Biogeochemical response to physical forcing in the water column of a warm monomictic lake

Based on microstructure measurements of temperature and horizontal current velocity the physical structure in the water column of Lake Kinneret was characterized as a five layer system consisting of a surface mixed layer, lower epilimnion, metalimnion, upper hypolimnion and benthic boundary layer. Using oxygen and hydrogen sulfide as natural chemical tracers, the time scale of chemical change was identified in relation to advection, mixing and biological processes. Rapid changes due to advection that took place on an hourly time scale were removed by referring the data back to the temperature of the water. Biological activity dominated the hydrochemical changes observed in the meta- and upper hypolimnion. These were expressed by DO depletion rates of 2.0 and 0.4 g m(-2) d(-1), respectively. Vertical and horizontal mixing were shown to occur on a seasonal time scale. Once the chemical stratification process was completed the slow mixing through the benthic boundary layer became the limiting factor for subsequent reactions in the water column.