0^00 



PM 



DISSOLVED OXYGEN VS. TIME OF DAY IN FRENCH CREEK. 



PENNSYLVANIA. AUGUST 17. 18, 1955 



Figure I 



daytime the lower it is likely to drop below it at 

 night. The record for the Little Miami and Ohio 

 Rivers (Figure 3) seems to substantiate this "rule" 

 when compared with the stabilization pond in Fig- 

 ure 8. For the period shown, the Ohio deviated 

 only slightly from air saturation whereas the Little 

 Miami, with more numerous attached algae and a 

 habitat more favorable for photosynthesis, exhibits 

 a little more vigorous photo synthetic oxygen pro- 

 duction . 



Recently, a six- month record of dissolved 

 oxygen has been obtained for a small polluted 

 stream in England (Gameson and Griffith, 1959) 

 using photographic equipment to record the dial 

 readings from a dropping mercury electrode (Briggs, 

 Dyke, and Knowles , 1959). Data for the six- month 

 average diurnal oxygen curve in Figure 4 were ob- 

 tained in this way. While obviously the daily ir- 

 regularities and extremes have been eliminated, the 

 curve shows the times of day when the maxima and 

 minima might be expected for this stream. About 

 two-thirds of the maxima were found to occur be- 

 tween noon and 6:00 p.m.; 85 per cent of the mini- 

 ma , between 7:45 p.m. and 7:45 a.m. This curve 

 is not unusual; it agrees generally with the much 

 shorter term observations on other waters where the 

 minimum commonly has been noted around 3:00 to 



5:00 a.m. and the maximum around 4:00 or 5:00 

 p.m. 



A number of approaches have been made to 

 detect and evaluate the influence of algal photo- 

 synthesis on oxygen resources in streams . For a 

 given reach of a hypothetical stream, Odum (195 6) 

 has attempted to interrelate existing oxygen con- 

 centration, provision of oxygen by inflowing water, 

 the atmosphere, and photosynthesis with losses 

 through respiration and diffusion (Figure 5) . Three 

 main daily processes are noted to affect the oxygen 

 and carbon dioxide concentrations of water flowing 

 between two established points . These are release 

 of oxygen into the water during daylight through 

 photosynthesis (A in Figure 5) , absorption of dis- 

 solved oxygen by all organisms (B) , and oxygen ex- 

 change between water and air (G) . Interplay of 

 these three processes determines the rate of oxygen 

 change (D) and the resulting oxygen concentration 

 (E) that would appear in a homogeneous medium. 



Toward assessing the effect of large quanti- 

 ties of blue-green algae on oxygen resources in 

 Wisconsin's Lower Fox River, Wisniewski (1958) 

 modified the customary B.O.D. procedure to meas- 

 ure algal respiration and photosynthesis . Results 

 for a sample from one station are shown in Figure 6 . 

 When incubated for five days at a light intensity of 



58 



