A new research has suggested that rising ocean temperatures may leave corals and rainforests without clouds for protection.

Five years ago, Graham Jones and his team at Southern Cross University in Lismore, New South Wales, Australia, demonstrated that algae living in coral tissue produce a gas called dimethyl sulphide (DMS). When released into the atmosphere, DMS helps clouds form over coral reefs. Jones says that the clouds block sunlight and cool the sea.

His team has now discovered that a rise in ocean temperature of only 2 degree Celsius causes some algae to stop producing DMS. As a result, fewer clouds will form over the coral, allowing more sunlight to shine on the water, warming it still more.

“When the water temperature rose from the annual mean of 24 degree Celsius to 26 degree C, no DMS was released,” said Jones.

The gas is oxidised and forms small sulphur aerosol particles that attract water vapour and produce clouds.

The findings support Jones’s past work, which found that extreme warming of water around the Great Barrier Reef in the early 1990s led to lower DMS levels in the water. But, he said that this is the first study to measure the effect of water temperature on the amount of DMS entering the atmosphere.

Jones also suspects that DMS may have a significant role in the regional climate of north Queensland. He said that in winter, south-easterly trade winds may carry the DMS aerosol particles into rainforests, producing rain; in the monsoon period, north-easterly winds are responsible for the rainfall.

“We believe it is no coincidence that much of Australia’s rainforest lies adjacent to the northernmost reefs,” said Jones. If this is true, lower levels of DMS over coral reefs could dry out north Queensland’s rainforests, according to Jones.

According to David Bourne (PDF) of Australia’s Institute of Marine Sciences in Townsville, Queensland, it’s likely that rising ocean temperatures could stop the production of DMS. At high temperatures coral expel their algae. “If you lose the algae, it makes sense that you see the loss of DMS,” said Bourne.