Quantitative retrieval of phytoplankton pigment based on water inherent optical properties in Lake Taihu
基于水体固有光学特性的太湖浮游植物色素的定量反演

Total 92 sampling waters were collected from different lake regions in Lake Taihu from May to August in 2005. Absorption coefficients of total particles and chromophoric dissolved organic matter (CDOM), beam attenuation coefficient, scattering coefficients, backscattering coefficients were measured and calculated. Spatial distributions of chlorophyll a, pheophytins concentrations, spectral features of total absorption coefficients and backscattering coefficients were also discussed. Chlorophyll a, pheophytins concentrations were in the range of 3.9 - 149.8 microg x L(-1) with a mean value of (38.14+/-28.89)microg x L(-1) ; 0 - 45.8 microg x(L-1) with a mean value of (8.49+/-7.24) microg x L(-1), respectively. A significant spatial difference was found for chlorophyll a, pheophytins concentrations with lower values in lake center, and typical macrophyte lake regions such as East Lake Taihu, Xukou Bay and Gonghu Bay. Similar significant spatial difference was found for total absorption coefficients and backscattering coefficients with lower values in typical macrophyte lake regions such as East Lake Taihu, Xukou Bay and Gonghu Bay. at(440) and bt(550) ranged from 0.86 to 23.25m(-1) with a mean value of (6.21+/-33.31)(m1)', from 0.05 to 2.25(m-)1 with a mean value of (0.72 +/-0.52)m(-1). Total absorption coefficients increased from 00 to 650nm with a peak near 680nm and increased from 720 to 750nm due to pure water absorption. Total backscattering coefficients generally decreased from 400 to 750nm An optimum band combination of reflectance R (706)/R (682) was selected to model chlorophyll a, pheophytins concentrations in Lake Taihu. Determination coefficients retrieving chlorophyll a concentrations, sum of chlorophyll a and pheophytins concentrations were 0.823, 0.864 5 based on reflectance ratio R (706) /R (682), respectively. Retrieval model of phytoplankton pigment can be used to all the lake including macrophyte lake regions with leaving-water reflectance affected by lake sediment and submerged plants.