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19,044,000 Yen (FY1996; 9,512,000 Yen)
I.Terrestrial area
This research aims at studying the influence of red soil outflow on coral reef. The object region of research is composed of three areas, namely Sesokojima area, Kuroshima area and Amitoriwan area. In investigation, we analyzed land use, average degree of inclination and the distance from river or seashore and studied the degree of danger of red soil outflow.
As a result, it was made clear that the area with the highest degree of danger of red soil outflow was Sesokojima area The area with the lowest degree of danger was Amitoriwan area. Intermediate degree of danger was shown in Kuroshima area among the above three areas. 32.1% of Sesokojima area was evaluated at "dangerous" land. Three were quarries, land under development, golf links, pineries, etc. in this "dangerous" land. There is scarcely any "dangerous" land in Kuroshima area and Amitoriwan area. 96.6% of Amitoriwan area was evaluated at "safe" and "comparatively safe". This value is about twice the value of Kuroshima area or Sesokojima area. "Safe" or "comparative safe" area is flat forest area or forest area, distant from river or seashore.
II. Marine area
To evaluate the effect of land development on coral communities we conducted monitoring of coral communities and recorded environmental conditions at 3 study sites in Okinawa Prefecture, Japan, in 1995 and 1996. We selected 5 stations each at (1)Sesoko Island, (2) Amitori Bay, and (3) Kuroshima Island. The land development is most progressed at (1), negligible at (2), and intermediate at (3). For environmental conditions, we analyzed sediment collected by traps, and water quality(salinity, SS, Total-N, NH4-N, NO2-N, NO3-N, Total-P). We found within-locality variation in the environmental parameters. However, we cannot detect clear trend in among-localities difference. We monitored coral communities in permanent plots, and recorded number of coral recruits onto artificial settlement plates. We detected significant decrease in coral percent cover only at (1). The decrease was mainly due to predation on tabular Acropora by Acanthaster planci at (1). In contrast, coral percent cover tended to increase at (2) and (3). Coral settlement was greater in 1996 than in 1995 at the 3 study sites. Coral settlement tended to be less at (3) than at (1) and (2).
Coral reef, Coral community, Coral settlement, Land Classification, Land Use, Mesh analysis, Red Soil, Sediment, Water quality