Keberadaan distribusi nitrat dan fosfat di perairan dipengaruhi oleh arus dan pasang surut. Studi konsentrasi nitrat dan fosfat dapat memberikan informasi variabilitas konsentrasi nitrat dan fosfat dalam mensuplai nutrien pada budidaya rumput laut. Penelitian ini dimulai dengan penentuan stasiun pengamatan melalui pendekatan teknik purposive sampling dan observasi lapangan pada daerah aliran sungai (DAS) yang bermuara pada pesisir perairan budidaya rumput laut Kota Tarakan. Pengamatan langsung (insitu) yaitu kondisi kualitas nitrat, fosfat. Kondisi kualitas air pendukung pH, suhu dan salinitas perairan. Pengambilan sampel pada saat air pasang dan surut. Analisis data secara deskriptif menggambarkan parameter utama distribusi konsentrasi nitrat dan fosfat Konsentrasi nitrat (NO3) pada kondisi perairan pasang berkisar antara 0,24 - 0,46 mg/L, dan surut 0,48-0,6 mg/L, dan konsentrasi fosfat (PO4) pada kondisi perairan pasang berkisar antara 0,24 - 0,46 mg/L, dan surut 0,48-0,6 mg/L. Nilai konsentrasi nitrat dan fosfat ini masih berada dalam kisaran yang baik. Parameter kualitas air lainnya seperti suhu, salinitas dan pH masih berada dalam kisaran yang optimal.

Kata Kunci: Nitrat, Fosfat, DAS, Rumput Laut

Currents and tides affect how phosphate and nitrate are distributed in waterways Research on phosphate and nitrate concentrations can reveal information on how these concentrations vary when delivering nutrients for the growth of seaweed. The purposive sample technique approach was used to choose observation stations, and field observations were conducted in the river flow area (DAS) that emptied into Tarakan City's seaweed cultivation coast. Direct observation (in situ), specifically the phosphate and nitrate quality conditions. Conditions for water quality that sustained the pH, temperature, and salinity of the water. Sampling was both during low and high tide. The primary characteristics of the distribution of phosphate and nitrate concentrations were described using descriptive data analysis. Phosphate concentrations (PO4) were vary from 0.24 to 0.46 mg/L at low tide and from 0.24 to 0.46 mg/L. during high tide, respectively. Nitrate (NO3) concentrations fell between these two ranges. Temperature, salinity, and pH were still within the ideal range for other water quality factors. In order to give more comprehensive information, it would be preferable to do additional research on data collection in Tarakan City using several sample locations (stations). Keywords: Nitrates, Phosphates, DAS, Seaweed