Oxygen depletion in lake hypolimnia

The Livingstone and Imboden (1996) model for the oxygen depletion rate in lake hypolimnia was evaluated using field results in thirty-two lakes. The volumetric oxygen consumption rate (JV) was strongly related to lake trophic state, as represented by the growing season mean chlorophyll a (Chl a) and annual mean total phosphorus concentration, and may reach a maximum of 0.23-0.24 g O2 m-3 d-1 in eutrophic lakes. The areal oxygen consumption rate (JA) was not related to trophic state, was lower than the value estimated using the sediment core method, particularly in eutrophic lakes; the mean was 0.0816±0.0150 g O2 m-2 whole sediment d-1. We modified the model and it was used to confirm that the field JA, the average for the hypolimnion for the deoxygenation period, is influenced by JV and the range of sediment area to water volume ratio ((Z), Z is water depth) in the hypolimnion, as well as the oxygen consumption rate in whole sediment (R). It was suggested that this is the reason for the difference between field and sediment core JA values. R in ten lakes varied from 7 to 460 g O2 m-3 whole sediment d-1. Overall, the Livingstone and Imboden model with constant JA and a JV value derived from an empirical relationship with either measure of trophic state was considered to be a suitable condensed model for oxygen depletion in lake hypolimnia.