Production and consumption of carbon monoxide in a eutrophic lake

CO concentrations were measured in the water of an eutrophic lake by a technique which allowed the detection of bigger or equal than 0.5 nl CO.liter E-1 of water. In spring, when the lake was aerobic to the bottom, CO distribution was relatively homogeneous with concentrations of 40-130 nl.liter E-1. In summer, CO concentrations ranged between 20 and 615 nl.liter E-1 in the aerobic epilimnion and metalimnion, but reached values of bigger than 8,000 nl.liter E-1 in the anaerobic hypolimnion. CO increased during the morning and decreased during the afternoon in the upper water layers as well as in the dark hypolimnion. Incubation of lake water samples from different depths under daylight conditions resulted in a strong CO production. The light-dependent CO production was stimulated by the high numbers of Oscillatoria rubescence in the metalimnion, but also by material from the lake sediment. Incubation of lake water samples in darkness resulted in CO consumption under both aerobic and an aerobic conditions. (IFU)