The health of coral in part of Okinawa Prefecture has been deteriorating, with the warming of world seas in 1998 causing bleaching, an environmentalist group said Saturday.
There are various causes for the decline in the proportion of seabed covered by coral but the impact of coral bleaching is thought to be a major cause, said Yasuaki Miyamoto of the Coral Network, an organizer of last year's survey on the health of coral.
The situation was particularly bad at a site proposed for a new military-civilian airport off Henoko district in Nago, northern Okinawa Prefecture, group members said.
The proportion of seabed covered by corals at the site was 4 percent at 3 meters below the surface of the sea, down from 61 percent in 1998, and 9 percent at 10 meters below the surface, down from 66 percent, they said.
The government has proposed building the offshore airport to take over the helicopter functions of the U.S. Marine Corps' Futenma Air Station in Ginowan, central Okinawa Island.
The proportion of coral on the seabed has also fallen considerably off Iriomote Island, Okinawa Prefecture—to one-third of the 1997 level, the group members said.
The health of corals has not deteriorated much in other parts of Okinawa, including Ishigaki Island, as well as around Miyake Island south of Tokyo.
More than 130 divers and researchers participated in the survey.