PKOGKESS IN BIOLOGICAL INQUIRIES, 1932 121 



waters of a lake. That is, it was not known whether changes in tem- 

 porature and hydrostatic pressure due to hauHng a sample to the 

 surface from a (h^ptli of 25 meters, for example, made any difference 

 in the hydroszen-ion concentration of the water. In order to answer 

 this question, a qiiinhydrone outfit with a calomel electrode was 

 constructed so that readings could be taken in situ at the various 

 depths. Results obtained with this instrument showed conclusively 

 that hauling a sample to the surface from a depth of 33 meters for 

 the pH determination did not have any appreciable effect upon the 

 hydrogen-ion concentration, even when the sample contained a con- 

 siderable quantity of free carbon dioxide. 



In order to correlate the work on the penetration of solar energy 

 into lake waters with some of the biological phenomena, observations 

 were made on the photosynthetic activities of some phytoplankton 

 algae and on one of the large aquatic plants. These experiments 

 show clearly that the color of the water has an important bearing on 

 the depth at which photosynthesis can take place. 



A quaUtative and quantative survey of the large aciuatic plants 

 was made on 5 of the smaller lakes during the summer and qualita- 

 tive observations on 11 others. Material was also collected for a 

 study of the ecological anatomy of the plants growing under different 

 soil conditions and this investigation is now in progress. 



Phosphate fertilizer was added to the water of Weber Lake in order 

 to determine whether the phytoplankton crop of this lake could be 

 materiall}^ increased by this means. This experiment demonstrated 

 that the phosphate content of a lake of this size can be greatly 

 increased during a period of 3 or 4 months at a cost of about $15 for 

 phosphate material. 



The plankton crop proved to be a little more than 10 percent 

 larger in 1932 than in 1931; but this small increase can hardly be 

 regarded as significant, especially since some of the other lakes on 

 which regular plankton observations were made, showed larger 

 increases without any phospate treatment whatever. 



Plankton observations were made regularly on the six lakes. The 

 average quantity of organic matter in the centrifuge plankton varied 

 from 85 to 140 milligrams per cubic meter of water on a dry basis. 

 The smallest quantity reported, however, was 50 percent larger than 

 in the previous year. From these figures and from the known areas 

 and volumes, the standing crop of plankton per unit of area in various 

 lakes is computed. 



Approximately 8,000 fish were collected during the summer for the 

 purpose of studying their rate of growth. The ahmentary tracts of 

 2,500 fish were examined for the purpose of determining the quantity 

 and kinds of food eaten. Approximately 30 percent of the specimens 

 contained no food, thus leaving 70 percent for analysis. The great 

 majority of those containing food consisted of the following: Perch, 

 796; rock bass, 508; bluegills, 82; ciscoes, 283; and suckers, 99. The 

 remainder consisted of whitefish and various species of game fish. 



The internal parasites of 1,823 fish and 64 birds were studied 

 during the summer. A small trematode larva was found in the eyes 

 of 96 percent of the perch and 92 percent of the rock bass from 

 Muskellunge Lake and in all of the perch and rock bass from Xebish 

 Lake. Only 20 percent of the perch and 24 percent of the rock bass 

 from Trout Lake harbored flesh parasites, while these trematode 



