Monitoring of water quality using aquatic insects as biological indicators in three streams of Terengganu

Aquatic insects are amongst of the most frequently benthic macroinvertebrates used in freshwater monitoring and assessment worldwide. However, relatively less attention has been paid to include aquatic insects for purposes of health and water quality bioassessment particularly in Malaysia. Here, we investigated the abundance of aquatic insects as well as its relationship with physico-chemical parameters in three streams of Terengganu (i.e. Lata Changkah, Sungai Peres and Sungai Ular) which experienced different levels of human disturbance from September to November 2015. A total of 1,361 individuals from seven orders belonging to 35 families of aquatic insects were identified in the streams. The total abundance was significantly greater in Lata Changkah than in Sungai Ular and Sungai Peres (F=5.146, df=2, p=0.035). The most dominant family of aquatic insects in Lata Changkah and Sungai Peres was Heptageniidae (Order Ephemeroptera), followed by Perlidae (Order Plecoptera), Stenopsychidae and Hydropsychidae (Order Trichoptera). In contrast, Libellulidae (Order Odonata) was the most dominant family found in Sungai Ular. High abundance of intolerant taxa such as Ephemeroptera, Plecoptera and Trichoptera were observed in the least disturbed streams; Lata Changkah and Sungai Peres. Decreasing abundance of intolerant taxa and a high number of the most tolerant taxa (Chironomidae, Diptera) were collected from the most highly disturbed stream, Sungai Ular. Based on physico-chemical parameters and biological indices, Lata Changkah and Sungai Peres were categorized as of “Excellent” to “Good” water quality, while Sungai Ular was classified as “Moderately Good”. Findings from this study provide a useful baseline for appropriate water management using aquatic insects as bioindicators for assessing anthropogenic impacts on streams of Malaysia.