In recent years, the research on climatic change and ecological system response finds that global or regional climatic change has promotion function to the occurrence of cyanobacteria blooms, and superimposes with lake water eutrophication, jointly promoting the increase of the intensity of cyanobacteria blooms. Researches mainly based on physiological property analysis of cyanophytes believe that temperature increment caused by global change is favorable to the growth of cyanophytes, while field observations often cannot fully support the viewpoint that temperature increment can promote the occurrence of cyanobacteria blooms. Therefore, it is necessary to deeply show that climate warming can cause the expansion of the intensity of cyanobacteria blooms to explain this phenomenon. Recently, the team of Kong Fanxiang, a research from Nanjing Institute of Geography & Limnology, Chinese Academy of Sciences, has obtained new progress in the research on the quantitative relation of intensity expansion of cyanobacteria blooms and climatic change.

The paper (Min Zhang et.al., 2012, 46: 442-452) of Zhang Min, a researcher of this team, published on Water Research believes that the increment of average temperature cannot effectively explain the intensity expansion of cyanobacteria blooms, which is mainly due to the complexity of temperature increment effects. Temperature is usually taken as an overall event in field researches, and direct effects of temperature are not separated from such indirect effects caused by temperature as stability increase of water and decrease of wind speed, while these factors will directly or indirectly affect the growth of alga and formation of blooms. This research uses remote sensing image data to obtain the phenology information of cyanobacteria in Taihu Lake of recent 20 years, selects main driving factors of intensity expansion (original time of occurrence and duration within the year of cyanobacteria blooms) of cyanobacteria blooms in Taihu Lake of recent 20 years, and carries out a quantitative study on contribution of different factors. The research finds that under the condition of high nutrient salt concentration of Taihu Lake, the intensity expansion of cyanobacteria blooms in recent 20 years are mainly affected by climatic change factors, in which wind speed and duration of sunshine are main factors of explaining the expansion of cyanobacteria blooms. These two factors explain the changes in the advance of original occurrence time of 84.6% cyanobacteria blooms and the expansion of duration within the year of 58.9% cyanobacteria blooms.

The global warming not only means the increment of average temperature, but also makes the temperature fluctuation in short time more severe and frequent. Due to small cell volume and short life cycle, floating alga are very sensitive to temperature fluctuations. This short-term temperature fluctuation will bring much uncertainty to researches on effects of climate warming on floating alga. Therefore, the evaluation of effects of global warming on formation of cyanobacteria species group advantage needs to consider the increment of average temperature, and also needs to consider effects of short-term temperature fluctuations. Zhang Min uses indoor simulation test and field observation data to find that rapid temperature fluctuations increase in spring is favorable to photosynthesis and growth of blue alga, while it is unfavorable to other alga. This result shows that during succession of alga species in spring, temperature fluctuations are likely to promote earlier establishment of population advantage of cyanobacteria. This research result has been published on Phycological Research (Min Zhang et.al., 2012, 60: 199-207).

This research fully recognizes the superimposed effects of water nutrient salt concentration and climatic changes to formation of cyanobacteria blooms, and believes that controlling cyanobacteria blooms under the condition of climatic changes needs higher requirements to reduction of water nutrient salt concentration. The research result has important directive significance to lake improvement and management decisions. The research above is sponsored by national “973” program, National Natural Science Foundation Program, and Jiangsu Natural Science Foundation Program.

（Information Source: Nanjing Institute of Geography and Limnology, CAS）