FAQ — Taxonomic Reference List of Harmful Microalgae

1. What is the Taxonomic Reference List of Harmful Microalgae?

The Taxonomic Reference List of Harmful Microalgae is an authoritative catalogue of microalgal taxa known or suspected to cause harmful effects in aquatic organisms or humans. It is curated under the IOC-UNESCO Task Team on Algal Taxonomy and hosted on the World Register of Marine Species (WoRMS).

2. How is the Taxonomic reference list organised?

The main list is arranged into separate fact sheets, one for each species known to produce toxic substances that cause harm to humans or marine fauna. Fact sheets are searchable by species name or found under headers that correspond to different taxonomic groups.

Each entry includes:

• Valid scientific name and synonyms,
• Documented harmful or toxic effects,
• Key peer-reviewed references,
• Taxonomic notes, nomenclatural history, and WoRMS integration
• Images and identification tips
• References to validated DNA sequences that can be used as taxonomic marker

In a separate section of this website, under the header “Harmful non-toxic”, a list of species that cause harm to marine fauna unrelated to toxin production, e.g., through anoxia related to biomass decay, mucilage, or morphology (e.g. spines) — potentially representing a large number of species — is provided. This second list is accompanied by references or database entries (HAEDAT) providing evidence of the harmful effects of the species included.

3. Why was the Taxonomic Reference List of Harmful Microalgae created?

It was established to provide:

• Stable and authoritative taxonomy for harmful microalgae
• Clarification of names affected by reclassification
• A reference for research, monitoring programmes, and policymakers
• A curated resource linking taxonomy with documented harmful and toxic effects.

4. What is a toxin?

In the context of the list, a toxin is any harmful substance produced naturally by a microalgal species. Microalgal toxins can interfere with biological processes, causing illness or death in marine vertebrates and invertebrates, humans and at times other terrestrial organisms. Microalgal toxins include large and complex poisonous molecules (e.g., palytoxins), smaller molecules, (E.g. domoic acid), different types of lysins, Reactive Oxygen Species (ROS) and Polyunsaturated Fatty Acids (PUFA).

Substances toxic to marine fauna are released in the water and generally are not toxic to humans. Substances causing harm to humans can accumulate in the trophic web and make sea-food toxic, or act directly damaging skin lungs and body mucous membranes. They can also damage marine animals ingesting them.

5. How is toxicity evaluated for the inclusion of a taxon in the Taxonomic Reference List of Harmful Microalgae?

Toxicity evidence must be robust, replicable, and associated with correctly identified strains. Editors evaluate:

• Assay reliability: chemical confirmation (LC-MS/MS, NMR) is prioritised; bioassays alone may be insufficient for inclusion.
• Taxonomic certainty: toxicity must be demonstrated in well-identified or cultured strains; unclear identifications are excluded.
• Reproducibility: multiple studies strengthen confidence; isolated anecdotal reports are not accepted.
• Toxin characterisation: identification of toxin families (e.g. saxitoxins, azaspiracids, pinnatoxins).
• Ecological/public health connection: documented shellfish toxicity, fish kills, or human poisonings attributed to a confirmed species.

Historical, ambiguous, or poorly controlled toxicity reports are not used for inclusion.

7. Who maintains the Taxonomic Reference List of Harmful Microalgae?

The List is maintained by the IOC-UNESCO Task Team on Algal Taxonomy, an international editorial board of specialists in different microalgal groups (e.g., dinoflagellates, diatoms, cyanobacteria).

8. How do I cite the Taxonomic Reference List of Harmful Microalgae?

Usage of data from the IOC-UNESCO Taxonomic Reference List of Harmful Microalgae in scientific publications should be acknowledged by citing as follows:

Lundholm, N.; Bernard, C.; Churro, C.; Escalera, L.; Hoppenrath, M.; Iwataki, M.; Larsen, J.; Mertens, K.; Murray, S.; Probert, I.; Salas, R.; Tillmann, U.; Zingone, A. (Eds) (2009 onwards). IOC-UNESCO Taxonomic Reference List of Harmful Microalgae. Accessed at https://www.marinespecies.org/hab on 2025-11-20. doi:10.14284/362

Individual pages are individually authored and dated and can be cited separately: the proper citation is provided at the bottom of each page.

