What is coral bleaching?

One of the most visually dramatic effects of climate change on corals, has been bleaching. When the ocean warms, the oxygen content reduces, and corals become ‘bleached’.

The heat affects the tiny algae which live symbiotically inside the corals and supply them with food. The heat stress damages the algae and in consequence leads to coral death.

Global warming could now mean a death sentence for many coral reefs. If the present rate of destruction continues, most of the world’s coral reefs could be killed within our lifetime.

Coral reefs are extremely important for biodiversity, providing home to over 25% of all the marine life. They provide nurseries for many species of commercially important fish, protection of coastal areas from storm, waves, and are a significant attraction for the tourism industry.

Coral reefs around the world have been severely damaged by unusually warm ocean temperatures.

However, coral reefs are very fragile sensitive ecosystems that can only tolerate a narrow temperature range.

JAKARTA, Aug. 20 (UPI) — A dramatic rise in the surface temperature of Indonesian waters has devastated local coral populations, research shows.

Marine biologists with the Wildlife Conservation Society, in an initial survey of the waters in May, found that more than 60 percent of the coral had “bleached,” which occurs when algae living within coral tissues are expelled.

By August, surveys by researchers from Australia’s James Cook University and Indonesia’s Syiah Kuala University showed 80 percent of those bleached corals had since died.

“It’s a disappointing development, particularly in light of the fact that these same corals proved resilient to other disruptions to this ecosystem, including the Indian Ocean Tsunami of 2004,” said Stuart Campbell, marine program director for the Wildlife Conservation Society of Indonesia.

Sea surface temperatures in the Andaman Sea — an area that includes the coasts of Myanmar, Thailand, the Andaman and Nicobar Islands, and north western Indonesia — have been on the rise.

According to the National Oceanic and Atmospheric Administration’s Coral Hotspots Web site, air temperatures in the region peaked at 93 degrees Fahrenheit in late May, representing a 7 degree rise over long-term averages for the area.

The coral bleaching is caused by a combination of warmer water and greater exposure to sunlight that is unfiltered by clouds or wind.

The August findings represent “a tragedy not only for some of the world’s most biodiverse coral reefs, but also for people in the region, many of whom are extremely impoverished and depend on these reefs for their food and livelihoods,” Caleb McClennen, marine program director for the society, said in a statement.

“It is another unfortunate reminder that international efforts to curb the causes and effects of climate change must be made if these sensitive ecosystems and the vulnerable human communities around the world that depend on them are to adapt and endure,” he said.

Clive Wilkinson, a coordinator at the Global Coral Reef Monitoring Network in Australia, told the Voice of America the bleaching appears to be spreading to Vietnam and Southeast Asia. He warned that it could reach Taiwan and southern Japan very soon.

“We’re sadly quite convinced that this is a climate change event,” Wilkinson said. “What’s happened is that there is far more energy in the atmosphere and in the oceans at the moment because of global warming.”

While coral reefs account for just 1 percent of the world’s ocean surface, they provide a home for 25 percent of all sea life.