Mitigation Strategies for Harmful Algal Blooms

Harmful algal blooms (HABs) pose a growing threat to aquatic ecosystems, public health and coastal economies worldwide. Mitigation approaches fall broadly into physical, chemical and biological categories, often integrated to maximise efficacy and minimise collateral effects. Physical removal techniques include flocculation and sedimentation, with a particular focus on modified clays that aggregate algal cells to enhance natural settling. Chemical strategies aim to disrupt algal metabolism or remove limiting nutrients, notably phosphorus and nitrogen, through adsorptive materials or nutrient-binding agents. Biological controls exploit natural predators, pathogens or competitive species to suppress bloom-forming taxa. Innovations in photocatalysis and surface-engineered materials offer targeted algal deactivation by generating reactive species under illumination, while mesocosm experiments and field trials increasingly inform safe application rates and ecological impacts. A growing emphasis on ecosystem-based management advocates pre-emptive nutrient reduction and habitat restoration to reduce bloom frequency and severity. Together, these approaches underscore the importance of combined, site-specific strategies that balance rapid bloom suppression with long-term ecosystem resilience.

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Mitigation Strategies for Harmful Algal Blooms publication trend

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

Technical terms

Flocculation: The process by which particles aggregate into larger flocs, facilitating their sedimentation and removal from the water column.

Modified clay: A natural clay mineral chemically treated to enhance its adsorption capacity and flocculation efficiency for algal cells and nutrients.

Dissolved algal organic matter (dAOM): Organic compounds released by algal cells that influence water chemistry and the aggregation behaviour of suspended particles.

Biocontrol agent: A living organism or virus deployed to selectively infect or graze upon harmful algae, reducing bloom intensity without broad ecological disruption.

Mesocosm: A controlled outdoor experimental system that simulates natural environmental conditions to test ecological interactions and treatment efficacy.

References

1. Mesocosm study of PAC-modified clay effects on Karenia brevis cells and toxins, chemical dynamics, and benthic invertebrate physiology. Harmful Algae (2024).
2. Influence of Algal Organic Matter on Algal Removal Efficiency by Flocculation of Modified Clay. Journal of Marine Science and Engineering (2023).
3. Current environmental status of the oyster farms on Lake Kamo in Japan; viral control of the harmful bloom of Heterocapsa circularisquama. PeerJ (2023).