Use of ciliated protozoans in the saprobic evaluation of hydrosystems in an equatorial zone (South region of Cameroon)

Agriculture, which accounts for 70% of water abstractions worldwide, plays a major role in water pollution. Resulting pollution poses risks to aquatic ecosystems and humans. With the aim of evaluating the saprobic state of four hydro systems subject to pollution from intensive rubber cultivation, the present study was carried out within and around the Hevecam rubber plantation in Niete, South Region of Cameroon. The study was done from September 2019 to December 2020 with monthly sampling, physico-chemical water analysis and determination of ciliate diversity and distribution. Water in the study stations was acidic (6.40±0.31CU), with average temperature (25.20±0.56°C) and conductivity of up to 761.8 µs/cm. Conductivity values coupled with phosphates (up to 29.7 mg/L), herbicide residues are indicators of agricultural pollution on water quality. Station N2 showed the greatest ciliate abundance and species richness. The long dry season of 2020 showed the highest diversity and abundance. The saprobic index indicated moderate to high levels of organic pollution (2.16 to 3.67). Water quality was degraded with the impact of the agricultural pollution due to the presence of herbicide and fertilizer residues at stations N2 and N4. High levels of phosphates and nitrates have resulted in an increased organic load reflected in the saprobic indices; indicating average to high organic pollution.