Upper Arctic Ocean water masses harbor distinct communities of heterotrophic flagellates

[摘要] The ubiquity of heterotrophic flagellates (HFL) in marine waters has beenrecognized for several decades, but the phylogenetic diversity of these small(ca. 0.8–20 μm cell diameter), mostly phagotrophic protists in theupper pelagic zone of the ocean is underappreciated. Community composition ofmicrobes, including HFL, is the result of past and current environmentalselection, and different taxa may be indicative of food webs that cyclecarbon and energy very differently. While all oceanic water columns can bedensity stratified due to the temperature and salinity characteristics ofdifferent water masses, the Arctic Ocean is particularly well stratified,with nutrients often limiting in surface waters and most photosyntheticbiomass confined to a subsurface chlorophyll maximum layer, where light andnutrients are both available. This physically well-characterized systemprovided an opportunity to explore the community diversity of HFL fromdifferent water masses within the water column. We used high-throughput DNAsequencing techniques as a rapid means of surveying the diversity of HFLcommunities in the southern Beaufort Sea (Canada), targeting the surface, thesubsurface chlorophyll maximum layer (SCM) and just below the SCM. Inaddition to identifying major clades and their distribution, we explored themicro-diversity within the globally significant but uncultivated clade ofmarine stramenopiles (MAST-1) to examine the possibility of nichedifferentiation within the stratified water column. Our results stronglysuggested that HFL community composition was determined by water mass ratherthan geographical location across the Beaufort Sea. Future work should focuson the biogeochemical and ecological repercussions of different HFLcommunities in the face of climate-driven changes to the physical structureof the Arctic Ocean.

[学科分类] 地球化学与岩石