, transplanting projects for seagrass restoration at die-off areas have been attempted, but most current seagrass transplanting techniques are cost and labor intensive. We have developed a new seagrass transplanting method in which oyster shells are used as an anchoring device, and does not require SCUBA diving for sub-tidal planting. Here, we tested the shell method for feasibility and efficiency in large-scale seagrass restoration. Planting units consisting of two Zostera marina shoots anchored to one oyster shell were dropped from a boat to settle on the sediment at the test site. Four transplanting trials were conducted throughout the experimental period (December 2003, January, February, and November 2004) in Koje Bay on the southern coast of Korea. Eelgrass shoots planted using the shell method successfully established at the test areas, and the survival rates of transplants were comparable to those obtained using other common planting techniques. The transplant shoot density declined during the first 2-3 months following transplantation due to the initial transplant shock, and then surviving shoots became established at the sites and produced new lateral shoots after these periods. Plant size and leaf productivity of transplants 7 months post-transplanting were similar to or exceeded those of pre-existed shoots, suggesting that the physiological status of transplants is similar to that of natural population after 7 months. Because the shell method did not require workers to be in the water, the method was cost and labor effective. Additionally, given that shells originate from marine environments, the shell method did not leave any hazardous materials in the transplanting areas after restoration.