Ciguatera is a fooborne illness poisoning in humans caused by eating marine species whose flesh is contaminated with a toxin known as ciguatoxin, which is present in many microorganisms (particularly the micro-algae Gambierdiscus toxicus) living in tropical waters. Like many naturally and artificially occurring toxins, ciguatoxin bioaccumulates in lower-level organisms, resulting in higher concentration of the toxin at higher levels of the food chain, an example of biomagnification.Predator species near the top of the food chain in tropical waters, such as barracuda, moray eel, parrotfish, grouper, triggerfish, and amberjack, are most likely to cause ciguatera poisoning, although many other species have been found to cause occasional outbreaks of ciguatera. Ciguatoxin is very heat-resistant, so ciguatoxin-laden fish cannot be detoxified by cooking.