Natural remedy fights invading Qingdao algae

“The fish like eating algae, and plankton is among their favorites,” Chen Guobiao, a local fish farmer, told China Daily, after experimenting in a sea cucumber pond since May 2010.

Chen put 5,000 Siganus oramin, or nicknamed lanziyu in China, in his 2-hectare sea cucumber farm early in June, before the plankton had spread off the shore of Qingdao.

“As a result, hardly any plankton was seen in the farm in the following months and the fish did not harm the sea cucumbers,” he said.

One experiment Chen and his co-workers conducted showed that 20 lanziyu could consume five kilograms of algae in less than 20 minutes.

He said that in June to September in recent years, the plankton clogged the farms. The algae die after a time and the resulting decay consumes much of the oxygen in the water, harming the growth of aquacultural products.

Farmers had to dedicate enormous resources to removing the green algae.

“In 2009, my company paid tens of thousands of yuan for the cleanup,” Chen said.

Lanziyu inhabit the tropical and subtropical Indo-Pacific and eastern Mediterranean waters and feed on algae. So far, their use as a biological weapon against green algae — especially that from the swarms of plankton in some coastal areas of East China in recent years — has not been officially approved.

An algae bloom, reported to be 70 meters wide and 100 meters long, has blanketed the sea near Qingdao No. 1 Beach, dyeing a ship's cable green.

But it is nothing compared with the 410-square-kilometer green algae bloom in the Yellow Sea being blown south by the wind toward Qingdao, said Liu Fenglin, spokesman with the North China Sea Branch (NCSB) of the China State Oceanic Administration (SOA). It is expected to reach the beach in two days.

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