PLANKTON 53 



masses of dead algae decreases the toxicity, and that boiling the con- 

 taminated water does not reduce its toxicity. He thought that Microcystis 

 contains two active principles : a potent f ucoin-type hepato-neurotoxin, and 

 a fluorescent photosensitizing pigment, phycocyan. Wheeler, Lackey, and 

 Schott 273 determined that Microcystis is less poisonous when fresh than 

 when frozen or dried. They found the toxin dialyzable, soluble in alcohol, 

 and able to withstand autoclaving in neutral solution. It also survives, 

 unfortunately, the laboratory equivalent of a water purification process — 

 alum coagulation, chlorination, and filtration. It is adsorbable on carbon, 

 but only when this is used in comparatively large amounts. According to 

 McLeod and Bondar, 262 in a Manitoba outbreak associated chiefly with 

 Aphanizomenon (and some Microcystis and Anabaena), the toxic material 

 was in the plants and not in the water. They found the toxin stable 

 in the plant, not destroyed by air drying at 37 °C, by freezing, or by 

 ultraviolet irradiation. Shelubsky 257 claimed in 1951 that the Microcystis 

 toxin is alkali-labile. In contrast with other investigators, Louw 263 has 

 reported isolation of two alkaloids from Microcystis. The first is an in- 

 active one with a probable formula of C 10 H 19 NO 2 . The other, without 

 stated molecular structure, was isolated as a picrate with a melting point 

 of 165 °C. It is supposedly the active hepatotoxin, and it has been effective 

 in experimental rats. Somewhat similar findings with marine algae from 

 the South Pacific have recently been described by Habekost, 274 who iso- 

 lated substances toxic to mice. 



c. Human Intoxications 



Algal poisoning has not been limited to animals. During the past 25 

 years, phytoplankton has also been incriminated in human reactions. These 

 have presented as three general clinical pictures: dysenterial disorders, 

 systemic allergic reactions, and local allergic eruptions. Table VIII sum- 

 marizes the reported human cases. 275 * 281 (Poisonings from ingestion of 

 plankton-nourished fish will be discussed separately later.) 



The epidemic intestinal disorders of the early 1930's involved many 

 thousands of people, in areas as widely separated as the National Parks 

 in the Northwestern United States 275 and Charleston, West Virginia. 276 

 Symptomatology consisted of nausea, vomiting, diarrhea, and sometimes 

 abdominal pain. It was self -limiting and usually resolved in a few days. 

 These outbreaks were of no known specific etiology, but, significantly 

 enough, were always concomitant with the presence of extensive algal 

 blooms in the local water supply. Doubtless many other similar outbreaks 

 have been neither studied nor reported. 



