[Characteristics of absorption spectra of phytoplankton]

Nine typical phytoplankton species were chosen and cultivated under two temperatures (20 and 15 degrees C) and two illumi- nations (7000 and 1100 lux), and their absorption spectra at different growth period were measured. Firstly, singular value decomposition was used on the matrix, which is composed of the autoscaled spectra data. The S1/msigma(i=1)Si was used to compare the similarities of spectra. Twenty-five representative spectra were obtained for the nine species of phytoplankton. Among them, there are one spectrum for each of Isochrysis galbana and Chaetoceros Debilis, two for each of Platymonas helgolanidica and Chaetoceros curvisetus, three for Gymnodinium sp., and four for each of Alexandrium tamarense, Prorocentrum dentatum, Skeletonema costatuma and Synechococcus sp. Then, feature extraction was processed to obtain the characteristic spectra, including seven incontinuous wavelengths that have great ability to differentiate species. They are 340. 5-420. 5 nm, 423. 5-431 nm, 440.5-525.5 nm, 760.5, 763.5, 769.5 and 856.5 nm. Consequently, they form characteristic spectra. The discriminant result is 80%.