ABSTRACT The study was conducted in August-October 2019. Aims to determine theconcentration of nitrate, phosphate, uniformity index, diversity and index of dominancy,abundance of epipelic diatoms and know the relationship between nitrate,phosphate and epipelic abundance diatoms in the water area of Sungaitohor DesaMeranti of Riau Islands district. The method used in this research is a surveyme…