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Abstract. 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.
Key Words: benthic macroivertebrates, biotic index, rapid bioassessment, multimetric index, headwater streams, Thailand.
Introduction. Thailand is a developing country. Thus, the major sources of water pollution are domestic sewage, industrial wastes, and agricultural wastes. The major impact of water pollution is the degradation of water supply sources effecting the aquatic ecosystem and public health (Boonsoong et al 2010; Pollution Control Department 2010). Currently, most of the criteria for national standards of water quality assessment are based on chemical integrity which cannot reflect the response to multiple stressors to aquatic resources. Only coliform bacteria measurement can be considered a surrogate for biological parameters (Pollution Control Department 1997). The biological index is a more accurate approach to assessing multiple and cumulative stressors to surface waters by evaluating the condition of biological communities (Karr & Chu 1999). The development and use of biological assessment approaches to monitoring water quality have been implemented in many countries in the European Union (European Union Water Framework Directive 2000) as well as in the United States (Barbour & Yoder 2000; Barbour et al 2000). Recently, the development of biological assessment approaches such as the...