[Characteristics of the diffuse attenuation coefficient and its impact on aquatic ecology environment]

According to the optical property data measured in Taihu Lake at October and November 2006, the characteristics of the diffuse attenuation coeffcient (Kd), the contribution of each factor effecting on Kd and the effect of Kd on the aquatic ecology environment were analyzed. The results indicate that, the diffuse attenuation coefficient Kd of Taihu Lake has two main trends in the whole visible wavelength range (400-700 nm). The first type is that, Kd decreases with the wavelengths by exponential style in the range of less than 571 nm wavelengths, and the second type is that, Kd is in the form of fluctuations in the range of larger than 571 nm wavelengths. In the range of 400-700 nm wavelength, the absorption coefficient of pigment particles is the first contributors of diffuse attenuation coefficient. Non-pigment particles absorption and scattering coefficients is the second contributor, and the rate of contribution of yellow substance is the smallest. The Kd of Taihu Lake determines the light factor of the Taihu water ecosystem. The "water window" shaped by the Kd provides the light base for different kinds of ecosystem and the appearance of Microcystic aentginosa which is the preponderant algae in the "algal blooms" phenomenon.