HABs and Biotoxins: Marine Biotoxins

SEM image Marine Biotoxins

Marine biotoxins, produced by phytoplankton usually during HAB events, are some of the most potent toxins in the world and extremely dangerous. For some toxins, doses at the microgram per kilogram level are more than sufficient to kill. When enough toxin is accumulated in fish or shellfish, small amounts of cooked or raw tissue can kill a human. For example, recorded HAB events have produced enough PSP toxin in mussels that the consumption of one or two small mussels could have killed a normal, healthy adult human. While some toxins are very potent, i.e., requiring only small amounts to produce illness or death, other less potent toxins may accumulate to such high levels that they still can cause harm. For example, the total dose of domoic acid to produce a minimal toxic effect is fairly high (i.e., tens of milligrams) but it can accumulate in sufficient quantities in shellfish to produce deadly results (ranging from mild stomach distress to permanent brain damage and even death).

The risk of poisoning from consumption of fish or shellfish is serious and of concern to public health authorities in all coastal environments. This is true both in the United States and worldwide. The risk and threat to public health is so great that virtually all countries have instituted some form of risk management plan to deal with marine biotoxins. These "sanitation" plans are difficult to design and implement because the properties of the toxins are only poorly understood, not to mention the origins and responsible alga may also not be known.

Toxins in the Pacific Region

NOAA's region of responsibility in the Pacific encompasses an area that stretches literally from the Image of a warming sign for toxic clams North Pole to south of the equator. Within this region a myriad of toxins occur that range from temperate toxins, such as Paralytic Shellfish Poison or PSP (the syndrome is caused by suite of toxins called the saxitoxins or gonyautoxins) and domoic acid poisoning, to tropical toxins such as ciguatera fish poisoning (the toxin is called ciguatoxin). The properties of these toxins are also quite different, ranging from the "fat soluble" ciguatoxin to the water soluble toxins of domoic acid and PSP.

While these toxins originate from phytoplankton, these algae come from ecological niches that are all very different from each other. In the tropics, ciguatera poisoning is caused essentially by reef dwelling fish and the responsible phytoplankton is a dinoflagellate (Gambierdiscus toxicus) that lives on coral reefs and other surfaces. In temperate waters, the PSP toxins are produced by the dinoflagellate Alexandrium catenella and domoic acid by diatoms in the genus Pseudo-nitzschia. All of these differences (chemical, ecological, and biological) make it difficult to design simple, one stop monitoring techniques for these toxins and poisoning syndromes that would be applicable throughout the region.

To read more about marine biotoxins and methods of detection and analyses, please use the navigation bar to the right.

For more in depth descriptions of the toxin syndromes, we suggest that you might want to look at the extensive monograph by Bruce W. Halstead ("Poisonous and Venomous Marine Animals of the World" (Darwin Press). .