High plasticity of nitrogen fixation and denitrification of common coral reef substrates in response to nitrate availability

Yusuf C. El-Khaled, Rassil Nafeh, Florian Roth, Nils Radecker, Denis B. Karcher, Burton Jones, Christian R. Voolstra, Christian Wild

Research output: Contribution to journalArticlepeer-review

Abstract

Nitrogen cycling in coral reefs may be affected by nutrient availability, but knowledge about concentration-dependent thresholds that modulate dinitrogen fixation and denitrification is missing. We determined the effects of different nitrate concentrations (ambient, 1, 5, 10 μM nitrate addition) on both processes under two light scenarios (i.e., light and dark) using a combined acetylene assay for two common benthic reef substrates, i.e., turf algae and coral rubble. For both substrates, dinitrogen fixation rates peaked at 5 μM nitrate addition in light, whereas denitrification was highest at 10 μM nitrate addition in the dark. At 10 μm nitrate addition in the dark, a near-complete collapse of dinitrogen fixation concurrent with a 76-fold increase in denitrification observed for coral rubble, suggesting potential threshold responses linked to the nutritional state of the community. We conclude that dynamic nitrogen cycling activity may help stabilise nitrogen availability in microbial communities associated with coral reef substrates.
Original languageEnglish (US)
Pages (from-to)112430
JournalMarine Pollution Bulletin
Volume168
DOIs
StatePublished - May 14 2021

ASJC Scopus subject areas

  • Oceanography
  • Pollution
  • Aquatic Science

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