Abstract
The objective of this study is to evaluate the effect of transparency on the change in eelgrass (Zostera marina L.) bed area in eutrophic coastal zone of the Hiroshima Prefecture between 1976-77 and 1999.
Eelgrass in the coastal areas where high deposition on leaves and steep slope (>5/100) were observed tended to colonize shallower zone than other coastal areas (29 sites: Denmark, Netherlands, USA and Japan) under the same lighting condition. In addition to transparency, deposition on leaves and steep slope seemed to limit the eelgrass distributions there.
Losses of some eelgrass habitats occurred even though transparency was same or increased, and at a few sites eelgrass bed increased without change in transparency. Thus, the transparency is not always responsible for the change in eelgrass bed. Although there were sites where the bed area changed in proportion to the change in transparency, the maximum depth limit was shallower than that estimated from transparency, or eelgrass habitat in shallow area disappeared significantly by other factors such as slope, deposition on leaves and burial.
