Benthic algae as monitors of heavy metals in various polluted rivers by Energy Dispersive X-Ray Spectrometer

Benthic microalgae assemblages were used as monitors of copper (Cu), zinc (Zn), and chromium (Cr) in various polluted rivers of San-Yeh-Kong, in southern Taiwan, and analyzed using Scanning Electron Microscope and Energy Dispersive X-Ray Spectrometer (SEM-EDS). Under SEM-EDS, the benthic algae from seriously polluted rivers (dominant by the cyanobacteria Oscillatoria chalybea, green algae Euglena acus and diatom Nitzschia palea under light microscopes) revealed the elemental compositions of heavy metals such as Cu, Zn, Cr, Ti, and that of Mg, Al, Si, P, S, Cl, K, Ca, and Fe. In contrast, benthic algae from moderately (dominant by diatoms Cymbella turgidula and Gomphonema globiferm) and lightly polluted river (dominant by diatom Diatoma vulgare) didn't have any heavy metal elements. In addition to the algal samples, unfiltered water and bottom mud were also investigated for comparison. Further experiment involving the benthic algae from seriously polluted station revealed that all dominant species could survive on the 1 mL 60 ppm Cu, 1 mL 60 ppm Zn, and 1 mL 60 ppm Cr separately after five days culture. The data of this preliminary study are sufficient to encourage further experimentation into the potential for detecting benthic algae as a bioindicator under SEM-EDS to provide rapid information about water pollution.