抄録
The free water method was applied to outdoor experimental ponds with and without fish using semi continuously measured dissolved oxygen (DO) and pH data for 39 days. The rates of primary production and respiration were determined by subtraction the oxygen and CO2 fluxes due to air-water gas exchange and water inflow and outflow from the rates of change in the masses of DO and dissolved inorganic carbon in the ponds. The calculated DIC fluxes could explain the pond carbon budget./Gross primary production rates normalized to chlorophyll-a, particularly the daily rates, were highly correlated with depth-averaged light intensity./The oxygen consumption rates, i.e. respiration and/or decomposition rates were within the range of reported values./They changed little at night, fluctuated between days and varied with the settling rates of particulate matter./We suggest that the metabolic quotients (MQ) were more affected by nitrogen sources during productive periods and by sediment conditions during respiration dominated periods. Important information on carbon and oxygen cycles and the metabolic characteristics of water bodies can be easily obtained and evaluated with such a method.
