High-frequency optical measurements in shallow Lake Taihu, China: determining the relationships between hydrodynamic processes and inherent optical properties

In order to determine the effect of wind-induced waves (influenced by wind velocity and direction) on the dynamics of optical properties in shallow lakes, we determined the short-term variability of the inherent optical properties (IOPs) in Meiliang Bay, Lake Taihu, China, by examining high-frequency data collected between 8 and 21 September 2010 from meteorology and optical sensors. The absorption and beam attenuation coefficients under strong winds were significantly higher than those under weak and moderate winds (t test, P < 0.001). Significant correlations were found between absorption, scattering, beam attenuation, and wind speed, showing that the hydrodynamic process was an important factor that influenced the instantaneous IOPs of the water. However, the different wind directions have a different effect degree on the IOPs. Western wind is the most important driven wind direction of this site. In addition, significant correlations were found between b (p)(440), c (p+g)(440), b (p)(677), c (p+g)(677), b (p)(440), and turbidity under each wind direction (P < 0.001). Exponential and hyperbolic exponent models of the absorption and beam attenuation coefficients were fitted, and linear models between a (p+g)(677), c (p+g)(677), and turbidity were developed. Thus, in shallow lakes such as Lake Taihu, using real-time high-frequency monitoring of the turbidity to deduce the water IOPs could be an efficient and practical approach. Our study will be helpful in monitoring the IOPs and in improving the accuracy of bio-optical models to estimate water quality parameters in Lake Taihu.