Combined effects of different CO2 levels and N sources on the diazotrophic cyanobacterium Trichodesmium
Article first published online: 26 MAR 2014
© 2014 The Authors. Physiologia Plantarum published by John Wiley & Sons Ltd on behalf of Scandinavian Plant Physiology Society.
This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.
Volume 152, Issue 2, pages 316–330, October 2014
How to Cite
Eichner, M., Kranz, S. A. and Rost, B. (2014), Combined effects of different CO2 levels and N sources on the diazotrophic cyanobacterium Trichodesmium. Physiologia Plantarum, 152: 316–330. doi: 10.1111/ppl.12172
- Issue published online: 16 SEP 2014
- Article first published online: 26 MAR 2014
- Accepted manuscript online: 18 FEB 2014 12:12PM EST
- Manuscript Accepted: 21 JAN 2014
- Manuscript Revised: 17 JAN 2014
- Manuscript Received: 11 NOV 2013
- European Research Council. Grant Numbers: FP7/2007-2013, 205150
To predict effects of climate change and possible feedbacks, it is crucial to understand the mechanisms behind CO2 responses of biogeochemically relevant phytoplankton species. Previous experiments on the abundant N2 fixers Trichodesmium demonstrated strong CO2 responses, which were attributed to an energy reallocation between its carbon (C) and nitrogen (N) acquisition. Pursuing this hypothesis, we manipulated the cellular energy budget by growing Trichodesmium erythraeum IMS101 under different CO2 partial pressure (pCO2) levels (180, 380, 980 and 1400 µatm) and N sources (N2 and NO3−). Subsequently, biomass production and the main energy-generating processes (photosynthesis and respiration) and energy-consuming processes (N2 fixation and C acquisition) were measured. While oxygen fluxes and chlorophyll fluorescence indicated that energy generation and its diurnal cycle was neither affected by pCO2 nor N source, cells differed in production rates and composition. Elevated pCO2 increased N2 fixation and organic C and N contents. The degree of stimulation was higher for nitrogenase activity than for cell contents, indicating a pCO2 effect on the transfer efficiency from N2 to biomass. pCO2-dependent changes in the diurnal cycle of N2 fixation correlated well with C affinities, confirming the interactions between N and C acquisition. Regarding effects of the N source, production rates were enhanced in NO3− grown cells, which we attribute to the higher N retention and lower ATP demand compared with N2 fixation. pCO2 effects on C affinity were less pronounced in NO3− users than N2 fixers. Our study illustrates the necessity to understand energy budgets and fluxes under different environmental conditions for explaining indirect effects of rising pCO2.