In situ multi-excitation chlorophyll fluorometer for phytoplankton measurements: Technologies and applications beyond conventional fluorometers

In this paper, we present the technology and evaluate the performance of a newly developed in situ fluorometer, Multi-Exciter, which can measure the excitation spectra of chlorophyll fluorescence both automatically and continuously. The Multi-Exciter has nine wavelength excitation LEDs to measure the excitation spectra. The fluorometer measures the discrete excitation spectra of phytoplankton. Then, the phytoplankton species composition can be estimated by solving the optimization problem. The fluorometer has a good linearity that is less than 0.1μg-Chla/l, and reduces errors (<;1.0%FS) in turbid water caused by reflectance induced by the excitation lights. These performances show that the fluorometer enables accurate measurements of phytoplankton excitation spectra with a wide range suitable for use in the field. The classification performance of the device is also evaluated in a laboratory setting.