Feeding-related controls on microbial nitrogen cycling associated with the Arctic marine copepod Calanus hyperboreus

Peter Stief, Ann Sofie Birch Lundgaard, Torkel Gissel Nielsen, Ronnie N. Glud

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Resumé

The copepod Calanus hyperboreus, a key species of Arctic marine ecosystems, has a partially anoxic gut that is suspected to host anaerobic microbial activities. So far, however, only dead specimens have been studied in which gut processes are quickly abolished by microbial carcass degradation. Here, live specimens were exposed to different feeding regimes and ambient oxygen levels to study the controls on copepod-associated microbial nitrogen cycling in 15N-enrichment experiments. Algae-fed copepods exhibited consistently high rates of denitrification and low or variable rates of dissimilatory nitrate reduction to ammonium (or nitrite), nitrification, and nitrous oxide release. Thus, live C. hyperboreus contribute to pelagic fixed-nitrogen loss through denitrification that is otherwise absent from oxygenated Arctic surface waters. The feeding-related controls on copepod-associated anaerobic nitrogen cycling are supported by significantly reduced rates in starved copepods. In addition, freshly released fecal pellets showed similar patterns of nitrogen cycling as fed copepods. Unlike in previous studies on copepod carcasses, low ambient oxygen levels did not stimulate anaerobic nitrogen cycling in live specimens, supporting that the C. hyperboreus gut is anoxic, irrespective of ambient oxygen levels. Fecal pellets and carcasses retained denitrification activity for 4 d of simulated sinking. We estimate that during the time of the Arctic spring bloom, pelagic denitrification associated with live specimens, fecal pellets, and carcasses of C. hyperboreus is equivalent to ~12% of the benthic fixed-nitrogen loss. This estimate increases to ~28%, provided that the abundant sibling species C. glacialis and C. finmarchicus exhibit denitrification activities in proportion to their smaller body size.
OriginalsprogEngelsk
TidsskriftMarine Ecology Progress Series
Vol/bind602
Sider (fra-til)1-14
ISSN0171-8630
DOI
StatusUdgivet - 23. aug. 2018

Fingeraftryk

Calanus
Arctic region
Copepoda
denitrification
fecal pellet
nitrogen
pellets
digestive system
oxygen
algae
nitrous oxide
nitrate reduction
marine ecosystem
sibling species
nitrite
microbial activity
nitrification
body size
algal bloom
nitrites

Citer dette

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title = "Feeding-related controls on microbial nitrogen cycling associated with the Arctic marine copepod Calanus hyperboreus",
abstract = "The copepod Calanus hyperboreus, a key species of Arctic marine ecosystems, has a partially anoxic gut that is suspected to host anaerobic microbial activities. So far, however, only dead specimens have been studied in which gut processes are quickly abolished by microbial carcass degradation. Here, live specimens were exposed to different feeding regimes and ambient oxygen levels to study the controls on copepod-associated microbial nitrogen cycling in 15N-enrichment experiments. Algae-fed copepods exhibited consistently high rates of denitrification and low or variable rates of dissimilatory nitrate reduction to ammonium (or nitrite), nitrification, and nitrous oxide release. Thus, live C. hyperboreus contribute to pelagic fixed-nitrogen loss through denitrification that is otherwise absent from oxygenated Arctic surface waters. The feeding-related controls on copepod-associated anaerobic nitrogen cycling are supported by significantly reduced rates in starved copepods. In addition, freshly released fecal pellets showed similar patterns of nitrogen cycling as fed copepods. Unlike in previous studies on copepod carcasses, low ambient oxygen levels did not stimulate anaerobic nitrogen cycling in live specimens, supporting that the C. hyperboreus gut is anoxic, irrespective of ambient oxygen levels. Fecal pellets and carcasses retained denitrification activity for 4 d of simulated sinking. We estimate that during the time of the Arctic spring bloom, pelagic denitrification associated with live specimens, fecal pellets, and carcasses of C. hyperboreus is equivalent to ~12{\%} of the benthic fixed-nitrogen loss. This estimate increases to ~28{\%}, provided that the abundant sibling species C. glacialis and C. finmarchicus exhibit denitrification activities in proportion to their smaller body size.",
author = "Peter Stief and Lundgaard, {Ann Sofie Birch} and Nielsen, {Torkel Gissel} and Glud, {Ronnie N.}",
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Feeding-related controls on microbial nitrogen cycling associated with the Arctic marine copepod Calanus hyperboreus. / Stief, Peter; Lundgaard, Ann Sofie Birch; Nielsen, Torkel Gissel; Glud, Ronnie N.

