The Plankton Algae of the Palisades Interstate Park 127 



Another prime requisite before treating a lake is a knowledge of 

 the specific organism or organisms causing the disturbance. (Figure 

 18 illustrates a method of securing samples of plankton.) This is 

 essential because different algae vary greatly in their ability to with- 

 stand the toxic effects of copper sulphate; the susceptibiUty ranging 

 from Uroglena which is killed by one part of copper sulphate in 

 20,000,000 of water, to Scenedesmus and Kirchneriella which require 

 application of five parts per million for their eradication. The com- 

 pilation of a table showing the copper sulphate requirements for 

 destroying the various organisms represents only an approximation, 

 since the varying factors mentioned above increase or decrease the 

 toxic limits for any particular alga. Tables based upon actual field 

 practice have been compiled by Moore and Kellerman and by Jackson 

 and Kellerman. These, as well as reports on the toxicity point in the 

 individual treatment of lakes, have been used in compiling the follow- 

 ing table. The most recent series of experiments, those of Huff ('16), 

 seem to show that even greater dilutions of copper sulphate will give 

 the desired results, although attention should be called to the fact 

 that he assumes an even distribution of the algicide when studying a 

 lake with a marked thermal stratification. 



The only method of determining the organisms causing the trouble 

 is a microscopical examination of the " bloom," and it is hoped that 

 the illustrations accompanying this report (Plates 3-24) will be of 

 service in determining such algae. Experience has shown that dif- 

 ferent species of the same genus may react differently to the copper 

 sulphate, and whenever possible specific determination should be 

 made. Many of the genera incorporated in the following table are 

 not of immediate concern in the problem of blooming at the Palisades 

 Park, but the reaction of all algae which have been treated with copper 

 sulphate is given for the sake of completeness. 



