Located at the junction of Jiangsu Province and Zhejiang Province, Taihu Lake is one of the five largest freshwater lakes in China. As a major water source of the Huangpu River and the Suzhou River, Taihu Lake has always been the “heart” of Jiangsu, Zhejiang, and Shanghai.
Since the 1980s, with the economic development of southern Jiangsu, the water quality of Taihu Lake has been gradually polluted by the sewage from surrounding factories. In 2007, the pollution level of Taihu Lake reached its peak. Wastewater, containing a lot of nutrients such as nitrogen and phosphorus, made the lake water over-nutrient, which led to the proliferation of cyanobacteria. Those cyanobacteria dyed the water of Taihu Lake into green, and the large amount of cyanobacteria deposited in shallow water blocked the light from entering the water body, preventing the plants in the deep water from performing photosynthesis. Plants and animals in Taihu Lake gradually died, making the river smelly and further polluting the water. This outbreak has seriously affected the domestic water consumption of more than 2 million people in Wuxi.
In addition, it is difficult and costly to eliminate the algal toxins released by cyanobacteria by using ordinary water treatment processes. And once the toxins enter the human body, they would cause great damage to our liver, and would even lead to lung cancer. Cyanobacteria are a very viable species, as they absorb more nutrients and grow faster comparing with other aquatic plants. Therefore, they have a crowding effect on other species and can occupy the niche of other species. When cyanobacteria grow excessively, they consume a lot of oxygen in the water, eventually lead to the death of other animals and plants (including edible algae) due to the lack of oxygen.
At the same time, the algal toxins originally in the cyanobacteria will be released into the water body and pollute the water. If resident around the lake drink this water with high algal toxins level for a long time, they would probably suffer from headache, fever, diarrhea, nausea or vomiting. Moreover, drinking water containing algal toxin can cause acute gastroenteritis and even liver cancer.
Massive death of fish will also threaten the aquaculture industry, leading to a sudden increase in the unemployment rate and even social instability. Therefore, the management of cyanobacteria cannot be delayed.
As early as 2001, the state implemented the “Introduction to the Yangtze River” project, which was to transfer the Yangtze River to the Taihu Lake in order to increase the liquidity of the Taihu Lake, and promoting the self-purification capacity. Implementation of this project has indeed improved the water quality of Taihu Lake, but it did take huge amount of time, cost and effort from the government, which was the main shortcoming of this project. From this point of view, the use of biological approach to solve the problem of cyanobacteria might be an effective and efficient alternative solution.