Abstract
As part of the Canadian contribution to the International Polar Year (IPY), several major international research programs have focused on offshore arctic marine ecosystems. The general goal of these projects was to improve our understanding of how the response of arctic marine ecosystems to climate warming will alter food web structure and ecosystem services provided to Northerners. At least four key findings from these projects relating to arctic heterotrophic food web, pelagic-benthic coupling and biodiversity have emerged: (1) Contrary to a long-standing paradigm of dormant ecosystems during the long arctic winter, major food web components showed relatively high level of winter activity, well before the spring release of ice algae and subsequent phytoplankton bloom. Such phenological plasticity among key secondary producers like zooplankton may thus narrow the risks of extreme mismatch between primary production and secondary production in an increasingly variable arctic environment. (2) Tight pelagic-benthic coupling and consequent recycling of nutrients at the seafloor characterize specific regions of the Canadian Arctic, such as the North Water polynya and Lancaster Sound. The latter constitute hot spots of benthic ecosystem functioning compared to regions where zooplankton-mediated processes weaken the pelagic-benthic coupling. (3) In contrast with another widely shared assumption of lower biodiversity, arctic marine biodiversity is comparable to that reported off Atlantic and Pacific coasts of Canada, albeit threatened by the potential colonization of subarctic species. (4) The rapid decrease of summer sea-ice cover allows increasing numbers of killer whales to use the Canadian High Arctic as a hunting ground. The stronger presence of this species, bound to become a new apex predator of arctic seas, will likely affect populations of endemic arctic marine mammals such as the narwhal, bowhead, and beluga whales.
Highlights
From fisheries to the renewal of oxygen and from ecotourism to the sequestration of greenhouse gases, marine ecosystems and the biota they support provide humans with multiple services
We present a selection of preliminary research results and distil some of the main findings on arctic marine ecosystems acquired through three major International Polar Year (IPY) projects: the Circumpolar Flaw Lead System Study (CFL); Canada’s Three Oceans (C3O); and Global Warming and Arctic Marine Mammals (GWAMM)
Among the reasons responsible for this increasingly challenged view is the high seasonality of marine primary production that is strongly constrained to the short time window of a few weeks when snow melt and ice break-up allow for photosynthetically active radiation to reach the surface water column (Tremblay et al 2012)
Summary
From fisheries to the renewal of oxygen and from ecotourism to the sequestration of greenhouse gases, marine ecosystems and the biota they support provide humans with multiple services. The extreme climate that has prevailed over the Arctic Ocean for several million years has shaped unique marine ecosystems characterized by organisms that are adapted to frigid temperatures; the alternation between polar night and midnight sun; a perennial or seasonal sea ice cover, limiting nutrients in the stratified surface layer; and an extremely pulsed cycle of primary production (Fig. 1). Arctic cod inhabit the ice pack for part of their life cycle (Gradinger and Bluhm 2004) and form large overwintering aggregations at depth during the ice-covered season (Benoit et al 2008) Another ubiquitous consumer of copepods is the hyperiid amphipod Themisto libellula that funnels a significant fraction of the energy between the plankton and the higher trophic levels in ice covered seas (Dalpadado 2002; Welch et al 1992). We provide an up-todate status of knowledge on Arctic marine biodiversity, gained from the CHONe and Arctic Census of Marine Life initiatives
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