Diurnal and Seasonal Variations of Exchange Rate of Carbon Dioxide across an Air-Lake Water Interface

Abstract

The exchange rate of CO₂ between the atmosphere and Lake Suwa, a eutrophic lake in Nagano Prefecture (Japan), was estimated based on a floating box experiment.
The diurnal variation of the exchange rate of CO₂ indicated that the ratio of photosynthetic rate to respiratory rate including organic matter decomposition is highest at 15 o'clock and lowest at 3 o'clock.
The seasonal variation of the average daily exchange rate of CO₂ indicated that the absorption flux of CO₂ occured during the period from early spring to middle summer and the evolution flux of CO₂ during the period from late summer to late autumn.
The average daily absorption rate of CO₂ on 17-18 July 1973 was estimated at 1.3 CO₂-C g/m²/day, when the water bloom of Microcystis developed.