Development Of Malaysian Water Quality Indices Using Aquatic Macroinvertebrates Population Of Pahang River Basin, Pahang, Malaysia

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Date
2016-02
Authors
Wan Abdul Ghani, Wan Mohd Hafezul
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Publisher
Universiti Sains Malaysia
Abstract
In this study, a large macroinvertebrates and water parameters data were collected from fifty Pahang River Basin (PRB) tributaries. Initially, the efficiency of three samplers; D-frame and square nets and Surber sampler, for collections of aquatic macroinvertebrates were tested in three rivers. Low relative variation (RV) of macroinvertebrates collected by square net in two rivers (15% and 19%, respectively) indicated its highest efficiency among the samplers. Although the square net required a longer time to process each sample (18.31 min) it recorded the highest macroinvertebrate diversities (Alphaaverage = 13.5). Consequently, the square net was selected to collect macroinvertebrates for comparison of biotic index performances and the derivation of their tolerance values (TVs). Eleven biotic indices were chosen; Family Biotic Index (FBI), Biological Monitoring Working Party (BMWP), BMWP-Thai, BMWP-Viet, Average Score Per Taxon (ASPT), ASPT-Thai, ASPT-Viet, HKHBios, South African Scoring System version 5 (SASS5), SingScore and EPT Index and their performances were compared. Distribution and abundance of macroinvertebrates and hence the performance of biotic indices were not influenced by Malaysian wet and dry seasons (Mann- Whitney, P>0.05). Among the indices, FBI and all BMWPs tended to classify most of the rivers into better water quality, ASPT-Thai and ASPT-Viet moderately polluted while the SingScore and EPT showed most rivers had been polluted. Using WQI as a reference, it was found that adjusted water quality categories of all biotic indices paralleled the tolerance of macroinvertebrates to pollutants. All BMWP indices and SASS5 were positively influenced by varied levels of DO and pH in dry season and COD in wet season which justified their reliability for water quality assessment. Among these indices, BMWP-Viet was identified as the most suitable due to close similarity of its macroinvertebrate fauna to Malaysian taxa. The TVs of Malaysian aquatic macroinvertebrates were estimated by computing the weighted average of macroinvertebrate abundance that responded towards NH4-N and pH, the most important water parameters in Malaysian rivers (identified through forward selection). The TVs of these two stressors were averaged to finally obtain single TV for each taxon (genus or family). The values ranged from 0 (tolerant) to 10 (sensitive) and named as Malaysian Tolerance Value (MTV). These MTVs were used to derive the Malaysian Biotic Index (MBI) and Malaysian Family Biotic Index (MFBI) by dividing the cumulative sum of products of tolerance value (TV) of each taxon multiplied by its number of individual with the total individuals in the sample. Since the performances of the MBI and MFBI were not statistically different (Mann- Whitney, P>0.05), the cluster analysis was used to assign MFBI scores into 5 water quality classes, very good (> 5.9), good (4.5 – 5.8), moderate (3.8 – 4.4), bad (2.7 – 3.7) and poor (< 2.7) water quality. Their boundaries were separated using box plot analysis. The MFBI scores were positively influenced by DO, and negatively by NH4-N, BOD, TN and Pb, which validated their reliability. Accordingly, the MFBI performed better than BMWP-My (BMWP-My calculated using MTV), BMWP and WQI. Based on the findings of this study, the MFBI was the most suitable index to be adopted in Malaysian river water assessment along with the WQI.
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Keywords
River water quality
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