Researchers suggest global warming has had a more devastating effect on some of the world's finest coral reefs than previously assumed.

An international team of researchers found large sections of coral reefs and much of the marine life they support may be wiped out for good after it surveyed 21 sites and over 50,000 square meters of coral reefs in the inner islands of the Seychelles from 1994 to 2005.

The research team, led by the University of Newcastle, comprising researchers from Britain, Australia and the Seychelles, published its first report on Monday to show the long-term impact of sea temperature rise on coral and fish communities.

According to the research, the long-term impact of the 1998 event, when global warming caused Indian Ocean surface temperatures to increase to unprecedented and sustained levels, killed off more than 90 percent of the inner Seychelles corals.

The research showed the 1998 event's main long-term impacts are down to the damaged reefs being largely unable to reseed and recover and the collapse of the reefs removed food and shelter from predators for a large and diverse amount of marine life - in 2005 average coral cover in the area surveyed was just 7.5 percent.

"We have shown there has been very little recovery in the reef system of the inner Seychelles islands for seven years after the 1998 coral bleaching event," lead researcher Nick Graham of Newcastle University said.

"Reefs can sometimes recover after disturbances, but we have shown that after severe bleaching events, collapse in the physical structure of the reef results in profound impacts on other organisms in the ecosystem and greatly impedes the likelihood of recovery," he added.

According to the survey, four fish species are possibly already locally extinct, and six species are at critically low levels, although their decline probably started to happen soon after 1998.

The survey revealed species diversity of the fish community had decreased by 50 percent in the heavily impacted sites.

Smaller fish have reduced in number more quickly than larger species but their decreased availability has started to have a more lasting effect on the food chain, and this effect is likely to be amplified as time goes on, the researchers said.

Source: Xinhua