Water quality assessment of the Sinchun stream based on epilithic diatom communities

Water quality was assessed 11 sites on the Sinchun Stream, in the region of Daegu City (South Korea), from May 2007 to March 2008 using Diatom Assemblage Index to Organic Water Pollution (DAlpo) and Trophic Diatom Index (TDI). The reference sites were unaffected by effluent from a closed mine or treated sewage and had, epilithic diatom communities that were dominated by saproxenous taxa such as Achnanthes convergens and Cocconeis placentula var. lineata. The water quality of these sites had DAlpo values ranging between 77.5-93.8 and TDI values between 51.3-67.6, indicating beta-oligosaprobic and mesotrophic environments, respectively. Study sites affected by effluent from the closed mine had epilithic diatom communities that were dominated by acidobiontic diatoms, such as Eunotia exigua and Achnanthidium minutissimum. The water quality of these sites had DAlpo values of 45.9-70.8, indicating beta-mesosaprobic to alpha-oligosaprobic environments, whereas TDI ranged between 1.7-66.9, indicating an oligotrophic to mesotrophic environment. Downstream sites affected by the influx of mine effluent and treated sewage had many species and a high percentage of saprophilous taxa, including Fragilaria construens var. venter and Nitzschia amphibia. The water quality of these regions had DAlpo values ranging between 21.8-33.1 and TDI values between 67.5-76.7, indicating alpha-mesosaprobic and eutrophic environments, respectively.