it Is known that laboratory cultures several days 

 old are not so potent as fresh material or young 

 cultures. 



Bishop, Anet and Gorham (1959) have suc- 

 ceeded in extracting an endotoxin from Microcystis 

 aeruginosa (flos - aquae ?). The toxin was not iso- 

 lated, but a syrup- like dialyzate was obtained and 

 many properties were determined. It was found 

 that the toxin is a non-volatile peptide, that it be- 

 haves as a non-ionic substance in electrophoresis 

 in a pH of 2.2 but is negatively ionic at a pH 

 above neutral . Five fractions were found to be 

 present and only one (peptide No. 2) was proven 

 toxic to laboratory animals. This component also 

 included leucine and one other amino acid residue. 



In addition to their lethal effects, some 

 algae produce other types of pathological condi- 

 tions, in human beings for example. Mention was 

 made of intestinal disorders, epidemic in nature, 

 as reported by Spencer and Tisdale (1 .c .) . Further, 

 it seems clear that allergies, asthmatic conditions, 

 and epidermal irritations result from algal toxins . 

 Many persons experience skin irritations and sting- 

 ing rashes after bathing in algal-infested waters. 

 These symptoms are sometimes ascribed to cer- 

 cariae and accordingly inflamations are regarded 

 as the well-known swimmer's itch. Phycocyanin 

 from Anabaena is one particular irritant . Gioeo - 

 trichia will cause similar irritation when it is in 

 bloom condition . 



Mention was made of the indirect effects 

 produced by dense algal populations . Examples 

 are to be found in fish deaths and in human poi- 

 sonings from eating fish and shellfish. Because 

 blue-green algae especially are high in proteins, 

 when they decompose it follows that proteinaceous 

 by-products are formed, some of which are poison- 

 ous. It has been demonstrated that when algal 

 blooms are dense in shallow water, the decomposi- 

 tion products may be concentrated enough to kill 

 fish. Large scale deaths of fish have been noted 

 in East Okoboji Lake, Iowa during periods of dense 

 Aphanizomenon blooms. Examination of the fish 

 (by specialists) indicated that they had not died 

 from suffocation nor from parasitism. Hence, poi- 

 soning was suspected . A large mass of algae was 

 collected and allowed to decay in vats. A variety 

 of fish, freshly seined from a nearby lake, were 

 placed in two large concrete tanks and the D. O. 

 adjusted and maintained at a safe level by intro- 

 ducing oxygen from oxygen tanks . Then the de- 

 cayed algae were poured into the aquaria , and the 

 behavior of the fish observed. After behaving er- 

 ratic for a time the fish all died within a few hours. 

 Chemical analyses of the decayed algae showed 

 the presence of hydroxylamine in quantities theo- 

 retically sufficient to be lethal, and also 8.5 ppm 

 of H2S . A similar experiment to confirm these ob- 

 servations, and with similar results, was con- 

 ducted by constructing lakeside ponds in which 



fish and decaying algae were placed . Adequate 

 D. O. was maintained by allowing fresh lake water 

 to flow into the ponds periodically . 



Mackenthum et al (1945) likewise experi- 

 mented by placing fish in aquaria with lake water 

 in which Aphanizomenon had occurred and in which 

 a decaying plant mass had developed. Perch and 

 crappies were all dead at the end of a 34-hour 

 period although the oxygen was maintained at 8.3 

 ppm. 



It cannot pass unnoticed that disastrous ef- 

 fects of algal blooms are caused by those species 

 in which pseudovacuoles occur. I suggest that 

 there is more than a casual relationship and that 

 research may show that pathological conditions are 

 caused by substances contained in these vacuoles, 

 possibly a gas . I have never read a discussion of 

 this and apparently pseudo-vacuoles have never 

 been investigated in this connection. 



Another type of indirect effect from algal pop- 

 ulations is experienced when human beings and 

 other animals eat fish or shellfish that have fed 

 upon phytoplankton in which the Pyrrhophyta are 

 abundant ( Gonyaulax , Ceratium , Prorocentrum) . 

 Shellfish, especially, store toxins in their diges- 

 tive tract and liver in quantities sufficient to pro- 

 duce death, or at least to cause serious illness in 

 animals who partake. The toxin appears to have 

 no effect however, on the fish or shellfish. 



Puffers (Tetraodon ) store tetraodontoxin which 

 forms a white, water-soluble powder after extrac- 

 tion. It has a suspected formula of C2gH32N02^g . 

 Like other exotoxins, referred to above, this one 

 is non-alkaloid. It has produced death in 60 per 

 cent of the reported cases of poisoning. Persons 

 who eat moray eel ( Gymnothorax) are poisoned but 

 only 10 per cent of the cases are fatal. It is 

 claimed that more than 400 Japanese soldiers died 

 from eating fish in Micronesia, attributable to con- 

 centrations of Pyrrhophyta toxins . 



Another indirect effect chargeable to algae is 

 that of fish-kills by oxygen depletion. In such in- 

 stances algae supply the basic food for bacteria 

 which actively oxidize masses of dead plants. 

 Dissolved O2 is often reduced to zero (or to an 

 amount too low to be read by usual oxygen tests) . 

 As the oxygen decreases below the threshold nec- 

 essary for them, various groups of organisms are 

 suffocated. In Iowa lakes the sequence of deaths 

 in a necritic cycle appears to be first green algae 

 and Protozoa; yellow-green algae and microcrust- 

 aceans; certain species of fish, including carp and 

 sheepshead; then other and all species of fish; 

 finally chironimid larvae and bottom organisms . In 

 one observed climax in an Iowa lake the oxygen 

 dropped from 4.5 ppm. at midday to zero the fol- 

 lowing morning at 1:00 a.m. Later the same day 

 not a single living organism of any kind could be 

 found in this lake. The lake shore was bordered by 

 a 25-foot zone of carcasses, and the water was a 



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