Sinking krill carcasses as hotspots of microbial carbon and nitrogen cycling in the Arctic
Krill represent a major link between primary producers and higher trophic levels in polar marine food webs. Potential links to lower trophic levels, such as heterotrophic microorganisms, are less well documented. Here, we studied the kinetics of microbial degradation of sinking carcasses of two domi...
Published in: | Frontiers in Marine Science |
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Online Access: | https://doi.org/10.3389/fmars.2022.1019727 https://doaj.org/article/823d24b72de94b1dbab2172908b55434 |
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ftdoajarticles:oai:doaj.org/article:823d24b72de94b1dbab2172908b55434 2023-05-15T15:00:46+02:00 Sinking krill carcasses as hotspots of microbial carbon and nitrogen cycling in the Arctic Belén Franco-Cisterna Anni Glud Laura A. Bristow Arka Rudra Hamed Sanei Mie H.S. Winding Torkel G. Nielsen Ronnie N. Glud Peter Stief 2022-11-01T00:00:00Z https://doi.org/10.3389/fmars.2022.1019727 https://doaj.org/article/823d24b72de94b1dbab2172908b55434 EN eng Frontiers Media S.A. https://www.frontiersin.org/articles/10.3389/fmars.2022.1019727/full https://doaj.org/toc/2296-7745 2296-7745 doi:10.3389/fmars.2022.1019727 https://doaj.org/article/823d24b72de94b1dbab2172908b55434 Frontiers in Marine Science, Vol 9 (2022) Biological carbon pump marine snow nitrogen carbon oxygen krill Science Q General. Including nature conservation geographical distribution QH1-199.5 article 2022 ftdoajarticles https://doi.org/10.3389/fmars.2022.1019727 2022-12-30T21:38:19Z Krill represent a major link between primary producers and higher trophic levels in polar marine food webs. Potential links to lower trophic levels, such as heterotrophic microorganisms, are less well documented. Here, we studied the kinetics of microbial degradation of sinking carcasses of two dominant krill species Thysanoessa raschii and Meganyctiphanes norvegica from Southwest Greenland. Degradation experiments under oxic conditions showed that 6.0-9.1% of carbon and 6.4-7.1% of nitrogen were lost from the carcasses after one week. Aerobic microbial respiration and the release of dissolved organic carbon were the main pathways of carbon loss from the carcasses. Ammonium release generally contributed the most to carcass nitrogen loss. Oxygen micro profiling revealed anoxic conditions inside krill carcasses/specimens, allowing anaerobic nitrogen cycling through denitrification and dissimilatory nitrate reduction to ammonium (DNRA). Denitrification rates were up to 5.3 and 127.7 nmol N carcass-1 d-1 for T. raschii and M. norvegica, respectively, making krill carcasses hotspots of nitrogen loss in the oxygenated water column of the fjord. Carcass-associated DNRA rates were up to 4-fold higher than denitrification rates, but the combined activity of these two anaerobic respiration processes did not contribute significantly to carbon loss from the carcasses. Living krill specimens did not harbor any significant denitrification and DNRA activity despite having an anoxic gut as revealed by micro profiling. The investigated krill carcasses sink fast (1500-3000 m d-1) and our data show that only a small fraction of the associated carbon is lost during descent. Based on data on krill distribution, our findings are used to discuss the potential importance of sinking krill carcasses for sustaining benthic food webs in the Arctic. Article in Journal/Newspaper Arctic Greenland Meganyctiphanes norvegica Thysanoessa raschii Directory of Open Access Journals: DOAJ Articles Arctic Greenland Frontiers in Marine Science 9 |
institution |
Open Polar |
collection |
Directory of Open Access Journals: DOAJ Articles |
op_collection_id |
ftdoajarticles |
language |
English |
topic |
Biological carbon pump marine snow nitrogen carbon oxygen krill Science Q General. Including nature conservation geographical distribution QH1-199.5 |
spellingShingle |
