The role of tropical cyclones in stimulating cyanobacterial (Microcystis spp.) blooms in hypertrophic Lake Taihu, China

Abstract

Weather-related disturbances, such as wind-generated waves, major rainfall events and large temperature shifts associated with frontal passages, are important drivers of ecological processes in shallow lakes. The influence of Pacific tropical cyclones on cyanobacterial blooms in China's third largest lake, Taihu, was studied during the passage of two typhoons using a continuous monitoring as part of an on-lake high-frequency recording platform, coupled to satellite-based remote sensing data. Short-term (on the order of hours) nutrient pulsing resulting from the passage of typhoons played a key role in bloom initiation and maintenance. Decreasing wind speeds and increasing air and water temperatures in the aftermath of cyclones were accompanied by elevated phytoplankton biomass concentrations. The synergistic effects of nutrient pulsing, elevated water temperatures and increased water column stratification after the passage of the cyclones stimulated blooms of the toxic cyanobacteria Microcystis spp. There were short-term successions of blooms following typhoons, and as blooms “crashed” they provided nutrient inocula for future blooms. Trends determined from historical in situ data indicated higher frequencies and intensities of blooms in “cyclone years”. Typhoons are an important driver of biogeochemical and water quality perturbations at the ecosystem-level in this hypertrophic lake. These events play a key role in our ability to forecast blooms over both short (days) and longer-term (weeks) periods.