Development of biotic index based on rapid bioassessment approaches using benthic macroinvertebrates for Chi and Mun headwater streams, northeast Thailand

The objective of present study is to select high performance metrics for developing a multimetrics biotic index to assess headwater stream conditions of the Chi and Mun basins in northeastern Thailand (Khorat Platau (Mekong) ecoregion) by using benthic macroinvertebrates based on rapid bioassessment protocols (RBPs). Multimetric biotic indices were developed by two methods (decrease and continuous methods). Nine statistically valid metrics were selected from 24 candidate metrics. These nine metrics represent taxa richness, community composition, tolerance/intolerance, functional feeding and habit measure and include the number of total taxa, number of EPTC taxa, Margalef index, Beck’s biotic index, Simpson’s index, percent intolerance, number of filterer's taxa, number of scraper taxa, and the number of clinger taxa. The results of the biotic index performance demonstrate that the DRQ1 index score (decrease method) produced slightly higher correlation with total habitat score (r = 0.82, p < 0.001) than did the CAU index score (continuous method, r = 0.81, p < 0.001). A narrative assessment analysis is recommended when using a multimentric index approach and appears to provide a useful assessment of stream conditions in the Chi and Mun basins.