サンゴ礁沿岸での海域ゾーニングの試み

抄録

Numerical simulation was conducted for coral reef conservation in port area from the hydraulic point of view. Naha Port in south western part of Japan was selected as an example. Coral reef is said sensitive to turbidity of fine silt, water salinity and temperature, activity of predators and so on. For the maintenance of the ecological activity and the reef-zoning, larvae support from mother reef is important. Coastal hydraulics mainly affect a).diffusion and settling of the turbidity load from the land area, and b).drifting route of the released eggs/larvae from mother coral reefs.
Calculations on coastal flow, water exchange, drifting path of larvae and diffusion of turbidity were tried by numerical simulation models. For the calculation of drifting, larva markers are released from the main active reef area and drifting paths traced. For the calculation of turbidity diffusion, particle load and diameter fractions were estimated, using the observation data during a strong rain fall.
The critical values of turbidity nor settling rate are not yet established officially for coastal reef conservation. Comparing a damaged reef of another island, river mouth area in this port is relatively not suitable for coral transplantation. Outside fringes of the existing reefs, protected by breakwater from the inflow turbidity load, are expected to have the high potential as mother coral to north and south neighbor reefs. These results give useful information for the comprehensive planning of coastal water surface zoning at coral sea.