Nitrogen liberated via allelopathy can promote harmful algal blooms

Yoonja Kang; Christopher J Gobler

doi:10.1016/j.hal.2023.102490

Nitrogen liberated via allelopathy can promote harmful algal blooms

Harmful Algae. 2023 Nov:129:102490. doi: 10.1016/j.hal.2023.102490. Epub 2023 Sep 30.

Authors

Yoonja Kang¹, Christopher J Gobler²

Affiliations

¹ Chonnam National University, Department of Ocean Integrated Science, Yeosu 59626, South Korea.
² Stony Brook University, School of Marine and Atmospheric Sciences, Stony Brook, NY 11794, United States of America. Electronic address: christopher.gobler@stonybrook.edu.

PMID: 37951604
DOI: 10.1016/j.hal.2023.102490

Abstract

Allelopathy is a biological mechanism that can promote harmful algal blooms (HAB) via the inhibition of sympatric phytoplankton. While nutrient loading can also promote HABs, the ability of allelopathy to stimulate HABs via the regeneration of nutrients has yet to be explored. To examine the impacts of allelopathically liberated N on HAB species, a series of experiments were performed using multiple allelopathic HAB species including the dinoflagellates Alexandrium catenella and Margalefidinium polykrikoides, and the pelagophyte, Aureoumbra lagunensis. These HAB species were paired with the cosmopolitan dinoflagellate, Akashiwo sanguinea, that was labeled with ¹⁵NO₃^- or ¹⁵NH₄⁺, allowing the release and transfer of N to be traced as a time course during allelopathic interactions. During all experiments, the allelopathic inhibition of Akashiwo was accompanied by increases in cell densities, growth rates, and the δ¹⁵N content of the HAB species, evidencing the transfer of N liberated from Akashiwo. The cellular transfer of ¹⁵N and release of dissolved N was higher when Akashiwo was grown with ¹⁵NO₃^- compared to ¹⁵NH₄⁺ suggesting a differential subcellular-compartmentalization of N sources. Regardless of the type of N, HAB species obtained 60 - 100% of their cellular N from lysed Akashiwo cells and there was an enrichment of the δ¹⁵N content of the dissolved NH₄⁺ pool post-lysis of Akashiwo. Collectively, the results demonstrate that beyond facilitating species succession, allelopathy can supply HABs with N and, therefore, is likely important for promoting and sustaining HABs. Given that allelopathy is known to be a dose-dependent process, allelopathy may induce a positive feedback loop, whereby competitors are lysed, N is liberated, HABs are intensified and, in turn, become more strongly allelopathic.

Keywords: Akashiwo sanguinea; Alexandrium catenella; Allelopathy; Aureoumbra lagunensis; HABs; Margalefidinium polykrikoides; Regenerated nitrogen; Stable isotopes.

Publication types

Research Support, U.S. Gov't, Non-P.H.S.
Research Support, Non-U.S. Gov't

MeSH terms

Allelopathy
Dinoflagellida* / physiology
Harmful Algal Bloom* / physiology
Nitrogen
Phytoplankton

Substances

Nitrogen