Diurnal variations of dissolved oxygen concentration in a pilot-scale s high rate algal pond system utilizing water from river nile at Namasagali campus, Busitema University

Abstract

Fluctuation in dissolved oxygen concentration (DO) is one of the major water quality parameters influencing aquaculture production. Low levels of DO in earthen ponds cause stress in cultured fish resulting to poor appetite, growth performance and greater exposure to diseases that subsequently leads in low fish yields. This study aimed to investigate the diurnal variations of DO concentrations in a high rate algal pond (HRAP) system to ascertain the potential use of its effluent in aquaculture production. The specific objectives were to: i) determine the DO concentration of a HRAP system over a 12 hour cycle, iii) to determine the influence of temperature and light on DO concentration and, iii) find out if diurnal variation of DO concentration is within the requirement to support fish culture. The study employed a HRAP system constructed and operated at the Faculty of Natural Resources and Environmental Sciences, Namasagali campus, Busitema University. DO concentration and temperature were measured on-site using a multi-meter probe while light intensity data was obtained from an online meteological site. Data was collected at different time intervals i.e.

6:00 AM, 12:00 NOON and 6:00 PM for three weeks from 23/06/2024 to 17/07/2024. Results revealed that DO concentrations varied significantly during the 12 hour monitoring period. Mean DO concentrations recorded were 5.14±0.20 mg/L, 8.53±0.14 mg/L and 7.14±0.14 mg/L at 6:00 AM, 12:00 NOON and 6:00 PM respectively. Mean DO concentration varied significantly with temperature and light intensity throughout the monitoring period with highest DO levels recorded at midday when temperature and light intensity were at maximum. Meanwhile, despite the diurnal variation in DO, mean DO levels were within the recommended range for culture of the commonly farmed tropical fish species i.e. Oreochromis niloticus and Clarias gariepinus. Results of the present study suggest potential application of HRAP system for use in fish ponds to overcome DO concentration problems and the result improvement in fish health and production.