Microbial Interactions in Harmful Algal Blooms

Marine harmful algal blooms arise when toxin‐producing phytoplankton proliferate, with microbial partners both sustaining and inhibiting bloom development. Within the phycosphere, bacteria, viruses and protozoa engage in mutualism, competition and parasitism that shape nutrient cycling, toxin production and bloom longevity. Heterotrophic bacteria scavenge organic matter released by algae, driving carbon and nitrogen turnover, while specialised lineages secrete siderophores to supply iron or degrade algal metabolites. Viral infections modulate bacterial abundances and can trigger microbial succession that influences bloom decline. Chemical communication between dinoflagellates and bacterial consortia alters toxin profiles, whereas protistan grazers regulate algal biomass. Collectively, these interactions underpin biogeochemical fluxes, mediate ecological resilience and inform strategies for bloom prediction and mitigation. Understanding the dynamic interplay among microbes in harmful algal blooms is critical for anticipating ecosystem responses to climate‐driven changes and for safeguarding public health and marine resources.

Research from Nature Portfolio

Recent studies have contrasted bacterial communities in the microenvironment of toxic versus non‐toxic dinoflagellates, revealing that toxin‐producing species are associated with specialised taxa capable of xenobiotic degradation and suppression of algicidal bacteria. This discovery emphasises the role of the phycosphere in promoting bloom persistence and toxicity. In parallel, controlled microcosm experiments tracking an Akashiwo sanguinea bloom demonstrated that bacterial assemblages shift from flourishers of chemoheterotrophy during peak algal growth to nitrogen‐cycling specialists during decline. Functional gene analysis showed a rapid turnover of metabolic pathways in response to nutrient influx, highlighting the tight coupling between algal physiology and bacterial function throughout bloom succession.

Microbial Interactions in Harmful Algal Blooms publication trend

The graph below shows the total number of articles in microbial interactions in harmful algal blooms across all publications each year (not limited to Nature Index journals).

Technical terms

Phycosphere: The immediate microenvironment surrounding algal cells, where intense microbial interactions occur.

Metagenomics: A culture‐independent approach to analyse the collective genetic material of environmental microbial communities.

Microbiome: The assemblage of microorganisms and their genomes within a defined habitat.

Siderophore: A specialised molecule secreted by microbes to bind and solubilise iron for uptake.

Chemoheterotrophy: Metabolism in which organisms obtain energy and carbon by consuming organic compounds.

Dissolved organic matter (DOM): Organic molecules in water released by organisms, serving as nutrient substrates for microbes.

References

1. Toxic and non-toxic dinoflagellates host distinct bacterial communities in their phycospheres. Communications Earth & Environment (2023).
2. Dynamic bacterial community response to Akashiwo sanguinea (Dinophyceae) bloom in indoor marine microcosms. Scientific Reports (2021).
3. Taxonomic difference in marine bloom-forming phytoplanktonic species affects the dynamics of both bloom-responding prokaryotes and prokaryotic viruses. mSystems (2024).
4. Dinoflagellate–Bacteria Interactions: Physiology, Ecology, and Evolution. Biology (2024).
5. Characterizing the Influence of a Heterotrophic Bicosoecid Flagellate Pseudobodo sp. on the Dinoflagellate Gambierdiscus balechii. Toxins (2023).