"Behind all these is a typical El Nino phenomenon," Wang Zhanggui, a leading researcher with the National Marine Environmental Forecasting Center, said yesterday.

Because of its influence, unusually warmer weather will persist in China's southern sea areas throughout the winter, leaving the areas vulnerable to a bloom of poisonous algae, known as red tides, warned Wang.

Normally, red tides rarely occur in winter. Warm weather condition causes the explosive growth of algae caused by an excessive accumulation of nutrients in sea water.

The algae consume much of the water's oxygen and release poisonous substances, both of which kill sea organisms.

The center has been issuing warnings of unusual weather that might result from the El Nino phenomenon, since the beginning of this year. But local people seem to have not paid enough attention.

An unexpected red tide rendered a fatal blow to the shellfish industry of Lianjiang County in Fuzhou, the capital of East China's Fujian Province, in mid-November, with an estimated loss of around 3 million yuan (US$362,000).

Although an excessive increase in shellfish density is the principle cause of the red tide, it would not have happened if the weather were not warmer than usual, said Li, an official with the county's fisheries authority.

"Winter used to be a profitable season when the local shellfish industry could improve its prospects by increased shellfish density. But we really should have reduced the density this year for such unusually warm weather," said Li.

But for those in China's northern sea areas, the El Nino phenomenon might be good news to a certain extent.

"Since the weather is warmer than usual, there will be less ice on the seas. This will save people living on the sea, such as those on drilling rigs, the costly ice-breaking costs," said Wang.

The El Nino phenomenon is caused by abnormal temperature increases in tropical water off the west coast of South America, which lead to global weather and climate anomalies. It affects China every two to seven years.

Initially coming into being in mid-June, this first typical El Nino phenomenon of the new century enters its mature phase this month and is expected to last until the end of next June, according to Wang.

China began to forecast El Nino phenomenon in 1996 and successfully predicted one in 1997 and another this year.

Fortunately, the current El Nino will do less damage to the environment than that in 1997. "The present El Nino phenomenon is not as severe as the previous one," said Wang.

But because it is almost a general rule historically that North China will be subject to drought, while South China has heavy rainfall in the year following the occurrence of the El Nino phenomenon, it is useful to adopt some precautionary measures, said Wang.

(China Daily December 12, 2002)