Diel variations of certain physico-chemical parameters of water in selected aquatic systems

Abstract

A field study was conducted during the months of October, January, May, and July (1979–80) to examine the diel variations in dissolved O2 (DO), pH, dissolved CO2, bicarbonate and carbonate alkalinity, NH4-N, NO3-N, and PO4-P concentration, and conductivity (EC) of the water in six aquatic systems. Water in hyacinth (Eichhornia crassipes) ponds showed very little or no diel or seasonal variations in DO, pH, dissolved CO2, and bicarbonate alkalinity. Dissolved O2 concentration of the water under floating hyacinth cover was in the range of 0.2–3.0 µg/ml, while dissolved CO2 levels were in the range of 10–35 µg/ml. In the aquatic systems with no floating vegetation, i.e., elodea (Egeria densa) pond, cattail (Typha sp.) pond, control pond (filamentous algae and Chara spp.), and eutrophic lake (algae in Lake Apopka), DO and pH of the water increased during mid-day and decreased during the night. Dissolved O2 levels in these ponds were in the range of 5–20 µg/ml during mid-day and 2–8 µg/ml during the night, while pH of the water was in the range of 8–9.5 during mid-day and decreased to 7–8 during the night. An inverse relationship was observed between bicarbonate and carbonate alkalinity of the water in the aquatic systems with no floating vegetation while no carbonates were detected in the water with floating hyacinth plants. Ammonium N, NO3-N and PO4-P concentration of the water in these aquatic systems showed very little or no diel variations.