Biological Survey — Oswego Watershed 143 



Water Analyses. — Determinations were made of the amount of 

 dissolved oxygen and free carbon dioxide, the total alkalinity and 

 the reaction of the water each time when plankton samples were 

 obtained. The water samples for all these determinations were 

 obtained with a closing water sampler of one liter capacity. 



In general, the results of the analyses* for the four months, 

 June to September, indicate that in Cayuga and Seneca lakes there 

 was no free carbon dioxide in the upper 20-25 meters of water 

 after the last of June. Below this depth about 1-2 parts per 

 million of free carbon dioxide were found in the water during 

 the early part of the summer, but late in August and September 

 this was reduced to about 0.5 p. p.m. Oneida lake showed a greater 

 variation in free carbon dioxide in the water between the surface 

 and the bottom, increasing gradually from 1.5 to 3.7 p. p.m. on 

 June 29, from 1.3 to 2.7 p.p.m. on August 10, and from 2 to 4.4 

 p. p.m. on September 7. On July 13 there was no free carbon diox- 

 ide in the upper 3 meters of water, but it increased from 0.3 to 1.9 

 p.p.m. between 6 and 15 meters. 



The dissolved oxygen in the water of Cayuga and Seneca lakes 

 varied between 6.8 and 12.2 parts per million, the variation in 

 Seneca lake being slightly less than in Cayuga lake. In general, 

 the dissolved oxygen was somewhat less from the surface to about 

 20-25 meters than between the 25 meter depth and the bottom. 

 The dissolved oxygen in Oneida lake was lower, in most cases 

 between 6.5 and 8 p.p.m. However, on September 7 the oxygen 

 between and 3 meters was as low as 5.3 to 5.9 p.p.m. 



The total alkalinity of the water varied from 100 to 107 p.p.m. 

 in Cayuga lake, the water being somewhat less alkaline in the 

 latter part of the summer. No striking or constant difference in 

 alkalinity of the water was noted at the various depths or between 

 the two stations. In Seneca lake the alkalinity ranged between 

 84.3 and 100 p.p.m. ; the lowest was found in June at the south 

 station. Determinations of the water of Oneida lake indicated 

 that the total alkalinity gradually increased between June and 

 September. On June 29 the alkalinity gradually increased from 

 9.7 to 15.6 p.p.m. between the surface and bottom, on September 

 7 from 17.8 to about 30 p.p.m. between the surface and bottom. 



Quantitative Determinations of Plankton Organisms. — In 



Cayuga lake, samples of net plankton and nannoplankton were 

 taken at the north and south stations approximately every two 

 weeks between June 15 and September 15, 1927 ; in Seneca lake 

 samples were taken at the north and south stations once a month 

 from June to September ; in Oneida lake, at intervals of two weeks 

 between June 28 and September 6. From these data the accom- 

 panying charts (1-8) were prepared. 



Charts 1-5 give a summary of the abundance, and vertical and 

 seasonal distributions of the Crustacea, rotifera, protozoa, algae 

 and diatoms obtained in the net plankton of Cayuga, Seneca and 



* See tables of chemical analysis, Series 111, p. 128. 



