Dinoflagellate toxins are potent natural poisons produced by marine dinoflagellate algae that accumulate in filter-feeding bivalves and in fish, causing several distinct food poisonings when contaminated seafood is eaten, including paralytic, diarrhoetic and neurotoxic shellfish poisoning. They are heat-stable, so cooking does not destroy them. Public health protection depends on phytoplankton monitoring, shellfish flesh testing and closure of harvest areas during blooms, with rapid alerts to the trade. Aquaculture operators in bloom-prone regions build monitoring costs into production planning as a routine expense.