Zooplankton boom and ice amphipod bust below melting sea ice in the Amundsen Gulf, Arctic Canada |
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Authors: | Haakon Hop Christopher J Mundy Michel Gosselin Andrea L Rossnagel David G Barber |
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Institution: | (1) Norwegian Polar Institute, Fram Centre, 9296 Troms?, Norway;(2) Institut des Sciences de la Mer (ISMER), Universit? du Qu?bec ? Rimouski (UQAR), 310 all?e des Ursulines, Rimouski, QC, G5L 3A1,, Canada;(3) Centre for Earth Observation Science, Faculty of Environment, Earth and Resources, University of Manitoba, Winnipeg, MB, R3T 2N2,, Canada |
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Abstract: | Early summer in the Arctic with extensive ice melt and break-up represents a dramatic change for sympagic–pelagic fauna below
seasonal sea ice. As part of the International Polar Year-Circumpolar Flaw Lead system study (IPY-CFL), this investigation
quantified zooplankton in the meltwater layer below landfast ice and remaining ice fauna below melting ice during June (2008)
in Franklin Bay and Darnley Bay, Amundsen Gulf, Canada. The ice was in a state of advanced melt, with fully developed melt
ponds. Intense melting resulted in a 0.3- to 0.5-m-thick meltwater layer below the ice, with a strong halocline to the Arctic
water below. Zooplankton under the ice, in and below the meltwater layer, was sampled by SCUBA divers. Dense concentrations
(max. 1,400 ind. m−3) of Calanus glacialis were associated with the meltwater layer, with dominant copepodid stages CIV and CV and high abundance of nauplii. Less abundant
species included Pseudocalanus spp., Oithona similis and C. hyperboreus. The copepods were likely feeding on phytoplankton (0.5–2.3 mg Chl-a m−3) in the meltwater layer. Ice amphipods were present at low abundance (<10 ind. m−2) and wet biomass (<0.2 g m−2). Onisimus glacialis and Apherusa glacialis made up 64 and 51% of the total ice faunal abundance in Darnley Bay and Franklin Bay, respectively. During early summer,
the autochthonous ice fauna becomes gradually replaced by allochthonous zooplankton, with an abundance boom near the meltwater
layer. The ice amphipod bust occurs during late stages of melting and break-up, when their sympagic habitat is diminished
then lost. |
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