Succession of Seaweed Communities on Artificial Reefs in Tei, Tosa Bay, Japan.

Abstract

A total of 18 artificial reefs (3 tons each of concrete trapezoid blocks) were placed in Ecklonia and Sargassum community on the gravelly patch about 7m in depth on the coast of Tosa Bay. The quantitative survey of seaweed community was carried out on the artificial reefs for 3 years. Colpomenia sinuosa dominated 1 month after their placement, but disappeared 3 months later. A total number of 19 species including Sargassum siliquastrum and S. micracanthum, Ecklonia cava and Corallina spp. were identified after 11 months and then the number of species was stabilized. The average of seaweed biomass was about 4, 000g wet weight m-2 from 17 months to 28 months and then about 7, 000g wet weight m-2 until 36 months on the blocks. The dominant species through the succession changed from Colpomenia sinuosa into Ecklonia cava as follows: Colpomenia sinuosa→Zonaria diesingiana→Sargassum spp.→Ecklonia cava. It took one and half years for this community on the artificial reefs to achieve the climax phase, which were well comparable to the neighboring area.