Preliminary investigations on Arctic microalgae by jointapplication of fluorescent instruments

In vivo fluorescence has a wide application in analyzing microalgae, including assessing phytoplankton biomass, rates of primary production and physiological status. This study describes a preliminary investigation on the joint application of the three kinds of fluorescence analysis in the physiological study of microalgae. Flow cytometry and fluorescence spectrometry were used to obtain the in vivo static fluorescence information of pigments, and a Pulsed-Amplitude-Modulation chlorophyll fluorometer was used to detect the dynamic fluorescence of chlorophyll. The validity of the joint application was proved by analyzing two labora- tory cultured Arctic microalgae, Pseudo-nitzschia delicatissima （Bacillariophyceae） and Thalassiosira sp. The higher value of minimum fluorescence yield in dark-adapted state （Fo）, actual photochemical efficiency of PSll （ФPSII）, and electron transport rate （ETR） exhibited positive results in a higher cell abundance and chlorophyll a content of P. delicatissima; whereas higher fl-carotene content of Thalassiosira sp. played an important role in the protection of photosynthesis.