Physicochemical conditions and chlorophyll a standing crop were studied from July 1970 through June 1971 in four commercial catfish ponds at the Arkansas State University Experiment Farm near Walcott, Greene County, Arkansas. Determinations of dissolved oxygen, free carbon dioxide, total alkalinity, temperature, pH, transparency, and chlorophyll a standing crop were made at two-week intervals except during fish harvesting operations. One diurnal measurement of dissolved oxygen, free carbon dioxide, and temperature was conducted 25-26 June 1971. Increased oxygen concentrations coincided with increased chlorophyll α concentrations. Free carbon dioxide and chlorophyll α values varied inversely throughout the study. Diurnal concentrations of free carbon dioxide were greatest between 0300 and 0700 hours. Phenolphthalein and total alkalinity values fluctuated throughout the study period, and could not be correlated with other parameters measured. Thermal stratification occurred during the summer and was more pronounced in the more turbidponds. Diurnal temperature measurements indicated that stratification was diurnal. An inverse relationship was found between carbon dioxide and hydrogen-ion concentrations, and all ponds were essentially alkaline. Transparency was relatively constant before the ponds were drained but increased when the ponds were refilled. Suspended particulate matter contributed significantly to turbidity. Peaks of chlorophyll α concentration were found in summer, early autumn, and late winter
