MEASUREMENT OF OXYGEN PRODUCTION AND DEMAND IN LAKE WATERS

By use of a modern BOD bottle probe, a digital read-out meter, and qua druplicate sampling, oxygen concentrations were routinely measured wit h a precision of +/- 0.02 g DO m(-3) This level of accuracy permitted measurement of Water Oxygen Demand (WOD), Net Production (NP), and Gro ss Production (GP) at all depths in the water column of lakes. Sedimen t Oxygen Demand (SOD) was also measured and found to be small when com pared to the total water column oxygen demand in unstratified water bu t was a significant part of the hypolimnetic oxygen uptake. Measuremen ts of GP were found to correlate closely with primary production value s determined independently by means of the C-14 technique. Significant GP was also found in the hypolimnion of a mesotrophic lake, indicatin g that WOD does not always provide a measure of hypolimnetic oxygen up take; net production does so in this situation. Further, WOD was found to decrease by about 20% per day in incubated samples, revealing that WOD incubations should never exceed one day in duration.