Abstract
The objective of this study is to investigate the effect of belowground biomass reduction on the stability of eelgrass shoots in sediment in order to clarify the factors responsible for the outflow of eelgrass shoots even with little wave disturbance in Nagatsuraura Bay, Japan. We also investigated environmental conditions in the vicinity of eelgrass with and without root death. Loss of roots without dying-back symptoms led to a decrease in the stability of eelgrass shoots in sediment, and allows for the uprooting of shoots with little disturbance. The decay of healthy root biomass of eelgrass was associated with high sulfide concentration in sediment and/or low photosynthetic activity. In sulfide concentrations between 0.5mg g D.W.-1 and 1.5mg g D.W.-1, eelgrass with high photosynthetic activity tended to display fewer stunted roots compared to shoots for which photosynthetic rates were low. This result suggests that eelgrass with high photosynthetic activity seemed to prevent sulfide intrusion by supplying oxygen to belowground tissues to maintain an oxic microsphere around the roots and re-oxidizing it to a harmless sulfate.
