Toxic Effects and Ecophysiology of Algal Blooms

Harmful algal blooms represent episodic surges in microalgal biomass that disrupt aquatic ecosystems, economies and public health on a global scale. Central to these events are toxic species such as the golden alga Prymnesium parvum, whose secreted metabolites impair gill function in fish, provoke cell lysis in non‐target organisms and can even affect human epithelial tissues. Bloom formation is governed by a suite of ecophysiological traits, including mixotrophy, whereby cells supplement photosynthesis with phagotrophy, and finely tuned responses to nutrient regimes, salinity gradients and light availability. Under nutrient imbalance or stress, many bloom‐forming species upregulate polyketide synthase pathways, leading to enhanced secondary metabolite production. These toxins often interact directly with plasma membranes, causing ion leakage, osmotic imbalance and oxidative stress. In parallel, allelopathic interactions suppress competing phytoplankton, reinforcing bloom dominance. The interplay of hydrodynamics, temperature shifts and anthropogenic eutrophication further modulates bloom intensity and duration. Contemporary research is extending our understanding of genetic underpinnings, environmental triggers and mechanistic toxicity, in order to refine predictive models and to develop targeted mitigation strategies that balance ecological integrity with water‐use demands.

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Toxic Effects and Ecophysiology of Algal Blooms publication trend

The graph below shows the total number of articles in toxic effects and ecophysiology of algal blooms across all publications each year (not limited to Nature Index journals).

Technical terms

Harmful algal bloom: A rapid proliferation of algae or cyanobacteria that produces toxins or depletes oxygen, causing ecological and economic damage.

Prymnesins: A family of ladder‐frame polyether toxins produced by Prymnesium parvum, varying in backbone structure and substituents.

Mixotrophy: A nutritional strategy combining autotrophic photosynthesis with heterotrophic ingestion of organic particles.

Polyketide synthase (PKS): A modular enzyme complex responsible for the assembly of polyketide secondary metabolites, including algal toxins.

Ichthyotoxic: Exhibiting toxic effects specifically towards fish, often via gill damage or respiratory impairment.

Eutrophication: The enrichment of water bodies with nutrients such as nitrogen and phosphorus, leading to excessive algal growth.

References

1. Long-read genome sequencing provides novel insights into the harmful algal bloom species Prymnesium parvum. The Science of The Total Environment (2023).
2. Cytotoxicity of Prymnesium parvum extracts and prymnesin analogs on epithelial fish gill cells RTgill-W1 and the human colon cell line HCEC-1CT. Archives of Toxicology (2024).
3. Influence of biotic and abiotic factors on prymnesin profiles in three strains of Prymnesium parvum. Algal Research (2024).
4. Polyketide synthase genes and molecular trade-offs in the ichthyotoxic species Prymnesium parvum. The Science of The Total Environment (2021).