A fluorometric differentiation technique of phytoplankton assemblage based on Coif2 wavelet and fourth-derivative

The: 3D discrete fluorescence spectra with 12 excitation wavelengths (400, 430, 450, 460, 470, 490, 500, 510, 525, 550 , 570 , 590nm) were determined by fluorescence spectrophotometer for 20 phytoplankton species. Then, the wavelet (Coif2), fourth-derivative and non-negative least squares were applied to establish the fluorescence differentiation method which could differentiate phytoplankton populations at the levels of both division and genus. This method was tested: for simulative mixed samples (the dominant division algae accounted for 50%, 70%, 90% and 100% of the gross biomass, respectively) at the level of division, the discrimination rates were 94.4%, 97.8% 98.6% and 98.4%with average relative content of 48.2%, 65.1%, 79.4% and 77.9%, respectively. For simulative mixed samples(the dominant species accounted for 70%, 80%, 90% and 100% of the gross biomass, respectively) at the level of genus, the correct discrimination rates were 72.7%, 82.2%, 86.5% and 81.0% respectively. For the in situ test, all of the 12 samples were recognized at the division level, and for the three samples which the dominant species accounted for more than 80% of the gross biomass, the dominant species of one was recognized at the genus level. As a result, an in situ algae fluorescence auto-analyzer which uses a series of LEDs as the light sources is developing. The technique also can be directly applied on fluorescence spectrophotometer.