Because of the limitations of sampling and seasonal study in polar regions, knowledge of dinoflagellate diversity, distribution and ecology are limited. Dinoflagellates have been incidentally reported from polar regions during some seasons and some populations have been reported as components of microalgae. Surveys of molecular diversity link the genotype of dinoflagellates from polar regions with environmental adaptation. In this study, 37 positive clones of dinoflagellates collected from different sites were used for genotype analysis, providing new insights into the biodiversity and distribution of these species based on 18S rRNA sequencing. Diverse genotypes were recorded for the summer season in Kongsfjorden （high Arctic） whilst a single novel genotype of dinoflagellate was recorded from winter samples from the Antarctic Ocean. Data from ice cores suggests that this single dinoflagellate genotype was adapted to extreme cold and clone library screening found that it was occasionally the only microbial eukaryotic genotype found in winter ice cores. The findings of this study could improve our understanding of the diverse dinoflagellate genotypes occurring in these perennially cold microbial ecosystems.
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.
