Shallow lake limnology and control of eutrophication in Lake Taihu

Abstract

Unprecedented high intensity and large-scale restoration have been conducted in Lake Taihu since 2007 when the water crisis happened in Wuxi, and the cumulative investment of various governance measures has exceeded 100 billion RMB. As the long-term monitoring indicated, the nitrogen and phosphorus concentration in Lake Taihu decreased significantly and the water quality improved during the first few years. However, the water quality fluctuated and cyanobacteria bloom rebounded during the recent years. Studies implied that the external loading of nutrients did not decrease in Lake Taihu, which was largely related to the increase of urban water consumption, low sewage discharge standard and insufficient reduction of non-point source pollution. Meanwhile, the internal loading was aggravated by continuous cyanobacteria blooms. In addition, the impact of internal loading on lake eutrophication and cyanobacteria blooms was hence exacerbated in the case that the characteristics of shallow lakes as small water depth and strong disturbance are in favor of the efficiency of phosphorus cycling and uptake. The intensity and frequency of cyanobacteria blooms, of which the spatial and temporal distribution is determined by lake hydrodynamics, were aggravated by the combined effects of climate warming and nutrient enrichment, and changes in meteorological and hydrological conditions such as the decrease in wind speed over the lake catchment and the increase in the intensity and frequency of rainstorm events. In order to control the eutrophication of Lake Taihu, ensure the water environment security and maintain the sustainable development of society and economy, we should combine the lakes and basins as a whole, and should be conscious of importance to the combination of natural science and technology, the humanities and management.