Cyanobacterial Blooms in Lake Taihu and its Response to Climate Changes

摘要

The decomposition of cyanobacterial bloom often cause displeasing odor and deteriorate the water quality, even cause crisis to the water supply. To recognize the process and mechanisms of the bloom formation, the hypothesis of “four phases of cyanobacteria bloom development” was put forward. The water bloom forecasted was implemented from 2007 to 2010 for protect the water supply in Lake Taihu, China. The bloom trends were analyzed and the bloom phenology was found to be associated with climate changes resulting from global warming during the past 23 yr. To account for the effects of climate variables on phenological events of cyanobacterial blooms in Lake Taihu, we retrieved satellite images and obtained climate data in Lake Taihu area from 1987 to 2009, along with water quality data and bloom records. We found that the shift in cyanobacterial bloom phenology was mainly due to the climate changes, not elevated nutrients, in Lake Taihu during the past 23 yr. Cyanobacterial blooms came earlier and lasted longer with the increase of temperature, sunshine hours, and global radiation, and the decrease of wind speed and precipitation every year. And among these factors, sunshine hours and wind speed were primary contributors to the bloom onset over the past 23 yr. Sunshine hours, wind speed, and minimum temperatures were good predictors for and determined the annual bloom duration. Therefore, our work offers direct evidence that global warming alters the phenology of cyanobacterial blooms through climate changes in terms of sunshine hours, wind speed, and temperature during the past 23 yr.