Description: Samples of under ice water were collected at 4 stations not far from the White Sea Biological Station of the Zoological Institute RAS (Chupa Inlet, Kandalaksha Bay) in April 2002. For the first time it was shown that in winter numerous phototrophic and heterotrophic flagellates together with diatoms inhabited water column under sea ice. Abundance and biomass of these small algae was comparable with similar summer data. Biomass of algae in 2-40 m layer in early April 2002 exceeded 300 mg C/m**2, increasing up to 0.69-2.9 g C/m**3 just under ice. Sinking of the algae was insignificant, may be due to active grazing in the thin upper layer of the water column. High abundance of heterotrophic flagellates and dinoflagellates may indicate importance of the microbial food chain. From obtained data it may be concluded that the vegetation season, as well as the season of high activity of nano- and microheterotrophs starts in the White Sea far earlier, than it was supposed before.

Description: In April 2002 at four stations located in the vicinity of the White Sea Biological Station, Zoological Institute, Russian Academy of Sciences (Chupa Inlet, Kandalaksha Bay) ice samples were taken. It was shown that phototrophic and heterotrophic flagellates inhabit White Sea ice together with diatoms and dinoflagellates. In addition to three well-known communities, namely, assemblages of the lower ice surface, assemblages of pore channels, and interstitial communities, an infiltration assemblage and that of melt ice pools not described for the White Sea before were found in the White Sea ice. Biomass of ice algae varied from 130 to 1400 mg C/m**2. Maximum biomass was observed in the lower part of ice (from 2.5 to 36 g C/m**3 or 50-720 mg C within the lower 2-4 cm layer). It is shown that beginning of spring algal growth in the White Sea should be related not to the period of release of the sea from ice and subsequent water warming, but to the period of ice melting at the sea-ice interface and, correspondingly, to increase in its illumination. Sea-ice algae entering water from ice long before beginning of spring ''bloom'' of typical pelagic phytoplankton are grazed by planktonic heterotrophs directly under sea ice and serve at this period as a basis for the pelagic food chain.

Description: The purpose of the present study was to explore the composition and variation of the pico-, nano- and micro-plankton communities in Norwegian coastal waters and Skagerrak, and the co-occurrence of bacteria and viruses. Samples were collected along three cruise transects from Jaeren, Lista and Oksoy on the south coast of Norway and into the North Sea and Skagerrak. We also followed a drifting buoy for 55 h in Skagerrak in order to observe diel variations. Satellite ocean color images (SeaWiFS) of the chlorophyll a (chl a) distribution compared favorably to in situ measurements in open waters, while closer to the shore remote sensing chl a data was overestimated compared to the in situ data. Using light microscopy, we identified 49 micro- and 15 nanoplankton sized phototrophic forms as well as 40 micro- and 12 nanoplankton sized heterotrophic forms. The only picoeukaryote (0.2-2.0 µm) we identified was Resultor micron (Pedinophyceae). Along the transects a significant variation in the distribution and abundance of different plankton forms were observed, with Synechococcus spp and autotrophic picoeukaryotes as the most notable examples. There was no correlation between viruses and chl a, but between viruses and bacteria, and between viruses and some of the phytoplankton groups, especially the picoeukaryotes. Moreover, there was a negative correlation between nutrients and small viruses (Low Fluorescent Viruses) but a positive correlation between nutrients and large viruses (High Fluorescent Viruses). The abundance of autotrophic picoplankton, bacteria and viruses showed a diel variation in surface waters with higher values around noon and late at night and lower values in the evening. Synechococcus spp were found at 20 m depth 25-45 nautical miles from shore apparently forming a bloom that stretched out for more than 100 nautical miles from Skagerrak and up the south west coast of Norway. The different methods used for assessing abundance, distribution and diversity of microorganisms yielded complementary information about the plankton community. Flow cytometry enabled us to map the distribution of the smaller phytoplankton forms, bacteria and viruses in more detail than has been possible before but detection and quantification of specific forms (genus or species) still requires taxonomic skills, molecular analysis or both.