Short-term processing of ice algal- and phytoplankton-derived carbon by Arctic benthic communities revealed through isotope labelling experiments

Anni Mäkelä, Ursula Witte, Philippe Archambault

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Abstract

Benthic ecosystems play a significant role in the carbon (C) cycle through remineralization of organic matter reaching the seafloor. Ice algae and phytoplankton are major C sources for Arctic benthic consumers, but climate change-mediated loss of summer sea ice is predicted to change Arctic marine primary production by increasing phytoplankton and reducing ice algal contributions. To investigate the impact of changing algal C sources on benthic C processing, 2 isotope tracing experiments on 13C-labelled ice algae and phytoplankton were conducted in the North Water Polynya (NOW; 709 m depth) and Lancaster Sound (LS; 794 m) in the Canadian Arctic, during which the fate of ice algal (CIA) and phytoplankton (CPP) C added to sediment cores was traced over 4 d. No difference in sediment community oxygen consumption (SCOC, indicative of total C turnover) between the background measurements and ice algal or phytoplankton cores was found at either site. Most of the processed algal C was respired, with significantly more CPP than CIA being released as dissolved inorganic C at both sites. Macroinfaunal uptake of algal C was minor, but bacterial assimilation accounted for 33-44% of total algal C processing, with no differences in bacterial uptake of CPP and CIA found at either site. Overall, the total processing (i.e. assimilation and respiration) of CPP was 33 and 37% higher than processing of CIA in NOW and in LS, respectively, suggesting that the future changes in quality of organic matter sinking to the seafloor could impact the C residence time at the seafloor.
Original languageEnglish
Pages (from-to)21-39
Number of pages19
JournalMarine Ecology Progress Series
Volume600
Early online date30 Jul 2018
DOIs
Publication statusPublished - 2018

Keywords

  • Arctic
  • carbon cycling
  • sediment
  • respiration
  • 13C
  • bacteria
  • Benthic-pelagic coupling
  • sea ice cover

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