ORIGINAL RESEARCH article
Front. Microbiol.
Sec. Aquatic Microbiology
Volume 16 - 2025 | doi: 10.3389/fmicb.2025.1663314
This article is part of the Research TopicMicrobial Influences on Coral Reef Resilience and RecoveryView all 5 articles
Ammonium supply represses iron limitation to support Symbiodiniaceae growth
Provisionally accepted
- 1Marine Science Institute, University of the Philippines Diliman, Quezon City, Philippines
- 2Bolinao Marine Laboratory, UP Marine Science Institute, Bolinao, Pangasinan, Philippines
- 3Department of Biology, SUNY College of Environmental Science and Forestry, Syracuse, United States
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Nutrient exchanges promote the success of symbioses among reef-building corals, endosymbiotic dinoflagellates (Family: Symbiodiniaceae), and their microbial symbionts. Nutrient dynamics has considerable implications on the metabolism and proliferation of the coral holobiont, with nutrient limitation known to increase the susceptibility of corals to bleaching by disrupting the host-symbiont nutrient exchange. This study examines how two Symbiodiniaceae species, Symbiodinium microadriaticum RT 362 and Cladocopium goreaui RT 152, respond to varying iron (Fe) availability, nitrate (NO3⁻), and ammonium (NH4+) in batch cultures. Under Fe limitation, phytoplankton growth is reduced when relying on NO₃⁻ due to the higher Fe requirement for nitrate assimilation enzymes, whereas NH4+ uptake is more efficient as it bypasses these Fe-dependent processes. Symbiodiniaceae utilize these nitrogenous compounds to fuel their metabolic processes, with an advantage in using NH4⁺ due to its greater energy efficiency and lower Fe requirement. Due to its role as cofactor of enzymes, Fe is crucial for nitrate reduction and chlorophyll synthesis, NH4+ assimilation remains effective even under low Fe conditions. The study reveals that in S. microadriaticum and C. goreaui, chlorophyll production, closely linked to Fe availability, significantly influences carbohydrate and lipid synthesis, with both species boosting protein and carotenoid production under low Fe conditions. Chlorophyll and the other photosynthetic macromolecule product concentrations continue to increase with NH4+ as the N source, even under low Fe conditions. These findings offer critical insights into how these species adapt to varying environmental conditions, improving our understanding of coral resilience.
Keywords: Trace metals, Nutrients, macromolecules, pigments, Algal symbionts, Microalgae
Received: 11 Jul 2025; Accepted: 13 Oct 2025.
Copyright: © 2025 Versola, Reich and Rodriguez. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Irene Barra Rodriguez, ibrodriguez@msi.upd.edu.ph
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