Aquatic-insect-based biotic indices to assess water quality in klong pae, Rajjaprabha Dam, Surat Thani province 2008-2009

Abstract

This study was conducted between September 2008 and June 2009 to investigate the aquatic insect diversity and its use as biotic indices for evaluating water quality in Klong Pae, the upstream of Rajjaprabha Dam, Surat Thani Province, Southern Thailand. Shannon Wiener index, Thai Biological Monitoring Working Party (BMWPThai) score, Average Score per Taxon (ASPT), Ephemeroptera, Plecoptera and Trichoptera (EPT) index, EPT ratio and Percentage of Diptera were calculated to compare the water quality. Ninety-four taxa from 96 families belonging to 20 orders in three phyla of macroinvertebrates were collected and identified. Seventy-five taxa from 57 families belonging to 9 orders of Phylum Arthropoda were aquatic insects. The results showed that the Baetidae (Order Ephemeroptera) was the most abundant family of the aquatic insects found every month during the studied period. Comparison of the water quality by using aquatic insects and entire macroinvertebrate groups indicated that the ASPT value of the macroinvertebrates was two times higher than that of the aquatic insects. Other biological indices were not correlated with water quality parameters. It was found that different water quality parameters vary with the climatic seasons. The physical and chemical properties of water of Klong Pae, compared with the standard water quality of Thailand, were acceptable.