. The ecology of algae : a symposium held at the Pymatuning Laboratory of Field Biology on June 18 and 19, 1959 . 0800 1200 OUOO 0800 1200 OUOO 0800 1200 AM NOON PM PM MIDNIGHT AM AM NOON 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
. The ecology of algae : a symposium held at the Pymatuning Laboratory of Field Biology on June 18 and 19, 1959 . 0800 1200 OUOO 0800 1200 OUOO 0800 1200 AM NOON PM PM MIDNIGHT AM AM NOON 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 ; 85 per cent of the mini- ma, between 7:45 and 7:45 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 and the maximum around 4:00 or 5:00 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
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