Anthropogenic impacts on the distribution and biodiversity of benthic macroinvertebrates and water quality of the Langat River, Peninsular Malaysia M.Z. Azrina, C.K. Yap à , A. Rahim Ismail, A. Ismail, S.G. Tan Department of Biology, Faculty of Science, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia Received 7 January 2005; received in revised form 28 March 2005; accepted 1 April 2005 Available online 17 June 2005 Abstract A study of the impacts of anthropogenic activities on the distribution and biodiversity of benthic macroinvertebrates and water quality of the Langat River (Peninsular Malaysia) was conducted. Four pristine stations from the upstream and 4 stations at the downstream receiving anthropogenic impacts were selected along the river. For 4 consecutive months (March–June 1999), based on the Malaysian DOE (Malaysia Environmental Quality Report 2000, Department of Environment, Ministry of Science, Technology and Environment Malaysia. Maskha Sdn. Bhd. Kuala Lumpur, 86pp; Malaysia Environmental Quality Report 2001, Department of Environment, Ministry of Science, Technology and the Environment Malaysia) water quality index classes, the upstream stations recorded significantly (Po0:05) higher Biological Monitoring Working Party scores and better water quality indices than those of the downstream. The total number of macrobenthic taxa and their overall richness indices and diversity indices were significantly (Po0:05) higher at the upstream stations (54 taxa) than at the downstream stations (5 taxa). The upstream of the Langat River was dominated by Ephemeroptera and chironomid dipterans while other orders found in small quantities included Trichoptera, Diptera, Plecoptera, Odonata, Ephemeraptera, Coleoptera, and Gastropoda. On the other hand, the downstream of the river was mainly inhabited by the resistant Oligochaeta worms Limnodrilus spp. and Branchiodrilus sp. and Hirudinea in small numbers. The relationships between the physicochemical and the macrobenthic data were investigated by Pearson correlation analysis and multiple stepwise regression analysis. These statistical analyses showed that the richness and diversity indices were generally influenced by the total suspended solids and the conductivity of the river water. This study also highlighted the impacts of anthropogenic land-based activities such as urban runoff on the distribution and species diversity of macrobenthic invertebrates in the downstream of the Langat River. The data obtained in this study supported the use of the bioindicator concept for Malaysian rivers. Some sensitive (Trichopteran caddisflies and Ephemeraptera) and resistant species (Oligochaeta such as Limnodrilus spp.) are identified as potential bioindicators of clean and polluted river ecosystems, respectively, for Malaysian rivers. r 2005 Elsevier Inc. All rights reserved. Keywords: Anthropogenic impacts; Benthic macroinvertebrates; Water quality; Langat river; Peninsular Malaysia 1. Introduction Studies of river macrobenthic invertebrates as biolo- gical monitoring techniques have been widely reported and described in the literature (Cairns and Der Schalie, 1980; Cairns, 1981; Matthews et al., 1982; Herricks and Cairns, 1982; Buikema et al., 1982; Cherry and Cairns, 1982; Ogbeibu and Oribhabor, 2002; Mason and Parr, 2003). This is due to the fauna organisms being found along the river continuum. Most interestingly, fresh- water macroinvertebrate species vary in sensitivity to organic pollution and, thus, their relative abundances have been used to make inferences about pollution loads. In natural pristine rivers, high diversity and ARTICLE IN PRESS 0147-6513/$ - see front matter r 2005 Elsevier Inc. All rights reserved. doi:10.1016/j.ecoenv.2005.04.003 à Corresponding author. Fax: 603 86567454. E-mail addresses: yapckong1973@yahoo.com.sg, yapckong@hotmail.com (C.K. Yap).