<![CDATA[ABSTRACTPeriphyton is one of microorganisms that serve as primary producer in the aquatic environment. Research aims to determine the chlorophyll-ɑ concentration of periphyton attached in plastic substrate has been carried out in April-May 2018 in the Sail River. There were three sampling stations, namely S1 (in the upstream), S2 (in the middle) and S3 (in the downstream). Samplings were conducted once/week for a 3 weeks period. The periphyton samples were brushed from the plastic substrates (8 x 6) cm2. Water quality parameters measured were water current, temperature, transparency, pH, dissolved oxygen, free carbon dioxide, nitrate, and phosphate. Results shown that chlorophyll-ɑ concentration of peripyhton in the plastic substrate in the S1 was 11.29 μg/cm², in S2 was 14.52 μg/cm²and in S3 there was 26.21 μg/cm². The water quality parameters were as follows: water current 0.07-0.69 m/s, transparency 6.03-7.67 cm, temperature 29-30 0C, dissolved oxygen 4.8-5.7 mg/L, free carbon dioxide 13.6-14.6 mg/L, nitrate 0.29-0.38 mg/L, phosphate 0.34-0.54 mg/L. The chlorophyll-ɑ concentration indicate that the trophic status of the Sail River was eutrophic. The water quality is good and it may be able to support the life of aquatic organisms. Keywords: Lotic, sessile organism, trophic state, water quality]]>
