Symbiotic UCYN-A Strains Co-occurred with El Niño, Relaxed Upwelling, and Varied Eukaryotes Over 10 Years Off Southern California

Authors

Colette Fletcher-Hoppe, University of Southern California
Yi-Chun Yeh, University of Southern California
Yubin Raut, University of Southern California
J. L. Weissman, Chapman UniversityFollow
Jed A. Fuhrman, University of Southern CaliforniaFollow

Document Type

Article

Publication Date

6-24-2023

Abstract

Biological nitrogen fixation, the conversion of N₂ gas into a bioavailable form, is vital to sustaining marine primary production. Studies have shifted beyond traditionally studied tropical diazotrophs. Candidatus Atelocyanobacterium thalassa (or UCYN-A) has emerged as a focal point due to its streamlined metabolism, intimate partnership with a haptophyte host, and broad distribution. Here, we explore the environmental parameters that govern UCYN-A’s presence at the San Pedro Ocean Time-series (SPOT), its host specificity, and statistically significant interactions with non-host eukaryotes from 2008-2018. 16S and 18S rRNA gene sequences were amplified by “universal primers” from monthly samples and resolved into Amplicon Sequence Variants, allowing us to observe multiple UCYN-A symbioses. UCYN-A1 relative abundances increased following the 2015-2016 El Niño event. This “open ocean ecotype” was present when coastal upwelling declined, and Ekman transport brought tropical waters into the region. Network analyses reveal all strains of UCYN-A co-occur with dinoflagellates including Lepidodinium, a potential predator, and parasitic Syndiniales. UCYN-A2 appeared to pair with multiple hosts and was not tightly coupled to its predominant host, while UCYN-A1 maintained a strong host-symbiont relationship. These biological relationships are particularly important to study in the context of climate change, which will alter UCYN-A distribution at regional and global scales.

Comments

This article was originally published in ISME Communications, volume 3, in 2023. https://doi.org/10.1038/s43705-023-00268-y

Recommended Citation

Fletcher-Hoppe, C., Yeh, YC., Raut, Y. et al. Symbiotic UCYN-A strains co-occurred with El Niño, relaxed upwelling, and varied eukaryotes over 10 years off Southern California. ISME COMMUN. 3, 63 (2023). https://doi.org/10.1038/s43705-023-00268-y

Copyright

The authors

Creative Commons License

This work is licensed under a Creative Commons Attribution 4.0 License.