During the period of spring bloom from March 3 to April 16,2005 in Xiangxi Bay, The vertical attenuation coefficients (K-Sd) of downward visible irradiance( PAR) and Secchi disc transparency (Sd) were measured with a scanning spectroradiometer and a 30 cm diameter black and white quadrant disc Water chemistry variables such as chlorophyll-a and dissolved organic car])on (DOC) were measured to determine the relative contribution of attenuating constituent in explaining the substantial variation in the PAR attenuation coefficients K-Sd. Based on the in situ, investigation data obtained, The underwater light field in Xiangxi Bay was characterised an(] the relationship between these two optical properties of the underwater was quantified with SPSS software. The analyses including application of empirical theories demonstrate that temporal patterns and inter-system differences in K-Sd and 1/Sd during the period were well correlated for most of the sampling sites,except in the Xiakou reach,and the inverse relationship these two optical properties is influenced by chlorophyll-a and inorganic tripton to some extent. Regression Analyses of these PAR attenuation coefficient data and observations of Chla and DOC, documente that Chlorophyll a and Dissolved organic carbon are the important constituents responsible for spatial distribution and temporal variation of the PAR attenuation coefficients K-Sd in Xiangxi Bay, except in the Xiakou raech. In addition to application of empirical and deterministic modeling frameworks, those results demonstrate that the Xiangxi Bay in the optic characteristic during the period of spring bloom is similar to many deep lakes, and differ from many shallow lakes where increase of total suspended matter due to sediment resuspension results in decrease of transparency and increase of beam attenuation coefficient.
Xu Yao-Yang; Ye Lin; Han Xin-Qin; Cai Qing-Hua (email@example.com).Characteristic and regression analysis of the PAR attenuation coefficient in Xiangxi Bay during spring bloom,Acta Hydrobiologica Sinica,2006,30(1):84-88