Algae Diversity as Water Quality Indicator in the Main Water Sources, Nakhon Si Thammarat

The diversity of algae in the 8 main water sources in Nakhon Si Thammarat including rivers, canals, and water falls was studied in eight districts: Klongcry in Tha Sala District, Pak Panang River in Pak Panang District, Klong Thadee in Lanska District, Klong Yong waterfall in Thungsong District, Klong Tha Pae in Maung District. Loung River in Thung Yai District, Klong Saothong in Ronpibul District and Klong Nok Tha in Phrom Khiri District. The results showed that a total of 35 genera belonging to 60 species of four divisions were found. The genera were mostly found in Division Chrysophyta (58%), followed by Chlorophyta (23%), Euglenophyta (13%), and Cyanophyta (6%). The diversity index (H') ranged between 0.57 and 2.21. The dominant genera in all samples were Navicula spp., Chlorella spp., Euglena spp. and Pinnularia spp. Regarding the use of the dominant algal genera as indicators of water quality by AARL-CMU Score, it was found that the water quality index in Klong Yong waterfall, Thungsong District was 5 that means moderate status with medium nutrients (mesotrophic). The dominant genera were Fragilaria spp., Navicula spp. and Pinnularia spp. The water quality indexes in Klongcry, ThaSala District; Klong Nok Tha, Phrom Khiri District; Loung River, ThungYai District; and Klong Saothong, Ronpibul District were 6.75, 7.25, 7 and 5.8, respectively in average water scores that mean moderate to polluted status with medium to high nutrients (mesotrophic to eutrophic). The dominant genera were Rhizosolenia setigera, Euglena spp., Chlorella spp., Navicula spp., Synedra spp., Scenedesmus spp., Oscillatoria spp., Gomphonema spp., Surirella spp., Pinnularia spp., Fragilaria spp. and Phacus sp. Also, poor water quality (the high nutrient levels) showed in Klong Thadee, Lanska District; Pak Panang River, Pak Panang District; and Klong Klong Tha Pae, Maung District with the average water quality indexes of 7.67, 8.67 and 8.5, respectively. The dominant genera were Anabaena sp., Cruciginella sp., Hantzschia sp., Euglena sp.2., Trachelomonas sp. and Scenedesmus spp.  Moreover, the physical and chemical characteristics of water quality as a whole included the temperature ranging between 27.9-31.2 ºC, the transparency of the water ranging from 0.20 to 1.5 meters, color of the water starting from clear, slightly opaque dark brown to black, a pH between 7.00- 8.14, the dissolved oxygen (DO) between 1.8 to 9.4 mg/L, and microbes using oxygen to decompose organic materials (BOD) was between 0.2 to 7.0 mg/L.