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Abstract: During the R/V Xuelong Arctic cruise in summer 2008, we investigated bacterioplankton and picophytoplankton abundance, biomass, spatial distribution, and these variables'' relationship with environmental variables in the Western Canada Basin. The bacterioplankton and picophytoplankton abundances in the upper 200m of the water column were 0.17–8.38×105 cellsml−1 and 0.01–17.71×106 cellsL−1, respectively. The average integrated bacterioplankton and picophytoplankton biomasses in the upper 100m of the water column were 413.3 and 118.8mgCm−2, respectively. Microbial biomass was comparable with previous reports and distributed mainly in the upper 50m of the water column. The bacterioplankton and picophytoplankton biomasses decreased with increasing latitude. Compared with eastern transects, which were strongly influenced by an influx of Pacific water, the western transects had relatively low temperature, high salinity, high nutrients, and high biomass. No significant relationships were detected between assemblages and water temperature or salinity, expect for one between bacterioplankton and salinity in the latitudinal transects. However, a significant negative correlation between picophytoplankton and nutrients and a significant positive correlation between bacterioplankton and picophytoplankton were observed. We suggest that this was mainly caused by the relatively low picophytoplankton biomass, occurrence of heavy stratification (nutricline), and the subsurface chlorophyll maxima (SCM) in study area. Heavy melting of sea ice in summer increases the stratification, which obstructs nutrient supplementation from deep waters, and this might increase the role of microbial assemblages in the upper water column in the Arctic basin area. [Copyright &y& Elsevier]

Abstract: Pigment absorption property of two arctic microalgae species (Skeletonema marinoi and Chlorella sp.) cultured at three temperatures (0, 4 and 8°C) was analyzed. Carotenoids and chlorophyll (Chl) c were positive factors to the high cell activities and primary productivities of S. marinoi at 4°C and 0°C, respectively; whereas Chl a had a positive effect on Chlorella sp. at all three temperatures, and carotenoids had a relatively high effect at 0°C. The absorption locations of photopigments were analyzed in detail using both fourth derivative and Symlet-6 wavelet analysis. Both methods precisely detected pigments with a relative large content; the fourth derivative analysis specifically detected the existence of a Chl a peak at about 410nm and showed better differentiation of diatoxanthin, whereas the wavelet analysis distinctively indicated the existence of chlorophyllide a, β-carotene, and Chl c. The separation limit to pigment peaks of the fourth derivative spectra (4nm) was 1nm higher than that of the wavelet high-frequency spectra (3nm). The wavelet high-frequency spectra were more stable in detecting pigment locations and were more effective in discriminating microalgae. Small algebraic difference of 10−16 between the reconstructed absorption spectra obtained by the inverse wavelet transform and their corresponding original spectra also showed the validity of Symlet-6 wavelet in the detection of pigments. Another specific discovery of this research is the existence of a Chl a allomer in Chlorella sp., which was detected by both methods. [ABSTRACT FROM AUTHOR]

Abstract: Flow cytometry (FCM) is efficient in detecting both abundance and optical physiological parameters including cell size and cellular carbon content—side scatter (SSC), carotenoids—green and orange fluorescence (FL1 and FL2), and red fluorescence—chlorophylls (FL3) can be obtained by FCM. The utilization of these physiological parameters in indicating water masses in Prydz Bay was investigated for the first time. Picophytoplankton were very sensitive to hydrophysical changes and present distinct characteristics of water masses: Picophytoplankton in water closer to the Amery Ice Shelf were more affected by salinity than by temperature, while temperature became more important than salinity the nearer the picophytoplankton were to the deep sea. The picophytoplankton dealt with declines in light by increasing the size of cells, which increase the fixation of carbon. This can also be increased by high temperature and salinity. Pure water masses can increase the content of chlorophylls and cellular carbon. Generally, the distributions of all the five parameters at upper water depths were less affected by temperature and salinity than by water masses; and these parameters can be as indicators to Summer Surface Water (SSW), Winter Water (WW) and Continental Shelf Water (CSW). [Copyright &y& Elsevier]