Abstract
Vertical changes in sandy bottom level, wave height, and current velocity were measured inside and outside a dense eelgrass (Zostera marina) bed. Waves of 0.9m eroded the sandy bottom by up to 0.12 m outside the dense eelgrass bed but did not cause erosion inside the bed. Rough waves caused rapid erosion but gentle waves restored the original sandy bottom levels. Shield's number, an indicator of the instability of sea bottom sediment, was larger inside the dense eelgrass bed than outside. These results showed that the dense large scale eelgrass bed functioned to stabilize the bottom sediment and prevent the sandy bottom from eroding. In addition, it appeared that this function was made possible by the density of eelgrasses and a sheet of subterranean stems.
