Influence of volcanic ash sediments on spore adhesion of the red alga Gelidium elegans from the coastal seabed around Miyakejima Island, Japan

摘要

The populations of red alga Gelidium elegans along the coast of Miyakejima Island were severely damaged by a volcanic eruption in 2000. The effect of this volcanic eruption has been long lasting, and populations of this red alga still have not recovered. We investigated the effect of seabed sediment particles derived from volcanic ash on the substrate adhesion of G. elegans spores. The analysis provides evidence that increasing amounts of sediment particles result in lower adhesion rates of G. elegans spores, and that smaller sediment particles have a greater influence on adhesion. The amount of seabed sediment particles around Miyakejima Island was 9.3–1815.4 mg/cm2. This amount has changed greatly from year to year. The adhesion rate of G. elegans spores in water around Miyakejima Island was 0 % at all points in 2008 and 2010, but it was estimated as 6.3–38.6 % in 2009. These results suggest that there is significant inhibition of algal spore adhesion by seabed sediment particles derived from volcanic ash around Miyakejima Island.