Abstract
To examine the optimal season to set spore bags for Gelidium elegans, a test of spore release by using the spore bag method was conducted at two sites at Izu-Oshima Island. Two at each site, four net bags, in which mature G. elegans were placed and each with a float were set every month from October 2009 to December 2010. In addition, four net bags, without mature G. elegans, were set every month as a control at one site. The mean density of Gelidium spores that attached on spore collectors (glass slides) was significantly greater in the spore bags than that in the control, and increased from July to October at both sites. From these, we concluded that the period was the optimal season to set spore bags for G. elegans. The thalli of G. elegans were observed on the concrete blocks to which spore bags were tied at both sites. However, at one site, the thalli of G. elegans did not grow. We compared the environmental conditions of the two sites, there was a significant difference in the amount of sedimentation. It is thought that sedimentation is an important environmental factor in the growth of G. elegans.
