Carbon fluxes in the Canadian Arctic: patterns and drivers of bacterial abundance, production and respiration on the Beaufort Sea margin (original) (raw)
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Journal of Geophysical Research, 2008
1] The Canadian Arctic Shelf Exchange Study (CASES) included the overwintering deployment of a research platform in Franklin Bay (70°N, 126°W) and provided a unique seasonal record of bacterial dynamics in a coastal region of the Arctic Ocean. Our objectives were (1) to relate seasonal bacterial abundance (BA) and production (BP) to physico-chemical characteristics and (2) to quantify the annual bacterial carbon flux. BAwas estimated by epifluorescence microscopy and BP was estimated from 3 H-leucine and 3 H-thymidine assays. Mean BA values for the water column ranged from 1.0 (December) to 6.8 Â 10 5 cells mL À1 (July). Integral BP varied from 1 (February) to 80 mg C m À2 d À1 (July). During winter-spring, BP was uncorrelated with chlorophyll a (Chl a), but these variables were significantly correlated during summer-autumn (r s = 0.68, p < 0.001, N = 38), suggesting that BP was subject to bottom-up control by carbon supply. Integrated BP data showed three distinct periods: fall-winter, late winter-late spring, and summer. A baseline level of BB and BP was maintained throughout late winter-late spring despite the persistent cold and darkness, with irregular fluctuations that may be related to hydrodynamic events. During this period, BP rates were correlated with colored dissolved organic matter (CDOM) but not Chl a (r s BP.CDOMjChl a = 0.20, p < 0.05, N = 176). Annual BP was estimated as 6 g C m À2 a À1 , implying a total BP of 4.8 Â 10 10 g C a À1 for the Franklin Bay region. These results show that bacterial processes continue throughout all seasons and make a large contribution to the total biological carbon flux in this coastal arctic ecosystem.
Respiration and bacterial carbon dynamics in Arctic sea ice
Polar Biology, 2011
Bacterial carbon demand, an important component of ecosystem dynamics in polar waters and sea ice, is a function of both bacterial production (BP) and respiration (BR). BP has been found to be generally higher in sea ice than underlying waters, but rates of BR and bacterial growth efficiency (BGE) are poorly characterized in sea ice. Using melted ice core incubations, community respiration (CR), BP, and bacterial abundance (BA) were studied in sea ice and at the ice-water interface (IWI) in the Western Canadian Arctic during the spring and summer 2008. CR was converted to BR empirically. BP increased over the season and was on average 22 times higher in sea ice as compared with the IWI. Rates in ice samples were highly variable ranging from 0.2 to 18.3 lg C l-1 d-1. BR was also higher in ice and on average *10 times higher than BP but was less variable ranging from 2.39 to 22.5 lg C l-1 d-1. Given the high variability in BP and the relatively more stable rates of BR, BP was the main driver of estimated BGE (r 2 = 0.97, P \ 0.0001). We conclude that microbial respiration can consume a significant proportion of primary production in sea ice and may play an important role in biogenic CO 2 fluxes between the sea ice and atmosphere. Keywords Arctic Ocean Á Sea ice Á Respiration Á Bacterial production Á BGE Á C cycling This article belongs to the special issue ''Circumpolar Flaw Lead Study (CFL)'', coordinated by J. Deming and L
Changes in Arctic marine bacterial carbon metabolism in response to increasing temperature
Polar Biology, 2010
Arctic areas of deep-water convection have a large potential for export of organic carbon from surface waters into the deep sea and, therefore, are an important part of the global carbon cycle. As the Arctic is reportedly heating up faster than any other part of the planet, temperature-driven changes in the biogeochemical cycling in these areas can be very significant. Here, we study the regulation of bacterial carbon metabolism, which process vast amounts of organic carbon, by temperature and the availability of resources. The response of bacterial production and respiration of natural bacterial assemblages from the Fram Strait was studied by experimental manipulations of temperature and resources in combination. Both bacterial production and respiration were enhanced by temperature so that the total bacterial carbon demand increased sixfold following a temperature increase of 6°C. Respiration responded more strongly than production so that bacterial growth efficiency decreased with increasing temperature. Although neither production nor respiration was limited by resource availability under in situ conditions, the response to temperature was higher in resource-amended treatments, indicative of a substrate-temperature interaction regulating both components of bacterial metabolism. In conclusion, the results show that warming can result in a substantial increase of the carbon flow through bacteria and that most of the carbon consumed would be released as CO 2 . Moreover, the results suggest that both temperature and availability of resources need to be considered to accurately be able to predict changes in bacterial carbon metabolism in response to climate change.