ENVIRONMENT / ANDAMAN SEA

El Nino effect blamed for deadly 'red tide'

APINYA WIPATAYOTIN

Satun _ A decrease in sea temperatures caused by the El Nino phenomenon is blamed for the deaths of huge numbers of fish off Tarutao island.

A number of fish were found dead on Sunday near the western part of the island in the Andaman Sea. The incident coincided with a change in the colour of the water to red.

"Water off the Son Bay, where most fish died, became very cold," said Tarutao Marine National Park chief Naruebet Chumtong.

The fish, which inhabit deep water, came to the surface to escape the cold. Those which could not adjust to the different environment died, he said.

Officials also spotted whales which came near to shore to escape cold water, he said.

El Nino, or ocean warming, normally refers to an increase in ocean water temperatures around the equator.

When that happens, it causes cold, nutrient-rich currents to flow toward the Andaman Sea, with temperatures plunging from 26C to below 20C, said Kasetsart University marine scientist Thorn Thamrongnawasawat.

The cold water, together with strong sunlight and still water, led to the "red tide" off Tarutao, he said.

A red tide is a sea condition in which phytoplankton grow in large numbers. The plankton, some of which are harmful, feed on nutrients in the water.

"I think marine fish died from eating poison phytoplankton," Mr Thon said.

However, the Tarutao Marine National Park yesterday said examinations of the dead fish showed no traces of toxic substances, and the park has allowed villagers to eat the fish.

The Meteorological Department has predicted that El Nino will fade away and be replaced by the La Nina phenomenon, or ocean cooling, within the next two months.

But El Nino is believed to have wider impacts on other marine animals.

Mr Thon said he was worried about the next "red tide", which he expected would occur in a river mouth in neighbouring Trang province, saying breaching coral has been detected in Satun and Trang.

"The pale colour is a sign that soft coral has been damaged. This has happened before, 10 years ago in the north of the Andaman Sea, including Surin Island," Mr Thorn said.

He said the condition was caused by a reduction in temperature to below 20C from the normal temperature of 26, due to cold currents flowing from the Pacific Ocean to the Andaman Sea.
Soft coral is an attraction for divers in the Andaman Sea.

Bangkok Post
Tuesday April 03, 2007