Studies On Characteristics Of Rayleigh Scatter Spectrum Of In Vivo Phytoplankton

Three dimensional fluorescence spectrum is used for monitoring phytoplankton classes and their abundance in previous study. Avoiding or eliminating Rayleigh scatter signals is often a key procedure for improving detection sensitivity in phytoplankton fluorescence analysis in the previous study. However, it is found that there are much useful information of cell contents and abundance in the scattering signals. As a result, Rayleigh scatter spectra of phytoplankton were studied in this paper. It was predicted that by combining both Rayleigh scatter spectra and three dimensional fluorescence spectra, more information could be provided for better identification of phytoplankton classes and assessment of their abundance. This paper aims to study the characteristics of both Rayleigh scatter spectra and three dimensional fluorescence spectra of phytoplankton in order to obtain better combined spectra for identification of phytoplankton. Eleven red-tide blooming algae and dominant phytoplankton species in the East China Sea, including Alexandrium tamarense, Isochrysis galbana 3012,Platymonas helgolanidica, Prorocentrum micans, Pseudo-nitzschia pungen (PS0201-01), Skeletonema costatuma, Nitzschia closterium, Chaetoceros curvisetus, Chaetoceros gracilis, Chaetoceros didymus and Gymnodinium sp, which belong to five divisions of phytoplankton, were chosen and cultivated in lab cultures under different temperatures and illumination intensities.The main research work is as follow:1 Three kinds of spectra were studied: the Rayleigh scatter spectrum, the combined spectrum and the restructured Rayleigh scatter spectrum. The combined spectrum refers to the Rayleigh scatter spectrum combined with the pigment characteristic spectrum char_Dv1, while the restructured Rayleigh scatter spectrum refers to the spectrum of 70% of principle components. The discriminant analysis results show that the restructured Rayleigh scatter spectrum has best discriminant ability, then it is the combined spectrum.2 The similarity of the above three kinds of spectra of living phytoplankton was studied. Two indicators including the average relative error and the average correlation coefficient were used to evaluate the similarity of the above three kinds of spectra. For the combined spectrum, Is, Pl, Sk and Cu have better similarity than the others, Ps has the worst. Similar results were obtained by the other two kinds of spectra. The results indicate that the similarity of the three kinds of spectra of the eleven phytoplankton species is good enough for analysis. In this paper, the combined spectra were chosen for qualitative and quantitative analysis.3 Qualitative and quantitative analysis. Firstly, for each phytoplankton, highest peak of Rayleigh spectra were found and the linearity between cell density and peak value was studied in the cultivating condition. Then, qualitative and quantitative analysis of 59 mixtures of phytoplankton was carried out using the non-negative least square method (NNLS). The recognition rate for all the sample was 90% in class, 76% in genus. At last, cell density for each phytoplankton was estimated by the linearity equation and the result of NNLS.4 Rayleigh spectra of lugol staining phytoplankton were primarily studied. Hierarchical clustering was processed to classify the Rayleigh scatter spectrum of each phytoplankton. Each species have one standard fluorescence spectrum. The measuring precision of the spectra was studied.In summary, according to our knowledge this paper takes the lead in studying the Rayleigh spectrum of in vivo phytoplankton combined with the pigment characteristic spectrum char_Dv1. Using the combined spectra and NNLS method, dinoflagellates and diatoms can be distinguished from each other in laboratory cultures, and their abundance was estimated.