Macrofauna regulate heterotrophic bacterial carbon and nitrogen incorporation in low-oxygen sediments

William R. Hunter, Bart Veuger, Ursula Witte

Research output: Contribution to journalArticle

13 Citations (Scopus)

Abstract

Oxygen minimum zones (OMZs) currently impinge upon >1 million km 2 of sea floor and are predicted to expand with climate change. We investigated how changes in oxygen availability, macrofaunal biomass and retention of labile organic matter (OM) regulate heterotrophic bacterial C and N incorporation in the sediments of the OMZ-impacted Indian continental margin (540-1100 m; O 2 0.35-15 μmol l 1). In situ pulse-chase experiments traced 13 C: 15 N-labelled phytodetritus into bulk sediment OM and hydrolysable amino acids, including the bacterial biomarker D-alanine. Where oxygen availability was lowest (O 2 0.35 μmol l 1), metazoan macrofauna were absent and bacteria assimilated 30-90% of the labelled phytodetritus within the sediment. At higher oxygen levels (O 2 2-15 μmol l 1) the macrofaunal presence and lower phytodetritus retention with the sediment occur concomitantly, and bacterial phytodetrital incorporation was reduced and retarded. Bacterial C and N incorporation exhibited a significant negative relationship with macrofaunal biomass across the OMZ. We hypothesise that fauna-bacterial interactions significantly influence OM recycling in low-oxygen sediments and need to be considered when assessing the consequences of global change on biogeochemical cycles.
LanguageUndefined
Pages2140-2151
Number of pages12
JournalThe ISME journal
Volume6
Issue number11
DOIs
Publication statusPublished - 17 May 2012

Keywords

  • bacteria, C:N coupling, hydrolysable amino acids, macrofauna, oxygen minimum zone, sediment

Cite this

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abstract = "Oxygen minimum zones (OMZs) currently impinge upon >1 million km 2 of sea floor and are predicted to expand with climate change. We investigated how changes in oxygen availability, macrofaunal biomass and retention of labile organic matter (OM) regulate heterotrophic bacterial C and N incorporation in the sediments of the OMZ-impacted Indian continental margin (540-1100 m; O 2 0.35-15 μmol l 1). In situ pulse-chase experiments traced 13 C: 15 N-labelled phytodetritus into bulk sediment OM and hydrolysable amino acids, including the bacterial biomarker D-alanine. Where oxygen availability was lowest (O 2 0.35 μmol l 1), metazoan macrofauna were absent and bacteria assimilated 30-90{\%} of the labelled phytodetritus within the sediment. At higher oxygen levels (O 2 2-15 μmol l 1) the macrofaunal presence and lower phytodetritus retention with the sediment occur concomitantly, and bacterial phytodetrital incorporation was reduced and retarded. Bacterial C and N incorporation exhibited a significant negative relationship with macrofaunal biomass across the OMZ. We hypothesise that fauna-bacterial interactions significantly influence OM recycling in low-oxygen sediments and need to be considered when assessing the consequences of global change on biogeochemical cycles.",
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Macrofauna regulate heterotrophic bacterial carbon and nitrogen incorporation in low-oxygen sediments. / Hunter, William R.; Veuger, Bart; Witte, Ursula.

In: The ISME journal, Vol. 6, No. 11, 17.05.2012, p. 2140-2151.

Research output: Contribution to journalArticle

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AU - Veuger, Bart

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N2 - Oxygen minimum zones (OMZs) currently impinge upon >1 million km 2 of sea floor and are predicted to expand with climate change. We investigated how changes in oxygen availability, macrofaunal biomass and retention of labile organic matter (OM) regulate heterotrophic bacterial C and N incorporation in the sediments of the OMZ-impacted Indian continental margin (540-1100 m; O 2 0.35-15 μmol l 1). In situ pulse-chase experiments traced 13 C: 15 N-labelled phytodetritus into bulk sediment OM and hydrolysable amino acids, including the bacterial biomarker D-alanine. Where oxygen availability was lowest (O 2 0.35 μmol l 1), metazoan macrofauna were absent and bacteria assimilated 30-90% of the labelled phytodetritus within the sediment. At higher oxygen levels (O 2 2-15 μmol l 1) the macrofaunal presence and lower phytodetritus retention with the sediment occur concomitantly, and bacterial phytodetrital incorporation was reduced and retarded. Bacterial C and N incorporation exhibited a significant negative relationship with macrofaunal biomass across the OMZ. We hypothesise that fauna-bacterial interactions significantly influence OM recycling in low-oxygen sediments and need to be considered when assessing the consequences of global change on biogeochemical cycles.

AB - Oxygen minimum zones (OMZs) currently impinge upon >1 million km 2 of sea floor and are predicted to expand with climate change. We investigated how changes in oxygen availability, macrofaunal biomass and retention of labile organic matter (OM) regulate heterotrophic bacterial C and N incorporation in the sediments of the OMZ-impacted Indian continental margin (540-1100 m; O 2 0.35-15 μmol l 1). In situ pulse-chase experiments traced 13 C: 15 N-labelled phytodetritus into bulk sediment OM and hydrolysable amino acids, including the bacterial biomarker D-alanine. Where oxygen availability was lowest (O 2 0.35 μmol l 1), metazoan macrofauna were absent and bacteria assimilated 30-90% of the labelled phytodetritus within the sediment. At higher oxygen levels (O 2 2-15 μmol l 1) the macrofaunal presence and lower phytodetritus retention with the sediment occur concomitantly, and bacterial phytodetrital incorporation was reduced and retarded. Bacterial C and N incorporation exhibited a significant negative relationship with macrofaunal biomass across the OMZ. We hypothesise that fauna-bacterial interactions significantly influence OM recycling in low-oxygen sediments and need to be considered when assessing the consequences of global change on biogeochemical cycles.

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