The basic environmental variables and adaptability of phytoplankton communities to low light and salinity were studied using incubation experiments in Kongsfjorden, a high Arctic fjord of Spitsbergen, in late summer 2006. Chlorophyll a concentrations were steady or decreased slightly in darkness after one day or one week incubation. Chlorophyll a concentrations showed an initial decline when exposed to natural light after one week incubation in darkness, and then increased significantly. In a salinity experiment, the maximal growth rate was observed at a dilution ratio of 10%, however, higher dilution ratios (≥40%) had an obvious negative effect on phytoplankton growth. We suggest that the phytoplankton communities in fjords in late summer are darkness adapted, and the inflow of glacial melt water is favorable for phytoplankton growth in the outer fjords where the influence of freshwater is limited.
CUI ShikaiHE JianfengHE PeiminZHANG FangLIN LingMA Yuxin
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(p<0.01).SOD activity of Skeletonema marinoi and Chlorella sp.between 0℃and 8℃showed significant difference(p<0.05), 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.
The 16S and 18S ribosomal ribonucleic acid genes of microbial organisms collected from the contrasting environments (temperature,salinity,silicate,phosphate and nitrate,p <0.05) of the inner and outer basins of Kongsfjorden (Spitsbergen,Arctic) were studied using polymerase chain reaction-denaturing gradient gel electrophoresis(DGGE) fingerprinting.Comparison of the microbial fingerprints and the physicochemical parameters revealed that molecular methodology exhibited a greater sensitivity.Sequences obtained from bacterial DGGE were affiliated with four main phylogenetic groups of bacteria:Proteobacteria(Alpha,Beta and Gamma),Bacteroidetes,Verrucomicrobia and Cyanobacteria.The relationships between the genotype distribution of these microbes and associated biotic/abiotic factors,revealed by canonical correspondence analysis,showed that Station 1 at 30 m (outer fjord) was grouped separately from the other sites.This difference could be a consequence of the thermocline and base of the euphotic layer at this depth where the Atlantic and Arctic-type waters overlapped.
