The Science Centre and Public Utilities Board have together produced this pocket guide to the freshwater phytoplankton found in Singapore reservoirs. These are present in any sunlit freshwater; microscopic in size they are of great importance as environmental monitors, indicating water change and pollution levels. They are also used to absorb heavy metals, and in sewage conversion. Magnifiers have produced these photographs of some 80 species cyanobacteria, green algae and other groups. With glossary, references, and species index.