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

Summary, in English

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.

• Author: Lina Allesson; Lena Ström; Martin Berggren
• Department/s: Dept of Physical Geography and Ecosystem Science; BECC: Biodiversity and Ecosystem services in a Changing Climate
• Publishing year: 2016-07-28
• Language: English
• Pages: 7538-7545
• Publication/Series: Geophysical Research Letters
• Volume: 43
• Issue: 14
• Links: http://dx.doi.org/10.1002/2016GL069621
• Document type: Journal article
• Publisher: American Geophysical Union (AGU)
• Topic: Earth and Related Environmental Sciences
• Status: Published
• ISBN/ISSN/Other: ISSN: 1944-8007