RELATIONSHIP OP PI I YTOl'LANKTON TO LIMNOLOGY 



75 



bring about the deatli of fisli tliroii^h the 

 liberation of substances toxic to them dur- 

 ing the decay process. I have some experi- 

 mental data at hand (Prescott 1932) to 

 support this and we have numerous refer- 

 ences in the literature. When highly pro- 

 teinaceous blue-green algae undergo decay, 

 sufficient quantities of hydroxylamine and 

 other derivatives are produced to poison 

 any fish caught in the shallow water of a 

 bav bv masses of decaving alcae. In mv 



boating are all made unpleasant or impos- 

 sible because of nauseating odors and the 

 disagreeable condition of heavily infested 

 water. 



Infrequently our attention is called to the 

 death of cattle, claimed to be due to drink- 

 ing from bodies of water containing dense 

 growths of blue-green species. Until re- 

 cently these cases have not been subjected 

 to much scientific analyses, but the Avork 

 done in Minnesota by Fitch et ul. (1934) 



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tjf 





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f 



Fig. 4. Fish dead on the shore of a lake after the break up of winter ice. .Sufl:\)i-ation, the cause of 

 this wholesale death, was due in part to the growth of blue-green algae wliich, under the circumstances 

 of winter conditions, was excessive. This scene is duplicated in late sunnner when large masses of algae 



decay and bring about the destruction of fish. 



controlled experiments, tanks of water were 

 used. One tank was kept as a control. 

 Varying amounts of decayed blue-green 

 algae were placed in the other tanks. A 

 number of different species of fish in tliese 

 tanks died at intervals (except in the con- 

 trol tank), although necessary oxygen con- 

 tent was maintained. 



The ability of phytoplankton to destroy 

 recreational sites is well known. In tliis 

 respect they are often not onl.y a nuisance 

 but an economic menace. Bathing, fishing, 



establishes that a causal relationship actu- 

 ally exists. Laboratory experiments have 

 shown that Avhile alive certain Myxophyceae 

 species liberate toxic substances (or sub- 

 stance) and that these are capable of killing 

 laboratory animals when the water in which 

 these plants have been growing is injected. 

 Whether or not these substances are also 

 lethal for aquatic aninuils is a question ujion 

 which no research has been done, appar- 

 ently. 



Besides the objectionable effects of phyto- 



