Toxic Diatom Dynamics in Marine Ecosystems

Toxic diatoms, particularly those of the genus Pseudo-nitzschia, play a dual role in marine ecosystems as primary producers and as sources of potent neurotoxins such as domoic acid. Under favourable environmental conditions—nutrient enrichment, stratification and temperature shifts—these diatoms can form harmful algal blooms (HABs) that disrupt food webs and pose risks to wildlife and human health. The dynamics of toxic diatom populations are governed by life-cycle transitions, genetic regulation of mating types, and interspecific competition within the phytoplankton community. Recent advances have elucidated the molecular underpinnings of bloom initiation, sexual reproduction and toxin biosynthesis, while long-term monitoring has revealed environmental drivers and seasonal patterns of toxin accumulation in shellfish. Integrative approaches combining microscopy, molecular diagnostics and community-level ‘omics are now shedding light on how environmental change, including coastal eutrophication and climate warming, influences the timing, intensity and toxicity of diatom blooms. Understanding these processes is critical for predicting HAB events, safeguarding aquaculture, and managing coastal resources on a global scale.

Research from Nature Portfolio

One foundational study uncovered the genetic basis of mating-type determination in Pseudo-nitzschia multistriata, identifying a single gene whose expression dictates sexual compatibility. Manipulation of this gene induced sex reversal, highlighting a simple regulatory programme underlying bloom dynamics through sexual reproduction and genetic diversity. Another seminal investigation sequenced the transcriptomes of multiple Pseudo-nitzschia species to compare metabolic pathways and identify candidate genes involved in neurotoxin production. Notably, a nitric oxide synthase gene unique to the toxin-producing species was discovered, suggesting a signalling role for nitric oxide in the regulation of domoic acid synthesis.

Toxic Diatom Dynamics in Marine Ecosystems publication trend

The graph below shows the total number of articles in toxic diatom dynamics in marine ecosystems across all publications each year (not limited to Nature Index journals).

Technical terms

Harmful algal bloom (HAB): A rapid increase in the population of toxin-producing microalgae that can harm marine life and human health.

Pseudo-nitzschia: A genus of marine diatoms, some species of which produce the neurotoxin domoic acid.

Domoic acid: A potent excitatory neurotoxin produced by certain diatoms, responsible for amnesic shellfish poisoning.

Metatranscriptomics: The study of collective RNA transcripts from an environmental sample to assess gene-expression dynamics of microbial communities.

Mating type (MT): A genetically determined classification in diatoms that governs sexual compatibility and reproductive cycles.

References

1. Sexual reproduction during diatom bloom. ISME Communications (2025).
2. Advancing the Taxonomy of the Diatom Pseudo-nitzschia Through an Integrative Study Conducted in the Central and Southeastern Adriatic Sea. Plants (2025).
3. Marine phycotoxin levels in shellfish—14 years of data gathered along the Italian coast. Harmful Algae (2023).
4. MRP3 is a sex determining gene in the diatom Pseudo-nitzschia multistriata. Nature Communications (2018).
5. Transcriptome sequencing of three Pseudo-nitzschia species reveals comparable gene sets and the presence of Nitric Oxide Synthase genes in diatoms. Scientific Reports (2015).