Abstract
Oceanic gateways are sensitive to climate driven processes. By connecting oceans, they have a global influence on marine biological production and biogeochemical cycles. The furthest north of these gateways is Nares Strait at the top of the North Water between Greenland and Ellesmere Island (Canada). This gateway is globally beneficial, first by supporting high local mammal and bird populations and second with the outflow of phosphate-rich Arctic waters fueling the North Atlantic spring bloom. Both sides of the North Water are hydrologically distinct with counter currents that make this Arctic portal a Janus gateway, after Janus, the Roman god of duality. We examined oceanographic properties and differences in phytoplankton and other protist communities from the eastern and western sides of the North Water (latitude 76.5°N) and found that species differed markedly due to salinity stratification regimes and local hydrography. Typical Arctic communities were associated with south flowing currents along the Canadian side, while potentially noxious Pseudo-nitzschia spp. were dominant on the Greenland side and associated with greater surface freshening from ice melt. This susceptibility of the Greenland side to Pseudo-nitzschia spp. blooms suggest that monitoring species responses to climate mediated changes is needed.
Highlights
Cold phosphate rich water from the Central Arctic and Lincoln Sea, along with first year and multi-year sea-ice into the North Atlantic[17]
On the Canadian side, there was a slight increase in salinity between the surface and the weak subsurface chlorophyll maximum (SCM) (31.45 to 32.35)
Within the Polar Mixed Layer (PML) the microbial eukaryotic communities from the two sides of the North Water differed taxonomically, with Pseudo-nitzschia dominated communities persistently found on the Greenland side, and more mixed communities on the Canadian side
Summary
Cold phosphate rich water from the Central Arctic and Lincoln Sea, along with first year and multi-year sea-ice into the North Atlantic[17]. An earlier microscopy study based on samples collected from a four-month series of transects from April to July 1998 in the North Water, found that microbial eukaryotic communities in both the surface and the upper waters that make up the Polar Mixed Layer (PML), differed regionally[22]. Previous expeditions to the North Water have sampled stations at more or less random times over the 24-hour cycle due to logistic constraints on multidisciplinary missions[25]. For these reasons, we repeatedly sampled the bottom of the PML in two one–day Lagrangian drifts, with one each of the Canadian and Greenland sides of the North Water (Fig. 1A, Supplementary Table S1). Given that microbial eukaryotes are sensitive indicators of water masses[26], the aim was to capture short term temporal and spatial variability in biological, chemical and physical parameters and link these to species composition and community changes
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