In:
The ISME Journal, Springer Science and Business Media LLC, Vol. 16, No. 2 ( 2022-02), p. 477-487
Abstract:
N 2 fixation constitutes an important new nitrogen source in the open sea. One group of filamentous N 2 fixing cyanobacteria ( Richelia intracellularis , hereafter Richelia) form symbiosis with a few genera of diatoms. High rates of N 2 fixation and carbon (C) fixation have been measured in the presence of diatom- Richelia symbioses. However, it is unknown how partners coordinate C fixation and how the symbiont sustains high rates of N 2 fixation. Here, both the N 2 and C fixation in wild diatom- Richelia populations are reported. Inhibitor experiments designed to inhibit host photosynthesis, resulted in lower estimated growth and depressed C and N 2 fixation, suggesting that despite the symbionts ability to fix their own C, they must still rely on their respective hosts for C. Single cell analysis indicated that up to 22% of assimilated C in the symbiont is derived from the host, whereas 78–91% of the host N is supplied from their symbionts. A size-dependent relationship is identified where larger cells have higher N 2 and C fixation, and only N 2 fixation was light dependent. Using the single cell measures, the N-rich phycosphere surrounding these symbioses was estimated and contributes directly and rapidly to the surface ocean rather than the mesopelagic, even at high estimated sinking velocities ( 〈 10 m d −1 ). Several eco-physiological parameters necessary for incorporating symbiotic N 2 fixing populations into larger basin scale biogeochemical models (i.e., N and C cycles) are provided.
Type of Medium:
Online Resource
ISSN:
1751-7362
,
1751-7370
DOI:
10.1038/s41396-021-01086-7
Language:
English
Publisher:
Springer Science and Business Media LLC
Publication Date:
2022
detail.hit.zdb_id:
2299378-2
