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MEPS 539:1-17 (2015)  -  DOI:

Seasonal carbon cycling in a Greenlandic fjord: an integrated pelagic and benthic study

Heidi L. Sørensen1,2,*, Lorenz Meire2,3,4, Thomas Juul-Pedersen2, Henko C. de Stigter5, Filip J. R. Meysman3,6, Søren Rysgaard2,7,8,9, Bo Thamdrup1, Ronnie N. Glud1,2,9,10

1Nordic Centre for Earth Evolution (NordCEE), Dept of Biology, University of Southern Denmark (SDU), 5230 Odense, Denmark
2Greenland Climate Research Centre (GCRC), Greenland Institute of Natural Resources, 3900 Nuuk, Greenland
3Royal Netherlands Institute of Sea Research (NIOZ), Department of Ecosystem Studies, 4401 NT, Yerseke, The Netherlands
4University of Ghent (UGent), Marine Biology Laboratory, 9000 Gent, Belgium
5Royal Netherlands Institute of Sea Research (NIOZ), Dept of Geology and Chemical Oceanography, 1790 AB Den Burg - Texel, The Netherlands
6Dept of Analytical, Environmental and Geochemistry (AMGC), Vrije University of Brussels (VUB), 1050 Brussels, Belgium
7Centre for Earth Observation Science, Dept of Environment and Geography, University of Manitoba, Winnipeg, MB R3T 2N2, Canada
8Dept of Geological Sciences, University of Manitoba, Winnipeg, MB R3T 2N2, Canada
9Arctic Research Centre, Aarhus University, 8000 Aarhus, Denmark
10Scottish Association for Marine Science, Scottish Marine Institute, Oban PA37 1QA, UK
*Corresponding author:

ABSTRACT: Climate change is expected to have a pronounced effect on biogeochemical cycling in Arctic fjords, but current insight on the biogeochemical functioning of these systems is limited. Here, we present seasonal data on primary production, export of particulate organic carbon (POC), and the coupling to benthic biogeochemistry in Kobbefjord (SW Greenland). Primary production and associated POC export from the photic zone showed marked seasonality, with annual integrated values of 7.2 and 19.9 mol C m-2 yr-1, respectively. This discrepancy, the isotopic signature, and C:N ratio of the sedimentating material suggested substantial import of marine POC from outside the fjord. At least 52% of the POC export reached the sediment, but the seasonality in pelagic productivity was not reflected in the sediment biogeochemistry, showing only moderate variation. Benthic mineralization and burial of organic carbon amounted to 3.2 and 5.3 mol C m-2 yr-1, respectively. Sulfate reduction was the most prominent mineralization pathway, accounting for 69% of the benthic mineralization, while denitrification accounted for 2%. Overall, the carbon mineralization and burial in Kobbefjord were significantly higher than previously observed in other more northerly Arctic fjords. Data compilation from Arctic fjords suggests proportional increases in surface production, POC export, benthic mineralization and burial of organic material with increasing duration of the ice-free period. Thus, the projected decline in ice coverage in higher Arctic Greenlandic fjords will, as a first approximation, entail proportional increases in productivity, mineralization, and burial of organic carbon in the fjords, which will thus become similar to present-day southerly systems.

KEY WORDS: Arctic · Climate changes · Primary production · POC export · Benthic biogeochemistry · Denitrification · Anammox · Sulfate reduction

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Cite this article as: Sørensen HL, Meire L, Juul-Pedersen T, de Stigter HC and others (2015) Seasonal carbon cycling in a Greenlandic fjord: an integrated pelagic and benthic study. Mar Ecol Prog Ser 539:1-17.

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