ABSTRACT
Harmful algal blooms (HABs) in a strict sense are completely natural phenomena, which have occurred throughout recorded history. Even non-toxic algal blooms can have devastating impacts, however, when they lead to indiscriminate kills of sh and invertebrates by generating anoxic conditions in sheltered bays. Other algal species, even though non-toxic to humans, can produce exudates (including reactive oxygen species) that damage the delicate gill tissues of sh (raphidophytes Chattonella, Heterosigma, dino agellates Cochlodinium, Karenia, Karlodinium, haptophyte Prymnesium). Whereas wild sh stocks are free to swim away from problem areas, caged sh in intensive aquaculture operations are trapped and thus can suffer devastating mortalities. As a rule, cultured sh will not necessarily be tainted with algal toxins and immediate harvesting of marketable sh before they are killed by algal blooms can sometimes be an option. Of greatest concern to human society, however, are algal species that produce potent neurotoxins that can nd their way through shell sh and sh to human consumers where they evoke a variety of gastrointestinal and neurological illnesses (Table 13.1). One of the rst recorded fatal cases of food poisoning after eating contaminated shell sh happened in 1793, when English surveyor, Captain George Vancouver, and his crew landed in British Columbia (Canada) in an area now known as Poison Cove. He noted that, for local Indian tribes, it was taboo to eat shell sh when the seawater became bioluminescent due to algal blooms of the dino agellate Alexandrium catenella, which we now know to be a producer of paralytic shell sh poisons (PSP). The increase in shell sh farming worldwide is leading to more reports of paralytic, diarrhetic ( rst documented in 1976 in Japan), neurotoxic (reported from the Gulf of Mexico as early as 1844), amnesic shell sh poisoning (ASP, rst identi- ed in 1987 in Canada) or azaspiracid shell sh poisoning ( rst documented in 1995 in Ireland). The English explorer Captain James Cook already suffered from the tropical illness of ciguatera sh poisoning when visiting New Caledonia in 1774. Worldwide, close to 2000 cases of food poisoning from consumption of contaminated sh or shell- sh are reported each year. Some 15% of these cases will prove fatal. If not controlled, the economic damage through the slump in local consumption and exports of seafood products can be considerable (Hallegraeff 1993, Van Dolah 2000).
