Warm seas threat to coral and marine life

Published on Saturday 25 July 2009 19:28

WARM ocean temperatures predicted to persist until October in the Caribbean and Gulf of Mexico could mean the loss of huge swaths of corals, US scientists have warned.

The National Oceanic and Atmospheric Administration's Coral Reef Watch network said conditions may lead to coral disease and bleaching, when the stressed organisms expel colourful algae living in their tissues, leaving them white.

Coral bleaching lasting more than a week can kill the organisms, since they rely on the algae for sustenance, leading to the loss of reef habitat for numerous marine species.

Sea surface temperatures in parts of the Caribbean are already at levels typically not seen until late summer months when the water is hottest, said C Mark Eakin, coordinator of NOAA's Coral Reef Watch.

Bleaching can occur when sea temperatures rise just a few degrees above the average of the warmest summer months.

Eakin noted that sea temperatures in some parts of this region already were at the higher threshold, around 30C, and that some bleaching had already begun. Those temperatures are expected to hold until October. Scientists fear the bleaching could exceed what was seen in 2005 in the Caribbean, the worst coral bleaching event in the region's recorded history when up to 90 per cent of corals suffered bleaching, with more than half dying.

"Just like any climate forecast, local conditions and weather events can influence actual temperatures. However, we are quite concerned that high temperatures may threaten the health of coral reefs in the Caribbean this year," Eakin said.

NOAA also warned of potential high sea temperatures stressing corals near the central Pacific islands of Kiribati, and between the Northern Mariana Islands and Japan.

Scientists hope the early warnings of potential coral stress will lead governments to take protective steps, including establishing temporary restrictions on users of coral reefs such as divers, boaters and anglers.

Land-based pollution, such as sewage, beach erosion, coastal development and overfishing are also to blame, experts say.

About 25 per cent of all marine species need coral reefs to live and grow.