I: Marine Ecology Progress Series, Bind 602, 23.08.2018, s. 1-14.

Publikation: Bidrag til tidsskriftTidsskriftartikelForskningpeer review

TY - JOUR

T1 - Feeding-related controls on microbial nitrogen cycling associated with the Arctic marine copepod Calanus hyperboreus

AU - Stief, Peter

AU - Lundgaard, Ann Sofie Birch

AU - Nielsen, Torkel Gissel

AU - Glud, Ronnie N.

PY - 2018/8/23

Y1 - 2018/8/23

N2 - The copepod Calanus hyperboreus, a key species of Arctic marine ecosystems, has a partially anoxic gut that is suspected to host anaerobic microbial activities. So far, however, only dead specimens have been studied in which gut processes are quickly abolished by microbial carcass degradation. Here, live specimens were exposed to different feeding regimes and ambient oxygen levels to study the controls on copepod-associated microbial nitrogen cycling in 15N-enrichment experiments. Algae-fed copepods exhibited consistently high rates of denitrification and low or variable rates of dissimilatory nitrate reduction to ammonium (or nitrite), nitrification, and nitrous oxide release. Thus, live C. hyperboreus contribute to pelagic fixed-nitrogen loss through denitrification that is otherwise absent from oxygenated Arctic surface waters. The feeding-related controls on copepod-associated anaerobic nitrogen cycling are supported by significantly reduced rates in starved copepods. In addition, freshly released fecal pellets showed similar patterns of nitrogen cycling as fed copepods. Unlike in previous studies on copepod carcasses, low ambient oxygen levels did not stimulate anaerobic nitrogen cycling in live specimens, supporting that the C. hyperboreus gut is anoxic, irrespective of ambient oxygen levels. Fecal pellets and carcasses retained denitrification activity for 4 d of simulated sinking. We estimate that during the time of the Arctic spring bloom, pelagic denitrification associated with live specimens, fecal pellets, and carcasses of C. hyperboreus is equivalent to ~12% of the benthic fixed-nitrogen loss. This estimate increases to ~28%, provided that the abundant sibling species C. glacialis and C. finmarchicus exhibit denitrification activities in proportion to their smaller body size.

AB - The copepod Calanus hyperboreus, a key species of Arctic marine ecosystems, has a partially anoxic gut that is suspected to host anaerobic microbial activities. So far, however, only dead specimens have been studied in which gut processes are quickly abolished by microbial carcass degradation. Here, live specimens were exposed to different feeding regimes and ambient oxygen levels to study the controls on copepod-associated microbial nitrogen cycling in 15N-enrichment experiments. Algae-fed copepods exhibited consistently high rates of denitrification and low or variable rates of dissimilatory nitrate reduction to ammonium (or nitrite), nitrification, and nitrous oxide release. Thus, live C. hyperboreus contribute to pelagic fixed-nitrogen loss through denitrification that is otherwise absent from oxygenated Arctic surface waters. The feeding-related controls on copepod-associated anaerobic nitrogen cycling are supported by significantly reduced rates in starved copepods. In addition, freshly released fecal pellets showed similar patterns of nitrogen cycling as fed copepods. Unlike in previous studies on copepod carcasses, low ambient oxygen levels did not stimulate anaerobic nitrogen cycling in live specimens, supporting that the C. hyperboreus gut is anoxic, irrespective of ambient oxygen levels. Fecal pellets and carcasses retained denitrification activity for 4 d of simulated sinking. We estimate that during the time of the Arctic spring bloom, pelagic denitrification associated with live specimens, fecal pellets, and carcasses of C. hyperboreus is equivalent to ~12% of the benthic fixed-nitrogen loss. This estimate increases to ~28%, provided that the abundant sibling species C. glacialis and C. finmarchicus exhibit denitrification activities in proportion to their smaller body size.

U2 - 10.3354/meps12700

DO - 10.3354/meps12700

M3 - Journal article

VL - 602

SP - 1

EP - 14

JO - Marine Ecology - Progress Series

JF - Marine Ecology - Progress Series

SN - 0171-8630

ER -