A massive red tide has swamped the eastern coast of south China's Shenzhen since September 1 and plagued more than 15 square kilometers of water so far.

According to the Shenzhen Ocean and Fishery Observation Station, the extensive red tide is non-toxic and currently will do no harm to fish or the marine food industry.

The local government has notified nearby inshore shrimp ponds to strengthen their water oxygenation systems before dawn and stop draining ocean water.

People have been warned not to swim in the Dameisha sea area where the highest red tide density is found.

It is the second time that red tides have flooded into Shenzhen's eastern coastline within a month.

In the middle of August, severe red tides swept over several areas along the coast in succession but ebbed about a week later.

Shenzhen's coast has suffered from six red tides so far this year.

Professor Zhou Kai, from the observation station, said the frequent outbreaks are mostly rooted in the wash out of large amounts of untreated sewage.

Overfishing also has resulted in a sharp decrease of inshore fish and shrimp stocks that are able to feed on algae.

Shenzhen has established 31 coastal observation stations to keep a weather watch for red tide outbreaks.

And China has positioned 33 red tide supervision centers nationwide, with 13 along the South China Sea.

In late August, the Chinese Society of Oceanography set up the first national red tide research and prevention committee in China.

Also in the last month, the National Marine Environmental Monitoring Center completed a national red tide information management system. The center has recorded historical data about the sea-related problem since 1993.

(China Daily September 6, 2004)