Physical and chemical variables were sampled at 8:00 a.m. from 10-cm depth. Samples were collected with a 1-L Van Dorn bottle and transported in refrigerated polyethylene bottles to laboratory. Conductivity, dissolved oxygen (DO), and pH were measured in situ using a multi-probe Horiba U-10. The 5-day biochemical oxygen demand (BOD5) and alkalinity analyses
were done according to the Boyd and Tucker (1992) andMackereth et al. (1978), respectively. Analyseswere
performed immediately after sampling, or samples were properly stored under refrigeration at 4 °C.