The potential use of local index of biological integrity for tropical river assessment

Abstract

Economic and industrial growth in this country has led to environmental problems which in turn affect the quality of human life and nature. Particularly, the management plans for river rehabilitation are less effective in addressing issues related to rivers in Malaysia. To date, most of the efforts undertaken focused on evaluating physicochemical properties of water whereas biological evaluation in determining the health of a river ecosystem is given less attention. Therefore, this study aims to integrate assessment tools of physical, chemical and biological approaches by highlighting benthic macroinvertebrates as key indicator. This study was conducted at four rivers in the state of Johor, which represents different gradients of land use, namely Sungai Ayer Hitam Besar, Sungai Berasau, Sungai Mengkibol and Sungai Melana. In-situ and ex-situ monitoring were carried out with ten (10) sampling frequencies for each river, starting from 2010 to 2013. Benthic macroinvertebrates were sampled using rectangular dip-net with frame dimension 0.5 m x 0.3 m based on the United States Environmental Protection Agency Rapid Bioassessment Protocol whilst water samples were analysed according to Standard Methods for the Examination of Water and Wastewater. River habitat assessments were also conducted concurrently with the sampling of benthic macroinvertebrates and water quality whereas, secondary data such as rainfall, land use plans and maps of catchment area were obtained from various agencies. Assessment results varied among study sites. Non-parametric statistical analysis, Spearman correlation coefficients was also conducted to measure the correlation between biological and environmental endpoints, hence the selection of most suitable and effective indices for the development of macroinvertebrate-based multimetrics of Index Biotic Integrity (IBI) and the preliminary establishment of the biocriteria. Integration of six potential metrics within three categories (taxonomic richness, taxonomic composition and tolerance and intolerance index) had produced four-level discriminatory biocriteria for river health assessment. The re-scored result showed that water quality of Sungai Ayer Hitam Besar was in non-impaired condition with excellent water quality. Both Sungai Berasau and Sungai Mengkibol showed slightly impaired water quality, whereas Sungai Melana was moderately impaired with fair to poor water quality. The validation of IBI was conducted using different data thus demonstrated that the establishment of IBI and biological criteria could provide indispensable information in managing river ecosystem more effectively.