Estimation of carbon dioxide flux in shallow lakes in Turkey

Kalvenas, Jennifer
The role of Turkish shallow lakes as a sink or source of carbon from 44 shallow lakes sampled once from 2006 – 2012 over six degrees of latitude is analyzed in terms of spatial resolution. Two of the lakes (Eymir and Mogan) were sampled over the spring, summer, and fall seasons from 2006 – 2010 under dry and wet periods and analyzed for temporal resolution. An equation using pH, specific conductivity, wind speed, temperature, and acid neutralizing capacity (ANC) was used to determine CO2 fluxes (Trolle et al., 2011). The influence of altitude, latitude, and environmental factors, including trophic status, was analyzed. In the 44 lakes, an altitudinal gradient of CO2 flux was observed, with higher fluxes at higher altitudes. Median rates of CO2 emission were in 290 mg C m-2 d-1 in the northern highlands (NH), 352 mg C m-2 d-1 in the southern highlands (SH), -8 mg C m-2 d-1 in the northern lowlands (NL), and -21 mg C m-2 d-1 in the southern lowlands (SL). In Lakes Eymir and Mogan, a seasonal flux of CO2 was observed, with higher emissions of CO2 during summer in Lake Eymir and in spring in Lake Mogan, and less CO2 emissions during fall. CO2 fluxes were found to be strongly negatively correlated with pH for Lakes Eymir (r = -0.87, P<0.001) and Mogan (r = -0.90, P<0.001). A change from dry to wet period was observed, with an average increase of 138 mg C m-2 d-1 in Lake Eymir and 214 mg C m-2 d-1 in Lake Mogan. CO2 flux was correlated with salinity in Lake Eymir (r = -0.44, P<0.05), and with water level in Lake Mogan (r = 0.64, P <0.001), which in turn was correlated with plant volume infested (PVI%) (r = -0.65, P<-0.001). Accordingly, it can be anticipated that the lakes’ production, by macrophytes or phytoplankton, may vary CO2 fluxes by fluctuating the pH of the lake.
Citation Formats
J. Kalvenas, “Estimation of carbon dioxide flux in shallow lakes in Turkey,” M.S. - Master of Science, Middle East Technical University, 2014.