Composition of phytoplankton controlled not only the formation of the Food Chain, but also the efficiency of energy transfer. At the same time, phytoplankton influenced the distribution of nutrient and the sedimentation of organic particulate matter. So study of phytoplankton community structures plays an important role in understanding the ecological function of phytoplankton. Photosynthetic pigments needed by photosynthesis, are very good biomarkers. They can be used to research and characterize phytoplankton community structure. Norwegian and Greenland Seas which are influenced by the Arctic water with low temperature and salinity and Atlantic water with high temperature and salinity. Understanding of correlation between environmental factors and phytoplankton community structure, is important for understanding the community structure of the marine organisms and their ecological function.
During the 5^th Chinese Arctic Research Expedition in summer 2012, we analyze the photosynthetic pigments from Norwegian and Greenland Seas by HPLC. Contributions of different phytoplankton assemblages to Chlorophyll a were obtained by Chemical Taxonomy (CHEMTAX), and thus resulted in composition of the phytoplankton community structure at the surface and subsurface water (about 30 m depth).
The result showed that average concentration of Chlorophyll a at surface water was 23.59 ng/L, lower than that at upper water (30.38 ng/L). The contributions of phytoplankton to Chlorophyll a were nano- > micro- > pico-one. Prasinoxanthin, Fucoxanthin, Alloxanthoxyletin, Peridinin, Zeaxanthin, 19'-but-fucoxanthin, 19-hexanoyloxyfucoxanthin were observed in the waters. Their distributions were relative to environmental factors, including Nutrients, temperature and salinity. These photosynthetic pigments showed negative correlations with temperature and salinity. Whereas they showed positive relations with nutrients, including NO₂^-,NO₃^-,SiO₃^2- and PO₄^3-. The correlations of different phytoplankton and environmental factors were different. Diatoms had a very significant positive correlation with SiO₃^2-, but had no correlation with PO₄^3-, NO₂^- and NO₃^-; Haptophytes-N had significant positive correlations with PO₄^3-, NO₂^- and NO₃^-; Haptophytes-S also had a positive correlation with PO₄^3-, but had no correlation with NO₂^- and NO₃^-. The maximum values of these photosynthetic pigments, except for Zea and Fuco, existed in the subsurface of the section BB.
The distribution and concentration of photosynthetic pigments could explain the distribution and abundance of the phytoplankton to some extent. Not only because the pigments are complex and multiple, but also because there are inevitable errors in the testing and sampling, we cant determine the existence and abundance of the phytoplankton. So we use the CHEMTAX to obtain the contributions of different phytoplankton assemblages to Chlorophyll a, and thus resulted in composition of phytoplankton community structure. The composition of phytoplankton showed that Haptophytes-S(28%), Haptophytes-N(21%), Diatoms(18%), and Prasinophytes (12%) were main assemblages in the picoplankton; the main composition of nanophytoplankton were Haptophytes-S(53%), Haptophytes-N(20%), and Diatoms(12%); meanwhile, Diatoms (63%) dominated the microphytoplankton, followed by Dinoflagellates(17%). Haptophytes-S, Haptophytes-N and Diatoms were dominant species in the surface and subsurface of section BB and AT belonging to the Norwegian and Greenland Sea. If Fucoxanthins and Diatomss existence in picophytoplankton could explain the tendency of phytoplankton to micro and miniaturization, these still need to be more sufficient evidence.