Relative abundance, density, and diversity of macrobenthic invertebrates in Batlag and Daranak rivers in Tanay, Rizal

This study assessed the present condition of Batlag and Daranak Rivers using macrobenthic invertebrates as indicators of water quality. Five stations were sampled in May, June and November of 1992 using a one square foot Surber sampler (Mundle, 1971). Physico-chemical factors like river width, depth, velocity of flow, volume of flow, substrate composition, temperature, alkalinity, water hardness, and amount of dissolved oxygen were measured to investigate its effect on the density and diversity of macrobenthic invertebrates. Diversity was investigated using Wilhm and Dorris diversity index (1968).Findings show that density of macrobenthic invertebrates significantly increased from May to June. Insects nymphs and gastropods were found to be the most dominant organisms. Substrate composition was observed to play a vital role in the kind and number of organisms which inhabits the stream ecosystem. The larger the sediments, the greater is the surface area for the attachment of insect nymphs and gastropods. In November, density generally decreased. Diversity indices showed that the area studied was moderately polluted