<![CDATA[Arus pasang surut di muara sungai dapat mempengaruhi penyebaran material organik dan zat hara. Keberadaan material organik dan zat hara di perairan dapat menentukan kualitas suatu perairan. Kandungan material organik dan zat hara dalam jumlah berlebihan dapat menyebabkan terjadinya eutrofikasi pada badan air dan menyebabkan kandungan oksigen di perairan menjadi rendah. Penelitian ini bertujuan untuk melihat sebaran material organik, nitrat dan fosfat oleh pengaruh arus pasang surut. Penelitian dilakukan di muara Sungai Demaan, Jepara. Penentuan konsentrasi material organik dalam contoh air laut menggunakan metode titrasi permanganate, sementara nitrat dan fosfat ditentukan dengan menggunakan metode spektrofometrik. Sebaran material organik, nitrat dan fosfat digambarkan dengan software ArGIS, sedangkan simulasi arus pasang surut menggunakan software SMS. Hasil menunjukkan bahwa konsentrasi material organik dan zat hara lebih tinggi saat surut dibanding saat pasang. Sebaran material organik dan fosfat mengikuti arus pasang surut yaitu mengarah ke utara saat surut dan kembali mengarah ke arah selatan pada saat pasang. Disimpulkan bahwa material organik dan fosfat bersumber dari sungai. Kata kunci : arus pasang surut, material organik, zat hara The distribution of organic matter and nutrients in the estuary can be influenced by tidal current. The presence of organic matter and nutrients can determine the water quality. However, the exceed amount of organic matter and nutrient in the water could lead to eutrofication that caused the depletion of dissolved oxygen. The research was aimed to determine the distribution of organic matter and nutrients (i.e. phophate and nitrate) due to the tidal current in Demaan estuary, Jepara. The titration method with permanganate was used to measure the organic matter concentration in the samples. Meanwhile, the spectrophotometric method was used to measure nitrate and phosphate concentration in the samples. Tidal current was simulated by Surface water Modelling System (SMS) software, and the distribution of organic matter, nitrate and phosphate was plotted using ArGIS software. The result showed that the concentration of organic matter and nutrients is higher at ebb tide than flood tide. The distribution of organic matter and phosphate followed the tidal current, flowing to the north at ebb tide and back to south at flood tide. It is concluded that organic matter and phosphate sourced from the rivers. Keywords : tidal current, organic matter, nutrient]]>
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