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Weeds Answer to Algae Scourge
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A local scientist said he believes he has found a possible solution to the growing problem of blue-green algae outbreaks that have hit the country's lakes.


Yu Dan, a professor of botany and zoology at the College of Life Sciences at Wuhan University, said growing more aquatic weeds could curb lake contamination.


Yu reached the conclusion after his research team succeeded in removing large swathes of algae from the Liangzi Lake, situated between the three industrial cities of Wuhan, Erzhou and Huangshi on the middle reaches of the Yangtze River, by growing aquatic weeds.


"Aquatic weeds and algae are the two primary kinds of lake-borne plants and fight each other when in the same environment," Yu said.


"A good growth of aquatic weeds can absorb more nutrients, such as nitrogen and phosphorus, depriving the algae and improving the quality of the lake water."


Blue-green algae grows easily in polluted water with a high concentration of nitrogen and phosphorous and a temperature of about 18 C, he said. An excess of blue-green algae removes oxygen from the water, killing fish and other aquatic life.


Liangzi Lake, the second largest lake in Hubei Province, has an area of 28,000 hectares. In the late 1980s, regularly fell victim to algae outbreaks as a result of unrestricted development of aquaculture and the emergence of a large number of industrial plants, which discharged wastewater into it.


Since then, the local government has closed polluting companies, dismantled 2,000 hectares of aquacultural grounds, improved the environment around the lake and introduced fishing bans to curb the lake's degradation.


In addition, scientists led by Professor Yu have grown 13,333 hectares of aquatic weeds in the Liangzi Lake since 1992. These now grow in 80 percent of the lake.


The efforts appear to have paid off. Local environmental protection organizations have said the water in the lake has attained the I-category and II-category levels, making it good enough to drink.


The practice of planting weeds has also been implemented in the Changtan Reservoir in Taizhou, east China's Zhejiang Province, which was crippled by an algae bloom from 1999 to 2001.


Yu introduced water weed seeds and propagating agents to the reservoir in 2002 and has since grown 666 hectares of aquatic weeds. The quality of water is now at the II-category level, authorities have said.


Yu said he hopes to use the weed-planting technique to reduce pollution in other major lakes but there are no concrete plans and he is quick to recognize the scale of the task ahead.


"It is very hard to restore a damaged lake's ecological environment in a short period of time, but this is not a mission impossible if concerted efforts can be made over dozens of years," Yu said.


The scientific team led by Yu has built a resource bank and database of more than 150,000 aquatic weed samples collected over the past 25 years.


"I believe the growing of aquatic weeds is a cost-efficient method to prevent the ecological degradation of lakes and there are no technical barriers in this regard," Yu said.


(Xinhua News Agency September 5, 2007)

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