the erratic and sudden appearances of blooms might 

 be determined mainly by B12 -content. 



Doubtless very many instances of disturb- 

 ances by algae have not been reported in the liter- 

 ature; so, we are ignorant of a true pattern of their 

 distribution over the earth. But it is interesting 

 and somewhat enigmatic that those cases which 

 have been reported do form a pattern . In North 

 America, especially, disturbances involving the 

 death of animals are localized in the midpart of the 

 continent. Almost all instances of cattle deaths 

 have been reported from Michigan, Wisconsin, 

 Iowa, Minnesota, the Dakotas, and south-central 

 Canada. Further, it is from this general region 

 that reports are recurrent. There is another area in 

 Australia where lethal blooms of algae develop, and 

 one in south central Africa . The author is aware of 

 but one report of lethal blooms in Europe (Finland) 

 and none from Asia or South America . Algal blooms 

 occur in many parts of the world, of course, but it 

 is the distribution of toxic effects which invites 

 curiosity. Whatever the distribution of bloom-pro- 

 ducing algae is, we can state, rather tritely to be 

 sure, that waters in scattered parts of the earth 

 have critical ecological factors in common: (high 

 nitrate- and phosphate-content , an abundance of 

 CO2, a high pH and suitable temperatures) . 



It has been mentioned that disturbances at- 

 tributable to algae are both directly and indirectly 

 produced. These effects will be discussed later. 

 By way of explanation, it may be mentioned here 

 that direct effects are those arising from sub- 

 stances given off by certain objectionable algae, 

 or through their physiology wherein nutrients nec- 

 essary for the growth of less offensive forms are 

 taken up; clogging of fish gills because of their 

 concentration in shallow water; producing disa- 

 greeable tastes and odors in drinking water, etc. 

 Indirect effects arise as a result of a chain reaction 

 in modification of ecological conditions leading to 

 oxygen depletion, formation of ptomaines as a re- 

 sult of bacterial decomposition, forming poisons in 

 shellfish eaten by man, birds, etc. 



Whereas most of the disturbances of algae 

 are related directly to their physiology, it may be 

 noted in the instances of cyanophycean trouble- 

 makers especially, that their effects are related to 

 morphology and to their habits. For example, the 

 sticky sheath possessed by blue-green algae makes 

 it possible for plants to adhere to one another, thus 

 forming dense mats . Many blue-green algae, es- 

 pecially the trouble-makers, possess gas vacuoles 

 (pseudo-vacuoles) which permit or force the plants 

 to float high in the water . Because of their tre- 

 mendous numbers, the mat is actually elevated 

 above the water level. Thus, in intense illumina- 

 tion and in warm water layers, where oxygen is 

 low in any case, a decaying blanket forms in which 

 oxygen-consuming bacteria thrive. If the species 

 involved were evenly distributed through the water. 



some of their objectionable direct and indirect ef- 

 fects would not occur. Species of Lyngbya , for 

 example, are sometimes extremely abundant, as 

 are some members of the Volvocales. But these 

 forms do not have the mechanisms for producing 

 sticky scums and for causing serious disturbances. 



One instance of an apparent toxic effect has 

 been noted in a subalpine lake just outside Glacier 

 National Park. This is an unusual condition be- 

 cause all of the lakes in the area are relatively 

 soft and are relatively unproductive of plankton. 

 This particular body of water, about five acres in 

 area, has received during the recent past drainage 

 from a small farm and barnyard; sufficient drainage 

 apparently to raise the nitrogen and phosphorus 

 content so that a bloom of Aphanlzomenon flos- 

 aquae is supported . Each year that this bloom de- 

 velops , mud-puppies (Necturus ) die by the scores 

 and those which are not dead are sluggish and roll 

 about on the bottom . 



Deaths of farm animals have been reported 

 from Iowa, Minnesota, North and South Dakota, 

 Wisconsin, Montana, Bermuda, and elsewhere (as 

 mentioned previously) . The greatest economic loss 

 of cattle has been in central South Africa . Here in 

 the shallow pans and reservoirs in the cattle- 

 grazing country, one species of blue-green algae. 

 Microcystis toxica dominates the phytoplankton, 

 producing 'soupy' blooms. Cattle drinking these 

 waters have died by the thousands . Symptoms in- 

 clude convulsions (similar to strychnine poisoning), 

 paralysis, jaundice, constipation, loss of apetite, 

 falling off in milk production, abortion, and skin 

 sensitization. Cases can be acute, with death oc- 

 curing in a few hours after animals have drunk from 

 Microcystis -infested water, or chronic, wherein 

 death does not occur until after some weeks or 

 months . It is thought that the toxin contains two 

 poisons, one of which is found in phycocyanin . 

 This poison, after damaging the liver, is carried 

 by the blood stream to the surface of the body 

 where, being stimulated by ultra-violet light, it 

 produces tenderness, dryness of the skin, and 

 lesions . The other toxin is said to be a liver- 

 neural type or a fucoin . 



Also from Africa, a serious disease of sheep 

 is reported which has now been referred to a photo- 

 sensitizing toxin. Stewart et al (1950) found that 

 cattle, dead from blue-green algal poisoning in 

 Canada , had experienced lung hemorrhages and 

 liver lesions. As reported by Olson (1951), serious 

 outbreaks of animal deaths occurred in 1948 on 

 Round and Fox Lakes in Minnesota where horses, 

 cattle, hogs, and dogs were killed by drinking 

 water infested with Microcystis aeruginosa (flos - 

 aquae ?) and Anabaena Lemmermannii . 



Poisoning is not confined to mammals, how- 

 ever, for from several localities throughout central 

 North America come authentic reports of deaths 

 among water fowl, pigeons, and even song birds. 



27 



