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To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.dsr.2009.10.002 Byline: Alexandre Forest (a), Simon Belanger (b), Makoto Sampei (a), Hiroshi Sasaki (c), Catherine Lalande (a), Louis Fortier (a) Keywords: Particulate organic carbon fluxes; Sequential sediment traps; Remote sensing; Environmental forcing; Inter-annual variability; Arctic Ocean Abstract: Surface concentrations and vertical fluxes of particulate organic carbon (POC) were assessed in the Amundsen Gulf (southeastern Beaufort Sea, Arctic Ocean) over the years 2004 to 2006 by using ocean color remote-sensing imagery and sequential sediment traps moored over the ca. 400m isobath. Environmental conditions (sea ice, wind) and oceanographic variables (temperature, salinity, fluorescence and currents) were investigated to explain the variability of POC data. Annual downward POC fluxes in 2004, 2005 and 2006 cumulated, respectively, to 3.3, 4.2 and 6.0gCm.sup.-2 yr.sup.-1 at [approximately equal to]100m depth, and to 1.3, 2.2 and 3.3gCm.sup.-2 yr.sup.-1 at [approximately equal to]210m depth. The fraction of settling POC attributable to autochthonous processes occurring at or next to ice break-up was estimated to be 75-84% of the 100m annual fluxes and to be 61-75% of the 210m fluxes. Over the three ice-reduced seasons, distinct scenarios between ice conditions, surface POC pools and vertical POC export at 100m were identified: (1) in 2004, despite a normal ice break-up, a weak primary production was measured and low vertical fluxes were collected as old ice moved across the region; (2) in 2005, a lengthened ice-free period allowed an extended season of surface POC production near-shore, while an intermediate increase of vertical fluxes was recorded offshore; and (3) in 2006, a late ice melt gave rise to a pulsed ice edge bloom and to large vertical fluxes also associated with extra ice-flushed material. Linear regressions of vertical POC fluxes against satellite-derived surface POC concentrations suggested that the pelagic POC retention in the upper 100m of the Amundsen Gulf ranged from ca. 70% to 90% depending on the timing of ice cover melt. Regardless of the inter-annual variability, the estimated fraction of the surface POC reservoir reaching the 210m water depth was reduced to [approximately equal to]5%. Therefore, as the Arctic Ocean warms up, our results support the expectation that the increasing extent of the seasonal ice zone will promote the POC pathways that benefit pelagic webs rather than benthic communities. Author Affiliation: (a) Quebec-Ocean, Departement de Biologie, Universite Laval, Quebec, Canada G1V 0A6 (b) Departement de Biologie, Chimie et Geographie, Universite du Quebec a Rimouski, 300 allee des Ursulines, Rimouski, Canada G5L 3A1 (c) Senshu University of Ishinomaki, Ishinomaki, Miyagi 986-8580, Japan Article History: Received 21 January 2009; Revised 22 September 2009; Accepted 2 October 2009

Typically, all undecomposed metazoans found in formalin-poisoned cups of sediment traps are considered to be active intruders (or 'swimmers') and are removed to prevent an overestimation of the downward particle flux. However, intact metazoans dead before entering the trap should be included in the estimation of downward flux of carbon. Arctic copepods collected in the field were killed either by formalin to mimic death by actively swimming into the formalin-poisoned cups, or by crowding or high temperature and then preserved in formalin to simulate death before entering the trap. In the crowding and heat treatments, 64% of Calanus hyperboreus and C. glacialis and 44% of Pareuchaeta glacialis differed from copepods killed by formalin in the postmortem posture of the antennules or swimming legs. These frequencies were used to estimate the contribution of passively sinking copepods (PSCs) to the particulate organic carbon (POC) flux measured by a sediment trap moored at 70 m in the Beaufort Sea (Canadian sector of the Arctic Ocean). PSCs represented only a small fraction (