Effects of typhoon Morakot on a large shallow lake ecosystem, Lake Taihu, China

Abstract

ABSTRACTA case study of typhoon‐induced sediment resuspension and its effects on some indicators of water quality (dissolved oxygen, pH and turbidity) and nutrient release in the large shallow eutrophic Lake Taihu, the third largest freshwater lake in China, was documented, and its effect on the algal biomass was investigated. Typhoon Morakot that swept from the west of Lake Taihu in August 2009 led to a number of changes in the lake ecosystem: (1) intensive winds produced large seiches, strong waves and large wave‐induced shear stress; (2) typhoon Morakot led to increased suspended solids and nutrients in the water column. Post‐typhoon concentrations of suspended solid, total phosphorus, total nitrogen, soluble reactive phosphorus (SRP). NO3‐N and NH4‐N were 4, 2, 1·5, 2·5, 3·5 and 1·5 times those observed in the pre‐typhoon water column, respectively; and (3) during typhoon Morakot, there was no obvious stratification between the surface and bottom of the water column in chlorophyll a (Chl a), the post‐typhoon Chl a concentration throughout the water column increased with a maximum daily mean of 87·8 µg l−1, and the algal bloom recurred. Typhoon‐induced sediment resuspension could lead to both nutrient and light limitations for algal growth, whereas after the typhoon had passed, water column conditions (water temperature, solar radiation, light penetration and nutrient availability) favoured the growth and production of algae. Copyright © 2011 John Wiley & Sons, Ltd.