If the data from the IOC-UNESCO Taxonomic Reference List of Harmful Microalgae constitute a substantial proportion of the records used in analyses, the chief editor(s) of the database should be contacted. There may be additional data which may prove valuable to such analyses.

9. How does the Taxonomic Reference List of Harmful Microalgae relate to AlgaeBase and WoRMS?

The Taxonomic Reference List of Harmful Microalgae aligns its nomenclature with the current taxonomic status adopted in the World Register of Marine Species (WoRMS). WoRMS serves as the primary taxonomic backbone and, in turn, relies on established specialist databases:

• For most algal groups, WoRMS follows AlgaeBase as the authoritative taxonomic reference.
• For diatoms, WoRMS follows DiatomBase.

Accordingly, names used in the Taxonomic Reference List of Harmful Microalgae match their accepted status in WoRMS at the time of updating. This ensures consistency with internationally recognised taxonomic standards, while maintaining a focused scope on harmful and toxin-producing microalgae.

10. How often is the Taxonomic Reference List of Harmful Microalgae updated?

The Taxonomic Reference List of Harmful Microalgae is updated continuously as new taxonomic revisions, toxicological data, and ecological findings become available. Each taxon page includes a revision log.

11. Does the Taxonomic Reference List of Harmful Microalgae include harmful but non-toxic species?

Yes — species causing damage through biomass, mucilage production, mechanical effects, or oxygen depletion may be included if the harmful impact is well documented.

12. What are “greylist” species?

Greylist species are taxa that were previously included in the main list but subsequently removed because of uncertain or insufficiently supported toxicity. They are maintained in the Grey list of the Taxonomic Reference List of Harmful Microalgae to allow to document their removal from the main list and flag the need for further research.

13. Is the Taxonomic Reference List of Harmful Microalgae limited to marine species?

The List focuses on marine and brackish taxa but includes selected freshwater or euryhaline species—particularly among cyanobacteria—that can occur in marine environments.

14. How does the Taxonomic Reference List of Harmful Microalgae interact with PR2 and GenBank?

PR2 (Protist Ribosomal Reference Database)

• PR2 offers curated rRNA sequence taxonomy (18S, 28S).
• The Taxonomic Reference List of Harmful Microalgae uses PR2 as a molecular reference for phylogenetic placement, but PR2’s taxonomy does not dictate the Taxonomic Reference List of Harmful Microalgae nomenclature.
• The Taxonomic Reference List of Harmful Microalgae relies on classical taxonomy and peer-reviewed revisions.

GenBank

• GenBank includes many sequences for harmful microalgae but also contains misidentified or unvouchered entries.
• Editors use GenBank critically, prioritising sequences:
  • from authenticated cultures,
  • associated with type or reference strains,
  • used in taxonomic studies.

GenBank data do not define or validate taxonomy within the Taxonomic Reference List of Harmful Microalgae.

15. How can I suggest changes or propose additions?

Proposed changes, corrections, and supporting evidence can be sent to hab@marinespecies.org.

Clear documentation (references, strain information, toxicological data) greatly improves review efficiency.

16. Is the Taxonomic Reference List of Harmful Microalgae exhaustive?

The Taxonomic Reference List of Harmful Microalgae focuses specifically on taxa with documented harmfulness or toxicological relevance.
The aim is not to list all bloom-forming microalgae, but to maintain a curated resource centred on harmful impacts.

17. Can the Taxonomic Reference List of Harmful Microalgae be used in monitoring or public health contexts?

Yes — the Taxonomic Reference List of Harmful Microalgae is widely used by monitoring agencies and researchers.

However, considering intraspecific variability in toxin production, it should always be combined with:

• local monitoring data,
• strain-level variability information,
• chemical toxin measurements.

18. How do I obtain a full list of all toxic HAB species?

You can:

1. Connect to: https://www.marinespecies.org/hab/index
2. Click on the Advanced Search icon
3. Select the status (accepted if you want to exclude synonyms)
4. Select the taxonomic rank (species)
5. Select belongs to (for ex. cyanobacteria, if you want a list of one or few groups only)
6. Select HAB in the « context » filter
7. Download the list from the WoRMS “Taxon List” tools, which allow export in CSV or Excel formats.

If you need assistance extracting a custom subset (e.g., toxin class, geographic area), editors can be contacted for guidance.