Biological carbon pump marine snow nitrogen carbon oxygen krill Science Q General. Including nature conservation geographical distribution QH1-199.5 Belén Franco-Cisterna Anni Glud Laura A. Bristow Arka Rudra Hamed Sanei Mie H.S. Winding Torkel G. Nielsen Ronnie N. Glud Peter Stief Sinking krill carcasses as hotspots of microbial carbon and nitrogen cycling in the Arctic |
topic_facet |
Biological carbon pump marine snow nitrogen carbon oxygen krill Science Q General. Including nature conservation geographical distribution QH1-199.5 |
description |
Krill represent a major link between primary producers and higher trophic levels in polar marine food webs. Potential links to lower trophic levels, such as heterotrophic microorganisms, are less well documented. Here, we studied the kinetics of microbial degradation of sinking carcasses of two dominant krill species Thysanoessa raschii and Meganyctiphanes norvegica from Southwest Greenland. Degradation experiments under oxic conditions showed that 6.0-9.1% of carbon and 6.4-7.1% of nitrogen were lost from the carcasses after one week. Aerobic microbial respiration and the release of dissolved organic carbon were the main pathways of carbon loss from the carcasses. Ammonium release generally contributed the most to carcass nitrogen loss. Oxygen micro profiling revealed anoxic conditions inside krill carcasses/specimens, allowing anaerobic nitrogen cycling through denitrification and dissimilatory nitrate reduction to ammonium (DNRA). Denitrification rates were up to 5.3 and 127.7 nmol N carcass-1 d-1 for T. raschii and M. norvegica, respectively, making krill carcasses hotspots of nitrogen loss in the oxygenated water column of the fjord. Carcass-associated DNRA rates were up to 4-fold higher than denitrification rates, but the combined activity of these two anaerobic respiration processes did not contribute significantly to carbon loss from the carcasses. Living krill specimens did not harbor any significant denitrification and DNRA activity despite having an anoxic gut as revealed by micro profiling. The investigated krill carcasses sink fast (1500-3000 m d-1) and our data show that only a small fraction of the associated carbon is lost during descent. Based on data on krill distribution, our findings are used to discuss the potential importance of sinking krill carcasses for sustaining benthic food webs in the Arctic. |
format |
Article in Journal/Newspaper |
author |
Belén Franco-Cisterna Anni Glud Laura A. Bristow Arka Rudra Hamed Sanei Mie H.S. Winding Torkel G. Nielsen Ronnie N. Glud Peter Stief |
author_facet |
Belén Franco-Cisterna Anni Glud Laura A. Bristow Arka Rudra Hamed Sanei Mie H.S. Winding Torkel G. Nielsen Ronnie N. Glud Peter Stief |
author_sort |
Belén Franco-Cisterna |
title |
Sinking krill carcasses as hotspots of microbial carbon and nitrogen cycling in the Arctic |
title_short |
Sinking krill carcasses as hotspots of microbial carbon and nitrogen cycling in the Arctic |
title_full |
Sinking krill carcasses as hotspots of microbial carbon and nitrogen cycling in the Arctic |
title_fullStr |
Sinking krill carcasses as hotspots of microbial carbon and nitrogen cycling in the Arctic |
title_full_unstemmed |
Sinking krill carcasses as hotspots of microbial carbon and nitrogen cycling in the Arctic |
title_sort |
sinking krill carcasses as hotspots of microbial carbon and nitrogen cycling in the arctic |
publisher |
Frontiers Media S.A. |
publishDate |
2022 |
url |
https://doi.org/10.3389/fmars.2022.1019727 https://doaj.org/article/823d24b72de94b1dbab2172908b55434 |
geographic |
Arctic Greenland |
geographic_facet |
Arctic Greenland |
genre |
Arctic Greenland Meganyctiphanes norvegica Thysanoessa raschii |
genre_facet |
Arctic Greenland Meganyctiphanes norvegica Thysanoessa raschii |
op_source |
Frontiers in Marine Science, Vol 9 (2022) |
op_relation |
https://www.frontiersin.org/articles/10.3389/fmars.2022.1019727/full https://doaj.org/toc/2296-7745 2296-7745 doi:10.3389/fmars.2022.1019727 https://doaj.org/article/823d24b72de94b1dbab2172908b55434 |
op_doi |
https://doi.org/10.3389/fmars.2022.1019727 |
container_title |
Frontiers in Marine Science |
container_volume |
9 |
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1766332839377240064 |