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.

The adaptability of three Arctic microalgae to different low temperatures

In order to study the adaptability of Arctic microalgae to different environmental temperatures,the growth curves and antioxidase system of three microalgae （Skeletonema marinoi.Chlorella sp.and Chlamydomonas sp.） that were separated from the Ny-（？）lesund,the high Arctic,at different low temperatures （0℃,4℃and 8℃） were determined.The result showed that the adaptability of the microalgae to temperatures depended on the species.The growth rate,SOD and CAT activities of Skeletonema marinoi were the highest at 4℃, but MDA content was the lowest.The growth rate and enzyme activity of Chlorella sp.were the highest at 8℃,while the lowest MDA content presented at 0℃.The growth of Chlamydomonas sp.at the different temperatures was not so significant,the lowest MDA content presented at 8℃.The change of antioxidase system also depended on species and temperatures.Three indexes of antioxidase system of Skeletonema marinoi between 0℃and 4℃showed extremely significant difference（p0.01）.SOD activity of Skeletonema marinoi and Chlorella sp.between 0℃and 8℃showed significant difference（p0.05）, and the other two indexes of them differed insignificantly.Antioxidase systems of Chlamydomonas sp.at the three temperatures differed insignificantly.In conclusion, the three microalgae had good adaptability to the three temperatures; their MDA content presented a low level,and had unique physiological mechanism to adapt to the environment with different low temperatures.