Biological Survey — Oswego Watershed 141 



June to September, 1927. In Cayuga and Seneca lakes samples 

 were taken at two stations, 1 one near the south end and one to- 

 wards the north end at the following' depths: 0, 5, 10, 15, 20, 25, 

 30, 35, 40, 50 meters and bottom. In Oneida lake samples were 

 taken in only one station 2 at three meter intervals from the surface 

 to the bottom, 15 meter depth. 



The following determinations were made at each of the five 

 stations : 



1. Temperature of the water. 



2. Transparency of the water. 



3. Dissolved oxygen. 



4. Free carbon dioxide. 



5. Total alkalinity of the Avater. 



6. Quantitative determinations of the various kinds of plankton 

 organisms. 



7. Total dry matter, organic matter and ash in the lake water. 



Temperature of the Water. — A series of temperature readings 3 

 was taken each time when plankton samples were taken or when 

 water samples were taken for gas determination. 



The records taken over a period of about six months in Cayuga 

 lake show a rise in the surface temperature from 3.18° 4 Centigrade 

 on April 16 to 19.3° C. on August 26. The temperature at the 

 50 meter depth rose from 3.15° C. on April 16 to 7.9° C. on Sep- 

 tember 14. Near the surface and at the lower depths the decrease 

 in temperature per meter increase in depth was but slight. When 

 a definite thermocline occurred (during August and September) 

 the most rapid drop in temperature was not always at the same 

 depth, although usually this occurred between the 20 and 25 

 meter depths. 



The temperature at the surface of Seneca lake increased from 

 about 12.0° C. to 20.1° C. between June 24 and September 7. 



1 The locations of the stations: 



Cayuga lake. "South station"— near the middle of the lake two miles from 

 the south end. "North station"=about one-half mile off the east shore just 

 south of Stony point about 15 miles from the north end. 



fleneca lake. "South station"=about one-sixth mile off east shore south of 

 Hector falls, two miles from the south end. "North station"=about one mile 

 off the east shore opposite the mouth of Reeder creek, six miles from the north 

 end. 



The samples could not be taken in exactly the same spot each time, but 

 all of the samples were taken within a radius of about 100 meters of a com- 

 mon point represented by the "station." This is why the depth of the bottom 

 varied from about 50 to 80 meters. 



2 Oneidu lake. "Station"=:approxiniately one mile off the north shore op- 

 posite the village of Cleveland. Depth, approximately 15 meters. 



3 All temperatures recorded in the tallies of chemical analysis, Series 111, 

 p. 128 were taken with a Negretti-Zambra deep sea thermometer and re- 

 corded without correction for variations due to difference in the temperature 

 of the mercury column. In the few cases where we made these corrections we 

 found the difference to be very small, usually less than 0.1 of a degree. 



* To change degrees Centrigrade to degrees Fahrenheit multiply bv 9/5 and 

 then add 32} eg. (3,18x9/5) +32^37.7 (degrees Fahr.). 



