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We examined the sub-ice algal community in the Chukchi Sea during June 1998 using a remotely operated vehicle (ROV). Ice algae were observed on the under-ice surface at all ten stations (from 70°29′N to 72°26′N; 162°00′W to 153°56′W) and varied in abundance and distribution from small aggregations limited to depressions in the ice to nets, curtains and strands of Melosira. There was no relationship between percent cover of sub-ice algae and physical factors at the kilometer scale, but at the scale of individual ice floes the percent cover of sub-ice algae was positively correlated with distance from the floe edge and negatively correlated with snow depth. A significant positive relationship between the concentration of sediment pigments and percent cover of sub-ice could indicate a coupling between ice algal and benthic systems. Pieces of ice algae that appeared to be Melosira were observed on the seafloor to a depth of over 100 m and cells or spores of obligate ice algal taxa were collected from sediments from 44-m to 1,000-m deep. The large biomass of sub-ice algae observed at many stations in the Chukchi Sea and the presence of ice algae on the seafloor indicates that the distribution and abundance of sub-ice algae needs to be understood if we are to evaluate the role of ice algae in the Arctic marine ecosystem. [ABSTRACT FROM AUTHOR]

Our study describes the species composition of microalgae, primarily diatoms, in two ice cores collected from the Chukchi Sea in early June 1998. At least 251 species were present in 2 cores collected 10 m apart in first-year ice. This is a greater number of algal species in ice from one locality than has been recorded from any other area of the Arctic. Microalgae were distributed throughout the 173-cm-long core, but abundance and species composition varied among different sections of the core, with maximum species richness (108 and 103 species in the 94- to 103- and 103- to 113-cm sections, respectively) occurring in the middle sections. More than 237 species were recorded from this core. Only the bottom 20 cm of the shorter (110 cm) core was analysed and it contained 135 algal species, still an extraordinarily high number of species. Marine species dominated both cores, but typical brackish and freshwater species were also present. None of these species, however, had more than 1% relative abundance. It should be noted, though, that there were several distinct, but unidentified, species of unknown origin. Characteristic ice algal species (e.g. Nitzschia frigida, Navicula pelagica, solitary Navicula spp., in addition to Cylindrotheca closterium) were the numerical dominants in most sections of the long core, but phytoplankton and benthic species were quite abundant in some sections. One section was dominated by a blue-green bacterium, presumably of the genus Anabaena. The species composition is consistent with several different mechanisms for algal incorporation into ice (i.e. seawater filtration ice, seeding from the sea floor, freshwater input). Over time, ice dynamics and sources of ice in the Chukchi Sea appear to result in high numbers of algal species in the ice. It is also likely that season of collection contributed to the high number of species observed. Determining the geographical area of origin for the different species is however difficult, due to the large-scale pattern of ice circulation. [ABSTRACT FROM AUTHOR]

Abstract: The diel vertical migration (DVM) of zooplankton and pelagic fish in the southern Arctic Ocean (82°N) and in Rijpfjorden (Svalbard, Nordaustlandet, 80°N) was investigated in autumn 2004, when there were distinct differences in light conditions between day and night. We collected data on zooplankton and fish distribution using plankton nets, trawls, and an echo sounder together with data on environmental parameters including sea-ice distribution, hydrography, and in situ fluorescence in the water column. In Rijpfjorden, the Arctic phytoplankton bloom had culminated several weeks prior to the present study and all three Calanus species had migrated down to depths for over wintering and did not show any changes in vertical distribution. However, in the Arctic Ocean pack ice at 82°N, Calanus hyperboreus, was found in high abundances (up to 65ind.m−3) actively feeding on the Arctic bloom in September. They performed a classic DVM, feeding in the upper 50m during the night and descending to depths below 50m during the day. In Rijpfjorden, distinct DVM patterns were observed among the amphipod Themisto libellula, adult and juvenile stages of the pteropod Limacina helicina, and polar cod. Polar cod in Rijpfjorden fed on Calanus spp. and on L. helicina. We conclude that animals display DVM in the Arctic during autumn if they need to feed in food-rich surface waters. [Copyright &y& Elsevier]