Modeling and Validating Long-Term Dynamics of Diel Dissolved Oxygen with Particular Reference to pH in a Temperate Shallow Lake (Turkey)

Long-term monitoring of changes in dissolved oxygen (DO) and pH is of great importance to quantifying aquatic ecosystem metabolism, particularly for lakes under the changing global environment. During 173 days, diel DO cycles were measured in situ along with the main driving variables of pH, wind speed (WS), and net solar radiation (Rn) in a temperate shallow lake. Best-fit multiple non-linear regression (MNLR) models of diel DO time series were built and validated on a monthly basis, with R(2) values ranging from 42.4% in September to 95.4% in November for validation. The strong relationship between diel DO and pH (r = 0.6) appeared to be related to the patterns of ecosystem productivity and respiration, and sensitivity of decomposing bacteria to changes in pH. pH-driven lake metabolism appears to have significant implications for diel and seasonal lake metabolism in a changing global environment.