Effects of CO2 on the nitrogen isotopic composition of Trichodesmium and Crocosphaera
Effects of CO2 on the nitrogen isotopic composition of Trichodesmium and Crocosphaera
Published 11 April 2024 Science Leave a CommentTags: biogeochemistry, biological response, chemistry, growth, laboratory, nitrogen fixation, physiology, prokaryotes
Biological nitrogen (N2) fixation is the main input of fixed nitrogen to ecosystems on Earth. Nitrogen isotope fractionation during this process is a key parameter for understanding the nitrogen cycle, however, relatively little is known about its regulatory mechanisms. Here we examine the effects of varying CO2 concentrations on biomass δ15N signatures of the cyanobacterial diazotrophs Trichodesmium erythraeum and Crocosphaera watsonii. We show that these organisms produce biomass up to ~3 ‰ lower in δ15N under either decreased (~180 µatm) or elevated (~1400 µatm) CO2 concentrations in comparison to modern levels (~380 µatm). Our results pointed towards changes in nitrogenase enzyme efficiency in response to CO2 perturbations impacting isotopic fractionation during N2 fixation and thus the biomass δ15N. This study contributes to an improved interpretation of the observed fluctuations in the δ15N records, and thus the past nitrogen cycle on Earth.
Wen Z., Jiang R., He T., Browning T., Hong H. & Shi D., 2024. Effects of CO2 on the nitrogen isotopic composition of Trichodesmium and Crocosphaera. EGUsphere. doi: 10.5194/egusphere-2024-775. Article.
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