While the most common HAB poisoning syndromes have been well described and researched, there is a large group of “emerging toxins” which represent a significant gap in our knowledge about HABs. This group includes newly discovered toxins, as well as phytoplankton-produced toxins that have not yet been linked to human illness. A lack of comprehensive data makes it difficult to fully understand the impacts of these toxins, and many of them are currently unregulated. More research is needed in order to characterize these compounds and prevent them from causing harm. Examples of emerging toxins include:

Spirolides:

These cyclic imine toxins are produced by the dinoflagellates Alexandrium ostenfeldii and A. peruvianum. While these organisms also produce saxitoxin, the compound that causes paralytic shellfish poisoning, it is important to note that spirolides represent a distinct class of toxins with completely separate effects. Spirolides were first reported in Nova Scotia, isolated from scallops and mussels at aquaculture sites, but have since been shown to have a worldwide distribution. Areas affected include the Mediterranean Sea, Chile, New Zealand and the Baltic Sea. No adverse symptoms have yet been reported in humans, but spirolides have been shown to cause neurotoxic symptoms and death in mice. This group of toxins is currently unregulated.

Yessotoxins:

While similar in chemical structure to the toxin that causes ciguatera poisoning, yessotoxin has not been shown to cause human illness. It is produced by the dinoflagellates Lingulodinium reticulatum, L. polyedrum, Protoceratium reticulatum, Gonyaulax spinifera, and was first isolated in 1986 from a Japanese scallop. These organisms have been linked to shellfish dieoffs, but no direct effect of yessotoxin has been established. Yessotoxins have been found around the world, and often co-occur with diarrhetic shellfish toxins.

Pectenotoxins:

Produced by the dinoflagellate Dinophysis, this toxin was originally grouped with diarrhetic shellfish poisoning (DSP) toxins. However, pectenotoxins are distinctly different from okadaic acid and are not the cause of diarrhetic shellfish poisoning symptoms. Pectenotoxins have been demonstrated to be toxic by injection in mice, but oral toxicity is comparatively low. They were first isolated from a Japanese scallop, but is present in many shellfish. Shellfish can metabolize pectenoxins into less toxic forms.

Palytoxins:

These highly toxic compounds were first identified in soft corals, but analogs are produced by members of the tropical dinoflagellate genus Ostreopsis. Palytoxins can accumulate in shellfish and fish that consume Ostreopsis, and these contaminated seafoods causes sickness in humans. Additionally, palytoxins can become airborne during Ostreopsis bloom events, leading to inhalation and exposure during marine recreational activities. While this toxin is being actively researched, there is currently no regulatory framework for palytoxin testing and assessment of public health risk.

Toxin	Causative Organism	Exposure Routes	Affected Areas
Spirolides	Alexandrium ostenfeldii A. peruvianum	Consumption of contaminated shellfish	Mediterranean Sea, Baltic Sea, Chile, New Zealand, Gulf of Maine, Atlantic Canada
Yessotoxins	Lingulodinium reticulatum L. polyedrum Protoceratium reticulatum Gonyaulax spinifera	Consumption of contaminated shellfish	Europe, Russia, New Zealand, Chile, North America
Pectenotoxins	Dinophysis	Consumption of contaminated shellfish	Global distribution, Dinophysis blooms common in North America
Palytoxins	Ostreopsis	Consumption of contaminated fish and shellfish; inhalation of aerosolized particles	Circumptropical distribution