Development of macroinvertebrate-based multimetric index and establishment of biocriteria for river health assessment in Malaysia.

• Ecological quality of Malaysian streams can be assessed using a multimetric index. • Six core metrics were identified to develop a MIBI. • MIBI discriminates the reference and test sites very well. • MIBI's efficiency has been tested in various stream to verify its reliability. Economic and industrial growth in Malaysia has led to various environmental problems, which in turn affected the quality of human life and nature. At present, the management plans, particularly for river rehabilitation, are less effective in addressing issues related to Malaysian rivers. To date, most of the efforts undertaken have focused on evaluating the physicochemical properties of water, whereas biological evaluation determining the health of a river ecosystem is less attended to. Therefore, this study has aimed to develop a multimetric index and biocriteria applicable to the biological assessment of Malaysian streams. Four rivers in the state of Johor have been selected as the sources, each representing different gradients of land use. The reference and impaired sites both have been determined based on various physicochemical, instream features and riparian habitat quality criteria. The resulting candidate metrics have then been evaluated in terms of redundancy, sensitivity and responsiveness to environmental changes, using the stepwise procedures. Integration of six potential metrics across three categories (i.e. taxonomic richness, taxonomic composition, and tolerance and intolerance index) has consequently produced a four-level discriminatory biocriteria for river health assessment: <20% (severely impaired); 20%−55% (moderately impaired); 56%−92% (slightly impaired); and >93% (non-impaired). The re-scored result has revealed that the water quality of Sg Ayer Hitam Besar to be non-impaired, with excellent water quality. Meanwhile, Sg Berasau and Sg Mengkibol have slightly impaired water quality, whereas Sg Melana is moderately impaired with fair to poor water quality. Thus, this multimetric index has strongly differentiated the reference and impaired conditions accordingly, which substantiated the suitability of the discriminatory criteria for Johor stream assessment. Hence, the establishment of macroinvertebrate-based index of biotic integrity (MIBI) and biological criteria may provide indispensable information in managing river ecosystem more effectively. [ABSTRACT FROM AUTHOR]