Biotoxin

A biotoxin is a poisonous compound made by a living organism, distinct from a synthetic pollutant. In the marine setting the dominant biotoxins are algal toxins from harmful algal blooms: saxitoxins (paralytic shellfish poisoning), brevetoxins (neurotoxic), domoic acid (amnesic), and okadaic acid (diarrhetic). Toxin-producing genera include Alexandrium, Karenia, Pseudo-nitzschia, and Dinophysis. Filter-feeding shellfish concentrate these toxins, so monitoring programs set regulatory limits, for example 800 micrograms saxitoxin equivalents per kilogram of shellfish flesh, and close harvests when bloom toxins exceed them.