2024 Volume 80 Issue 17 Article ID: 24-17207
The objective of this study was to determine the characteristics of seaweed attachment on floating structures constructed with the drifted pumice at the depth of 0-2.5 m. Blast furnace cement, tap water, and drifted pumice were mixed in a weight ratio of 1:0.5:2.2 to produce the pumice blocks (10 cm height, 10 cm diameter). The field experiments were conducted in Nagashima-cho, Kagoshima Prefecture. The pumice blocks were placed on Nov 13, 2023. After 22, 38, 58, 71, and 85 days of installation, the pumice blocks were collected. Wet weight of seaweed adhering to the top, side, and bottom of the pumice blocks was measured. The amounts of seaweed attached to the pumice blocks placed on the sea surface were highest at a depth of 0 m after 58-85 days of immersion, with seaweed densities ranging from 1.66-2.15 g/cm2 on the top, and 0.19-0.29 g/cm2 on the sides, decreasing to 0.10-0.17 g/cm2 on the top, and 0.02-0.05 g/cm2 on the sides at a depth of 2.5 m. The illuminance was highest at 0 m depth, and decreased with the depth. It is suggested that the pumice blocks are placed at a depth of 0 m for most suitable seaweed attachment.
