A Comparison of the macro-invertebrate communities in two Malaysian streams

Abstract

The study aims to characterize the community of macro-invertebrates in rivers of tropical Malaysia. To this end, the composition, abundance, diversity of macro-invertebrate populations and their longitudinal distributional patterns in a pristine (Selai River, a headwater of the Endau-Rompin National Park at south-eastern part of Peninsular Malaysia) and an urban (Langat River - a designated potable water source at an urban area near Kuala Lumpur) streams were compared. The benthic macro-invertebrate populations of both rivers were sampled over two years using visual-hand and kick-net collections at thirteen stations in each location. Selai River has a rich and diverse macro-invertebrate fauna comprising 130 genera in sixty-seven families and twelve orders as compared with that of Langat River which consists of fifty-seven genera in forty-three families and thirteen orders. There are fifteen dominants in Selai River doubling that in Langat River. The former community is dominated by the species of Philopotamidae and Hydropsychidae (caddisflies), Heptageniidae and Baetidae (mayflies) and Euphaeidae (damselfly) while the latter by species of Chironomidae (red-blood worm) and Haplotaxidae (segmented worm). In parallel with such contrasting dominance, the Ephemeroptera-Plecoptera-Trichoptera (EPT) is the richest and abundant assemblage inhabiting the fast-flowing erosional zone and diverse microhabitats available in Selai River while Zygoptera-Anisoptera-Diptera (ZAD) and non-insecta predominate at the slow-flowing depositional zone in Langat River. Taking Selai River as a reference point to make corrections for unequal rates of tolerance and compositional change among the benthic invertebrates, a high index of 2.0 was estimated for the Langat's community loss. The distributions in the two communities show subtle differences. Macro-invertebrate community in Selai River is a natural and complex one as compared with an altered and simplified community in Langat River. Such contrast suggests that the functional organization of benthic organisms along Selai River continuum is still stable while longitudinal change and de-stabilization in the organization of macro-invertebrate community has taken place in the latter river system.

Key words: Benthic macro-invertebrate community, distribution, river gradients, water quality

Journal of Aquatic Sciences Vol.20(1) 2005: 13-26