Impact of photo-chemical processing of DOC on the bacterioplankton respiratory quotient in aquatic ecosystems

Research output: Contribution to journalArticle


Many studies assume a respiratory quotient (RQ = molar ratio of CO2 produced to O2 consumed) close to 1 when calculating bacterioplankton respiration. However, evidence suggests that RQ depends on the chemical composition of the respired substrate pool that may be altered by photo-chemical production of oxygen-rich substrates, resulting in elevated RQs. Here we conducted a novel study of the impact of photo-chemical processing of dissolved organic carbon (DOC) on RQ. We monitored the bacterial RQ in bioassays of both ultraviolet light irradiated and non-irradiated humic lake water, using optic gas-pressure sensors. In the experimentally irradiated samples the average RQ value was significantly higher (3.4-3.5 [± 0.4 s.e.]) than that in the dark controls (1.3 [± 0.1 s.e.]). Our results show that the RQ is systematically higher than 1 when the bacterial metabolism in large part is based on photo-products. By assuming an RQ of 1, bacterioplankton respiration in freshwater ecosystems may be greatly underestimated.


External organisations
  • University of Oslo
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Earth and Related Environmental Sciences
Original languageEnglish
Pages (from-to)7538–7545
Number of pages8
JournalGeophysical Research Letters
Issue number14
Early online date2016 Jun 29
Publication statusPublished - 2016 Jul 28
Publication categoryResearch