Determining lake metabolizm using diel oxygen technique: A case study of Lake Abant

Recently, diel oxygen method has been intensively used to estimate gross primary production (GPP), net ecosystem production (NEP), and ecosystem respiration (R) from lakes, rivers, and lagoons. This master thesis (1) estimated GPP, NEP, and R of Lake Abant using diel oxygen technique; and (2) built statistical model for the prediction of temporal changes in GPP, NEP, and R. To estimate lake metabolism components using diel oxygen technique, dissolved oxygen concentration (DO, mg L-1), saturated dissolved oxygen value (O2saturated, %), and water temperature (Tw, oC) were continuously measured with YSI-brand water quality monitoring probes installed in situ. To monitor meteorological variables such as solar radiation (SR, W m-2) and wind speed (WS, m s-1) used in the metabolism estimates, T107 T-brand meteorological station was set up by the lake. Measurements were started in 2012 and ended in 2014. Measurements were carried out between the months of June to November. To estimate the components of lake metabolism, nighttime and daytime R values were assumed to be equal. Considering mean annual lake metabolism components as the reference, Lake Abant was found to be of a net heterotrophic character (GPP/R < 1 and NEP < 0) for 2012, 2013 and 2014. Also, GPP and R were modelled as a function of time on a monthly basis. In the statistical modelling, monthly GPP and R averages (obtained from all the stations) were used to construct a general empirical model for the entire lake.