Abstract
The objective of this study is to clarify the effect of light reduction by sediment deposition on leaves and sand movement on eelgrass distribution for obtaining fundamental knowledge on the formation of the eelgrass (Zostera marina L.) habitat. We investigated light regime and sediment deposition on leaves near the lower edge of an eelgrass bed, and monitored sand movement and transplanted eelgrass in an unvegetated site near the higher edge. The average light intensity through sediment deposition on eelgrass leaves was estimated to be approximately 3 E·m-2·d-1 at a low depth limit. As sediment deposition on leaves was 0.7 mg·cm-2 <, the light intensity required by eelgrass might be 4 E·m-2·d-1 <. Sand movement at the unvegetated site ranged from -10 cm to 12 cm and was more unstable than that at a natural site. Scouring for two months reached up to 10 cm, and seedlings disappeared at the unvegetated site near the higher edge. However, the number of vegetative shoots in the unvegetated site steadily increased. These results suggest that vegetative shoots can survive within 10 cm washouts and the growth of eelgrass near the higher edge of an eelgrass bed is restricted to vegetative reproduction.
