Extensive and high-intensity pollution control and ecological restoration have been carried out in the entire Taihu basin since the drinking water crisis triggered by the cyanobacterial bloom in 2007. Some variables showed that from 2007 to 2017, water quality has been improved, but the cyanobacterial bloom hasn't been effectively contained. Total phosphorus concentrations have increased in recent years, and intense cyanobacterial blooms have persisted throughout 2017.

The contradiction between water quality and cyanobacteria bloom fluctuations and intensity management in Taihu Basin is confusing. The effectiveness of scientific and precise restoration of Lake Taihu has been widely questioned, and further the management of the lake and the formulation of ecological restoration programs have been hindered.

Recently, a research group led by Prof. QIN Boqiang from the Nanjing Institute of Geography and Limnology of the Chinese Academy of Sciences carried out multidisciplinary research, and proposed that regional extreme climatic anomalies could intensify nutrients cycling in the water-sediment interface and promote the cyanobacterial blooms in Lake Taihu. The study was published in Water Resources Research.

Multi-source data analysis showed that the abnormally high rainfall in the Taihu Basin in 2016 led to a sharp increase in external loading, and the winter temperature of 2016/2017 was the highest value since the 1960s, resulting in a high value of overwintering cyanobacteria biomass. It is the 2015/2016 super El Nino event and the warm phase of the Atlantic Multidecadal Oscillation (AMO) and Pacific Decadal Oscillation (PDO) that jointly induced heavy rainfall in the Taihu Basin in 2016 and the following warm winter.

After severe blooms in 2017, the pH of the water body increased and the concentration of dissolved oxygen at the bottom of the lake decreased due to photosynthesis or organic matter degradation, promoting the internal loading and benefiting the blooms. The enhanced nutrient cycle provides a continuous nutrient for the cyanobacterial bloom persistence.

This study demonstrated that under the big picture of global warming, regional extreme climate anomalies will further deteriorate lake water quality, and promote eutrophication and cyanobacterial blooms in eutrophic lakes.