Heterotrophic Nitrogen Fixation at the Hyper-Eutrophic Qishon River and Estuary System

Eyal Geisler, Anne Bogler, Edo Bar-Zeev, Eyal Rahav

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16 Scopus citations


Planktonic heterotrophic diazotrophs (N2-fixers) are widely distributed in marine and freshwater systems, yet limited information is available on their activity, especially in environments with adverse conditions for diazotrophy (e.g., N-rich and oxygenated). Here, we followed the localization and activity of heterotrophic diazotrophs in the hyper-eutrophic N-rich Qishon River—an environment previously considered to be unfavorable for diazotrophy. Our results indicate high heterotrophic N2 fixation rates (up to 6.9 nmol N L–1 d–1), which were approximately three fold higher at an upstream location (freshwater) compared to an estuary (brackish) site. Further, active heterotrophic diazotrophs were capture associated with free-floating aggregates by a newly developed immunolocalization approach. These findings provide new insights on the activity of heterotrophic diazotrophs on aggregates in environments previously considered with adverse conditions for diazotrophy. Moreover, these new insights may be applicable to other aquatic regimes worldwide with similar N-rich/oxygenated conditions that should potentially inhibit N2 fixation.

Original languageEnglish
Article number1370
JournalFrontiers in Microbiology
StatePublished - 24 Jun 2020
Externally publishedYes

Bibliographical note

Publisher Copyright:
© Copyright © 2020 Geisler, Bogler, Bar-Zeev and Rahav.


We would like to thank the Qishon Water Authority for providing nutrient load values. We would also like to express our gratitude to the Yohai Ben-Nun and the Negev scholarships to EG. This article is in partial fulfillment of the Ph.D. thesis by EG at Ben-Gurion University of the Negev. Funding. This study was partly supported by the Israeli Monitoring Program (Ministry of Environmental Protection and Ministry of Energy), the Roy J. Zuckerberg Foundation, and the Israel Science Foundation (grant #1211/17).

FundersFunder number
Ministry of Energy
Ministry of Environmental Protection
Qishon Water Authority
Roy J. Zuckerberg Foundation
Israel Science Foundation1211/17


    • N fixation
    • aggregates
    • estuary
    • nitrogenase immunolocalization
    • polysaccharides


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