2010 Volume 22 Issue 4 Pages 106-114
ABSTRACT: The Japanese coastal zones are affected by the warm current and the cold current. The various kinds of seaweed beds are distributed in Japan. In late years, the seaweed beds are decreasing nationwide. The seaweed beds are so-called "a cradle of the sea" bringing up the juvenile fish of many fishery resources. The functions of seaweed beds are the habitation area, the hiding area and the feeding area of the juvenile fishes. Furthermore, the seaweed beds have the function to absorb nutrient and carbon dioxide. Seaweeds become "the drifting algae", flow out into the offshore and change into inorganic matter. In this paper, firstly the process of the drifting algae have analyzed by numerical model. Secondly, several artificial seaweed reefs were compared the quantity of nitrogen absorption of the seaweed beds. Finally, the cost-effectiveness analysis of the seaweed bed creation in Bisan-Seto, Seto Inland Sea has carried out. Main results are as follows. The nitrogen absorption of seaweed beds is 0.18-0.57kg/year/m2, and its economical benefit is about 4,000-14,000 yen/year/m2. The drifting algae have the function to flow out nutrient into the offshore.
