ANALISIS TROPHIC STATE INDEX CARLSON AIR MUARA SUNGAI BANJIR KANAL TIMUR, SEMARANG - Khasani, Andro; Afiati, Norma; Sulardiono, Bambang (Departemen Sumberdaya Akuatik,Fakultas Perikanan dan Ilmu Kelautan, Universitas Diponegoro, 2017)
ABSTRAKSungai Banjir Kanal Timur merupakan salah satu sungai besar yang dimiliki Kota Semarang. Sungai ini berfungsi dalam sistem drainase dan pengendalian banjir. Beberapa aliran sungai mengalir ke Sungai Banjir Kanal Timur dan berakhir di muara. Muara merupakan segmen yang akan menampung semua beban yang berasal dari sungai. Oleh karena itu, status trofik perairan di muara, khususnya Sungai Banjir Kanal Timur perlu dievaluasi dalam rangka pengelolaan lingkungan dan pemanfaatan sumberdaya alamnya. Penelitian ini dilaksanakan selama bulan Mei 2016 di muara Sungai Banjir Kanal Timur Semarang. Tujuan penelitian adalah untuk mengetahui kualitas air melalui status kesuburan perairan di muara Sungai Banjir Kanal Timur, berdasarkan metode Trophic State Index (Carlson, 1977) dan metode STORET dalam Kepmen LH No. 115 Tahun 2003 tentang Pedoman Penentuan Status Mutu Air dan PP RI No. 82 Tahun 2001 tentang Pengelolaan Kualitas Air dan Pengendalian Pencemaran Air. Variabel utama yang digunakan pada Analisis TSI Carlson adalah kandungan total N, total P, klorofil-a, dan kecerahan air (angka Secchi disk). Metode penelitian menggunakan metode deskriptif dengan penentuan lokasi sampling bersifat purposive sampling. Hasil yang diperoleh dari analisis TSI (Carlson, 1977) berkisar 53 – 57. Kriteria TSI menunjukkan bahwa TSI TP < TSI SD > TSI CHL dan TSI TP > TSI SD > TSI CHL. Pendugaan interpretasi hubungan tersebut menjelaskan bahwa fosfor membatasi biomasa alga (rasio TN/TP lebih besar dari 33:1), dan nilai TSI Chl yang rendah disebabkan beberapa faktor lain selain fosfor seperti, pemangsaan oleh zooplankton, kandungan nitrogen, dan sebagainya yang sifatnya mengurangi biomasa algae. Di sisi lain, analisis (Indeks STORET) menggunakan Kepmen LH No. 115 Tahun 2003 tentang Pedoman Penentuan Status Mutu Air menghasilkan skor, yaitu -8. Berdasarkan hasil penelitian dapat disimpulkan bahwa kesuburan perairan muara Sungai Banjir Kanal Timur, Semarang menurut TSI (Carlson 1977) berada pada status eutrofik ringan atau (Indeks STORET, Kepmen LH No. 115 / 2003) termasuk kategori perairan tercemar ringan. Kata Kunci : Status Mutu Perairan, Trophic State Index Carlson (1977), Kepmen LH No. 115 Tahun 2003, muara Sungai Banjir Kanal Timur Semarang. ABSTRACTEast Banjir Kanal River is one of the largest river owned by the city of Semarang. The river has a main function as drainage system and flood control of the city. Several streams flowing into the East Banjir Kanal River and end at the estuary. As estuary accommodates all loads from the river, therefore, the trophic status of waters in particular for East Banjir Kanal River needs to be evaluated in the context of environmental management and utilization of natural resources. This work was conducted during May 2016 in the estuary of East Banjir Kanal River. The objective was to determine river water quality using Trophic State Index by Carlson (1977) and the STORET method in the Decree of the Minister of Environment of The Republic of Indonesia (Kepmen LH) No. 115/2003 regarding Guideline for the Determination of Water Quality Status and The Government Regulation of The Republic of Indonesia No 81/2001 regarding Water Quality Management and Water Pollution Control. The main variables used in the analysis of Trophic State Index by Carlson, 1977 are total N, total P, chlorophyll-a and water clarity. Descriptive method is used to determine random sampling points. The average results of all stations analysed by means of Trophic State Index (Carlson, 1977) ranged from 53-57. The interpretation showed that TSI TP < TSI SD > TSI CHL and TSI TP > TSI SD > TSI CHL, these mean that phosphorus limit the biomass of algae (the ratio TN/TP larger than 33:1). Furthermore, lower TSI Chl values in all sampling point were due to several factors other than phosphorus, such as predatory zooplankton, nitrogen which worked to reduce algal biomass. The STORET analysis in the Decree of the Minister of Environment of The Republic of Indonesia (Kepmen LH) No. 115/2003 about Guideline for the Determination of Water Quality Status gives an overall score of minus 8. It is concluded that by applying both methods, the estuary of the East Banjir Kanal, Semarang during the course of the study were on light eutrophic status and categorized as lightly polluted waters. Keywords: Water Quality Status, Trophic State Index Carlson (1977), Decree of the Minister of Environment of The Republic Indonesia (Kepmen LH) No. 115/2003, Estuary of East Banjir Kanal River Semarang.