Chapter 3 - Marine-Based Toxins and Their Health Risk

Abstract

Marine toxins, which are poisonous when ingested, are a threat to human health. Toxins, such as tetrodotoxin, palytoxin, nodularin, and domoic acid, may be produced in large amounts by marine microorganisms, including phytoplankton (dinoflagellates, cyanobacteria, and diatoms) and bacteria. Algal and bacterial toxins are ingested by various species, such as filter-feeding shellfish, zooplankton, and herbivorous fishes. They are accumulated in those organisms and transferred to higher trophic levels along food chains. Diagnosis is made following apparition of various symptoms (abdominal cramps, vomiting, and gastrointestinal disorders), and a history of eating seafood in the preceding 24h. Tetrodotoxin (TTX) is a potent neurotoxin found in marine species especially puffer fish and other terrestrial animals. TTX binds to voltage gated sodium channels that block the flow of sodium ions through the channels. This could result in respiratory and heart failure and could then lead to death. In addition, consumption of seafood contaminated by toxins results in different seafood poisoning syndromes, including paralytic shellfish poisoning, neurotoxic shellfish poisoning, amnesic shellfish poisoning, diarrheic shellfish poisoning, ciguatera fish poisoning, and azaspiracid shellfish poisoning. These toxins are tasteless, odorless, heat and acid stable. Thus, if seafood products are contaminated, intoxications cannot be eliminated by processing techniques, such as canning; marinating; irradiation; and salting. To prevent seafood poisoning, some steps have to be taken, including extensive controlling of toxins content in seafood and banning of the harvesting when toxic algal bloom go beyond a certain level in marine ecosystems.