Zooplankton respiration and the export of carbon at depth in the Amundsen Gulf (Arctic Ocean)

Abstract

In arctic seas, lipids accumulated by zooplankton migrants in the surface layer in spring‐summer are respired at depth during the winter. The resulting active downward transport of carbon by the 200–1000 and >1000 μm mesozooplankton fractions was quantified based on 41 biomass and respiration profiles from October 2007 to July 2008 in the Amundsen Gulf (Canadian Arctic Ocean). The small fraction, dominated by CII‐CIII Calanus glacialis, represented on average 12% of the overall zooplankton biomass and contributed little to the active transport of carbon by respiration. From April to July, total zooplankton ingested 17–28% of the estimated gross primary production (GPP) in the surface 100 m, and 36–59% of GPP over the entire water column. The large fraction, comprised mainly of CIV, CV and adults Calanus hyperboreus and C. glacialis that accumulate large lipid reserves, was responsible for 89% of grazing. The downward migration of large zooplankton in late summer coincided with a sharp decline in specific respiration rates signaling the start of diapause and the endogenous fuelling of metabolism. From October to April, Calanus migration‐respiration actively transported 3.1 g C m−2 beyond 100 m, a flux that represented 85 to 132% of the gravitational POC fluxes at 100 m from October to July. Our results stress the importance of including active transport by large zooplankton migrants in carbon budgets of the Arctic Ocean.

Current state and trends in Canadian Arctic marine ecosystems: II. Heterotrophic food web, pelagic-benthic coupling, and biodiversity

“…These copepods typically comprise the bulk of biomass in the deep AL and PH of Amundsen Gulf in winter (Darnis et al 2008;Darnis and Fortier 2012). In general, we observed that the winter vertical distribution of arctic cod coincided with that of its zooplankton prey in the AL of Amundsen Gulf (Geoffroy et al 2011).…”

“…We would thus expect to find more opportunistic and active feeders in the small size fraction in winter. Over a quasi-annual cycle, the specific respiratory carbon loss of small zooplankton was variable as an indication of opportunistic foraging behaviour, and did not display the clear seasonal pattern observed in the large organisms (Darnis and Fortier 2012). Moreover, their diffuse distribution in the water column and their high specific respiration from the start of the CFL sampling in October until January suggested that they were actively feeding in autumn and early winter.…”

“…By resolving vertical distribution and respiratory carbon loss over a quasi-annual cycle, Darnis and Fortier (2012) assessed the relative importance of two zooplankton size classes in the pelagic food web.…”

Seasonal copepod lipid pump promotes carbon sequestration in the deep North Atlantic

“…Other zooplankton-mediated processes include the feeding and disruption of particle fluxes (8,9), and their active transport by vertical migrations (10,11). In particular, active transport to the deep ocean by annual ontogenic migrations of various copepod species (12)(13)(14)(15) has been shown to be potentially important in sequestering carbon in different locations. Less well documented is how carbon sequestration associated with these annual overwintering migrations compares to other processes at the scale of ocean basins.…”

From polar night to midnight sun: Diel vertical migration, metabolism and biogeochemical role of zooplankton in a high Arctic fjord (Kongsfjorden, Svalbard)

“…One study based on a 10‐month analysis of zooplankton in the southeastern Beaufort Sea revealed the importance of seasonal vertical migration (SVM) for carbon budgets in Arctic systems (Darnis and Fortier ). Carbon export below 200 m depth, mediated by large seasonal migrants such as the Arctic copepods Calanus hyperboreus and Calanus glacialis that overwinter at depth, was found to be of the same magnitude as the annual sinking POC flux measured by sediment traps.…”