Uptake of dissolved inorganic nitrogen and N2 fixation by Crocosphaera watsonii under climate change scenarios

The response of N2 fixation to projected future conditions in the ocean cannot be reliably predicted to date. We conducted a minicosm experiment with pre-acclimated cultures of the globally significant diazotroph Crocosphaera watsonii strain WH8501 (“Crocosphaera”). PH and temperature were altered s...

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Bibliographic Details
Published in:Frontiers in Marine Science
Main Authors: Jacqueline Umbricht, Alba Filella, Angelina Klett, Angela Vogts, Mar Benavides, Maren Voss
Format: Article in Journal/Newspaper
Language:English
Published: Frontiers Media S.A. 2024
Subjects:
nitrogen fixation
ocean warming
ocean acidification
nitrogen assimilation
Crocosphaera
minicosm experiment
Science
Q
General. Including nature conservation
geographical distribution
QH1-199.5
Ocean acidification
Online Access:https://doi.org/10.3389/fmars.2024.1388214
https://doaj.org/article/61e5a13bcbb8411495e499209a07e3cf
Description
Summary:The response of N2 fixation to projected future conditions in the ocean cannot be reliably predicted to date. We conducted a minicosm experiment with pre-acclimated cultures of the globally significant diazotroph Crocosphaera watsonii strain WH8501 (“Crocosphaera”). PH and temperature were altered simultaneously to match the RCP scenarios 4.5 and 6 and investigate a more realistic future scenario compared to studies that focus on changes of a single stressor only. The cell abundance and nitrogen metabolism of Crocosphaera was monitored over 5 days. Our results imply that Crocosphaera is able to simultaneously perform N2 fixation and assimilate dissolved inorganic nitrogen (DIN, i.e., nitrate and ammonium) under all the conditions tested and implies a competition with non-diazotrophic phytoplankton for DIN, which should be further investigated. Using NanoSIMS analysis of single cells, our results point towards a preference for DIN assimilation over N2 fixation under more acidic and warmer conditions. Overall, our results show that while the combined alteration of pH and temperature had a negative effect on the diazotroph’s growth and N2 fixation, Crocosphaera is likely to cope well with conditions in the future ocean. The high intra-population variability in nitrogen assimilation pathways may give this species the flexibility to quickly react to environmental changes.

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