Seasonal changes in Zoanthus spp. in the infra-littoral zone at Taisho Lava field, Sakurajima, Kagoshima, Japan

Changes in Zoanthus spp. cover and polyp number were recorded by transect survey at Taisho Lava Field, Sakurajima, Kagoshima, Japan (N31 degree -35', E135 degree -35') for 30 months between May 1980 to October 1982. In addition, lab experiments were conducted to investigate changes in polyps, Zoanthus' gonads and zooxanthellae number at different seawater temperatures. Our results indicate that Zoanthus polyps grow during summer and autumn, and experience a decrease in size during winter and spring. Polyps close during periods with low winter temperatures, and zooxanthellae activity and concentration also decrease, perhaps due to the winter growth in many types of algae above polyps and the appearance of diatoms on polyps themselves. In addition, volcanic ash from the nearby active volcanic cone of Sakurajima also has a negative effect on Zoanthus polyps.