Abundance diversity of benthic fauna and water qualities in the Chao Phraya river
1999
Tippanan Ngamprayad
Abundance and diversity of benthos were studied from 14 sites of the Chao Phraya River in 8 provinces from January to December 1997. Four benthos phyla were found namely Annelida, Mollusca, Arthropoda and Chordata and they were identified into 46 families. The highest number of benthos families found was 24 from the estuary and the lowest was 5 from Amphur Muang Singhaburi province. The highest density of benthos found was 6,736 per square meter at site 12 of Khet Phrakanong in Bangkok and the lowest was 66 per square meter at site 3 of Amphur Muang Singhaburi province. The average density from all sites was 1,441 per square meter. The dominant group found was Annelida, especially in the family Naididae. The high density of benthos was found in the rainy season and the highest was in September. The highest species diversity index and evenness index were 2.08 and 0.79 at site 4 of Amphur Phranakornsriayuthaya whereas the lowest were 0.12 and 0.05 respectively at site 12 of Khet Phrakanong. These indices showed tendencies to indicate water quality in this study when considered concurrently with some environmental factors. Water qualities were studied in many parameters. BOD values from the upstream, middle and downstream were higher than water quality standard value of the second, the third and the fourth class, respectively, while most parameters were still in the range of water quality standard class 3. The calculated water quality index (WQI) was relatively high because FCB value was not included in the calculation. The indices indicated that the water qualities in the upstream and the middle were very good to fair instead of fair to poor, but the downstream qualities were poor at all sites.
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