Sungai Bancaran merupakan sungai yang berada di Kabupaten Bangkalan, merupakanperairan yang banyak terdapat aktivitas manusia dan menjadi perairan yang sangat aktif. Kondisi inimempengaruhi kesuburan perairan, khususnya klorofil-a. Konsentrasi klorofil-a di perairan dipengaruhikonsentrasi nutrien dan intensitas cahaya matahari. Penelitian ini bertujuan untuk mengetahuikonsentrasi nutrien, khususnya nitrat dan fosfat, dan pengaruhnya terhadap konsentrasi klorofil-a serta beban masuk nutrien tiap ton/hari di sungai Bancaran. Penelitian dilaksanakan pada bulan Desember 2019 – Januari 2020 di Sungai Bancaran, Kabupaten Bangkalan. Metode yang digunakan adalah metode deskriptif dengan teknik purposive sampling. Stasiun penelitian dibagi 6 stasiun dengan ulangan 3 kali dengan pengambilan sampel air dan kualitas air secara insitu pada pagi hari. Hasil analisis parameter fisika kimia air selama penelitian diperoleh temperatur air (27,97-29,73°C), pH (6,71-7,12), salinitas (1-5 ppt), oksigen terlarut (4,83-6,32mg/l), kecerahan (40,39-81,06cm), nitrat (1,805–1,937 mg/l), fosfat (0,270–0367mg/l). Klorofil-a (0,249–0,377 mg/m3), beban masuk nitrat (0,099-0,247ton/hari), dan beban masuk fosfat (0,019-0,038 ton/hari). Nilai koefisien korelasi (r) nitrat terhadap klorofil-a (0,075 - 0,964) dan fosfat terhadap klorofil-a (0,037 - 0,941).

Bancaran River is a river located in Bangkalan Regency, a water that has a lot of human activity and becomes very active waters. These conditions affect the fertility of the waters, especially chlorophyll-a. The chlorophyll-a concentration in the waters is influenced by the concentration of nutrients and the intensity of sunlight. This study aims to determine the concentration of nutrients, especially nitrates and phosphates, and their effects on the concentration of chlorophyll-a and nutrient entry load per ton / day in the Bancaran river. The study was conducted in December 2019 - January 2020 in the Bancaran River, Bangkalan Regency. The method used is descriptive method with purposive sampling technique. The research station was divided into 6 stations with replications 3 times with water sampling and water quality in situ in the morning. The results of the analysis of the physical chemical parameters of water during the study obtained water temperature (27.97-29.73 ° C), pH (6.71-7.12), salinity (1-5 ppt), dissolved oxygen (4.83-6 , 32mg / l), brightness (40.39-81.06cm), nitrate (1,805-1,937 mg/l), phosphate (0.270-0367 mg/l). Chlorophyll-a (0,249-0,377 mg/m3), nitrate intake load (0.099-0.274 tons/day), and phosphate entry load (0.019-0.038 tons/day). Correlation coefficient (r) nitrate to chlorophyll-a (0.075 - 0.964) and phosphate to chlorophyll-a (0.037 - 0.941).