Diurnal Changes of Selected Physico-Chemical Properties of Water and Aquatic Insects in a Seasonal Pond

Abstract

Diurnal changes of selected physico-chemical parameters of water (temperature, dissolved oxygen [DO], conductivity, total dissolved solids [TDS], turbidity and pH) and aquatic insects in a seasonal pond in Aborlan, Palawan were investigated in January 2002. Physico-chemical parameters were measured every hour using digital equipment starting 9 AM until 8 AM the next day. Dip net was used to sample aquatic insects at different times (9 AM, 1 PM, 5 PM, 12 midnight, and 5 AM).

All water parameters measured tended to be higher at daytime than at night. Water temperature ranged from 22.8-31.4°C while DO ranged from 2.4-6.2 mg/L. Water conductivity and TDS, which ranged from 79.1-87.8 μS/cm and 39.5-43.5 mg/L, respectively exhibited the same trend with dimodal peaks at 11 AM and 6 PM. Turbidity irregularly fluctuated ranging from 16.3-31.2 NTU while pH did not vary much ranging from 5.5-6.3. There was a significant linear correlation between water temperature and other measured physico-chemical properties of water.

Most aquatic insect groups showed nocturnal behavior but Libellulidae (dragonfly nymphs) and Corixidae (water boatmen) were constantly collected at different sampling times and most abundant at 9 AM. The physico-chemical properties of the water in the pond were influenced by temperature and most aquatic insects are nocturnal in behavior and seemed affected by the diel water temperature.