World's largest brown tide threatens east China shellfish

A massive algae bloom that was first detected on China's east coast in 2009 has been identified as the world's largest brown tide, researchers said Wednesday.

"The brown tide, similar to the one that has been spotted on the east U.S. coast since 1985, could bring the destruction of fisheries in east China," said Zhou Mingjiang, a professor with the Institute of Oceanology under the Chinese Academy of Sciences (IOCAS) who conducted the research.

Zhou discovered that the yellowish-brown algae are of the same species as those found in the east U.S. coast's brown tide.

"Thus, it is a more destructive brown tide, rather than the more common red tide," Zhou said.

The brown tide is the first to hit China, making it the third country to be hit by such tides after the U.S. and South Africa.

The brown tide, first spotted off the coast of east China's Hebei province in June 2009, has restrained the growth of cultivated scallops, oysters and mussels. The tide expanded between 2010 and 2011, reaching 3,350 square km in July 2010, and is believed to be growing even larger.

"The brown tide broke out again in late May this year and has reached the coast of Shandong province, located south of Hebei," said Yu Rencheng, Zhou's colleague. "This might mean that the brown tide is expanding."

Brown tides have the effect of causing shellfish to stop eating, which eventually leads to their deaths, Zhou said.

Brown tides have ravaged shellfish populations in other regions. Residents of Picnics Bay in the state of New York fished 500,000 tonnes of scallops in 1982. However, their harvests brought almost nothing after the east coast brown tide broke out in 1985.

A brown tide also broke out in South Africa in 1996, which caused the collapse of the scallop and oyster breeding industry in Saldanha Bay, located southwest of South Africa, in only a couple of years.

"The coastal waters of Hebei and Shandong represent a major aquaculture industry base in China. The brown tide has put the industry at the risk of collapse," said Yu.

The brown tide caused direct economic losses of 205 million yuan (32.2 million U.S. dollars) in Hebei in 2010, according to the State Oceanic Administration (SOA).

The brown tide might also harm natural fishery resources, as the area is a spawning ground for many species of fish, Zhou said.

Brown algae is fragile and very small, making it difficult to conduct scientific research on the organism, Zhou said.

"U.S. scientists have done research on it for nearly 30 years. They have learned much more about it, but still haven't found out the measures to tame it," Zhou said.

The causes of brown tides, their toxicity and how they cause shellfish to stop eating are still unknown, Zhou said.

Zhou said a state-level research program should be launched to control and prevent the effects of the tide.

"We should step up international cooperation and obtain references from our U.S. counterparts," he said.