China Project Uses Mussels to Clean up Lakes, Bring Back Fish KUNMING, China – Lake Dianchi, known as the pearl of the Yunnan-Guizhou plateau, is among this country’s ten largest lakes, covering 306 square kilometers and serving as main water source for millions of people. The lake remains a popular tourist destination. But the once common sight of dozens of fishermen floating along the lake has disappeared, as lake waters grow murkier from industrial and domestic waste pollution and fish die off.  | | Each Chinese giant freshwater mussel, Anodonta woodiana, can filter up to 40 liters fo water per day. |
“I used to be a fisherman but the number of fish started declining,” said Dong Jian-You, in his 40s, who gave up fishing when catch became so scarce that his income suffered. Now he runs a small convenience and grocery shop in a village near the lake. “Maybe if the water were clearer the fishing would be better.” Improving lake ecology, saving endangered species and helping fishermen cope with the changing nature of the lakes is the goal of a Development Marketplace (DM) project funded in 2006. Aptly called “Musselling in on Pollution,” the project tests the reintroduction of native freshwater mussels, Anodonta woodiana, as a cheap and sustainable water filter. This type of mussel lives up to 15 years and can filter up to 40 liters of water per day, clearing water as it consumes organic matter and algae and deposits various solids onto the lake beds. As the water clears up, native water plants begin growing. These plants serve as home for many native invertebrates, which in turn support diverse fish communities. The six largest Yunnan plateau lakes were once home to plenty of mussels. However, they have almost or fully died at each lake as its waters became polluted.  | | A DM project is reintroducing the native mussels as a source of water filtration. Here team members are testing water quality and survival rate of specimen. |
The project is working in nine experimental sites at three of the lakes. It breeds mussels in a lab at the Kunming Institute of Zoology (KIZ) and tests their survival and water filtration rate in different habitat conditions in pens along the lake sides. In severe pollution, the mussels die but in milder pollution, they survive and clear the water to a rate where fish can also breed and live. “We hope to demonstrate the widespread utility of this novel technique, which could be replicated in many of the world’s polluted freshwaters, to remediate polluted waters important for biodiversity and household use,” said project team leader David Aldridge. KIZ built the first three experimental mussel breeding pens at Lake Dianchi last year. Today, 80 percent of the specimen still live and filter water at a high rate. Breeding pens at Lake Erhai are not as successful. Water clarity improved while the mussels lived, but they lasted less than 12 months. Aldridge attributes the cause to a nearby government fish farming experiment that released chemicals into the lake, causing severe pollution.  | | A project team member holds out a few young specimen of mussels that are being reintroduced into the six plateau lakes. |
Li Xiu Juan, resident of a village near Erhai, says the lake has changed a lot in the past 20 years. Now in her 30s, she remembers drinking water from the lake side as a little girl, something no local resident would do now. As China’s industries boom, environmental problems mount. Pollution in Yunnan’s plateau lakes has been named national priority and the national government is carrying out a US$300 million clean up project mainly focused on regulating industries that pollute. The DM project is also tackling behavior change, but at the community level. A comprehensive awareness campaign that uses meetings, discussions, pamphlets and playing cards that feature endangered species has been carried out. TV shows and print advertising urge people not to dump wastewater or fertilizer run-off into the lakes. The project even created a brochure describing how conservation aligns with Buddhism. ”I have been really enthused by the support of our project by local communities and management bureaus,” said Dr. Aldridge. “The decline in water quality and the loss of biodiversity is something many people have experienced within their lifetime, so they have a real passion for turning things around.” He added: “We are already seeing improvements to water quality within our experimental sites, and our propagation program is generating many baby mussels. With continued education and outreach, along with the scaling-up of our methodologies, I am hopeful that we can help restore lakes such as Dianchi into the pearls they once were.”
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