KUALITAS PERAIRAN SUNGAI MUSI BAGIAN HILIR DITINJAU DARI KARAKTERISTIK FISIKA-KIMIA DAN STRUKTUR KOMUNITAS MAKROZOOBENTHOS

Sungai Musi merupakan sungai besar mengaliri wilayah Sumatera Selatan, Lampung, dan Bengkulu , dan bervariasi dalam pemanfaatannya, khususnya di bagian hilir, didominasi oleh kegiatan industri yang membuang limbahnya ke Sungai Musi. Kajian pengaruh industri terhadap Sungai Musi telah dilakukan, namun sebatas analisis fisik dan kimia lingkungan dan belum mengarah kepada pengaruhnya terhadap organisme air. Organisme air adalah indikator penting perubahan lingkungan karena organisme khususnya organisme dasar (benthos) menyimpan sejarah proses-proses terjadi di perairan. Riset yang bertujuan untuk mengetahui kualitas perairan Sungai Musi bagian hilir ditinjau dari karakteristik fisik dan kimia dan struktur makrozoobenthos telah dilakukan di Sungai Musi, Sumatera Selatan pada bulan Mei dan September 2006. Riset dilakukan bersifat survei lapangan. Delapan stasiun ditentukan di Sungai Musi bagian hilir berdasarkan pada perbedaan mikrohabitat. Stasiun riset masing masing antara lain Sejagung, Pulokerto, Jembatan Ampera, Sebokor, Pulau Burung, Upang, Pulau Payung, dan Sungsang. Pada masing masing stasiun, dilakukan pengambilan contoh air untuk parameter fisika, kimia, dan makrobenthos. Contoh air diambil dari atas perahu motor pada kedalaman 1,0 m dari permukaan air dengan menggunakan kemmerer water sampler. Sebagian contoh dianalisis di lapangan (suhu, pH, dan oksigen terlarut) dan sebagian lagi yaitu jumlah padatan tersesuspensi (total suspended solids), jumlah padatan terlarut (total dissolved solids), jumlah karbon organik (total organic carbon), organik karbon terlarut (dissolved organic carbon), konsumsi oksigen biologi (biochemical oxygen demand), nitrat, dan fosfat dianalisis di laboratorium kimia. Contoh makrozoobenthos diambil pada 10 titik di masing-masing stasiun, dengan menggunakan ekman dredge dengan bukaan mulut 400 cm2. Contoh makrobenthos pada masingmasing titik tersebut disortir dengan menggunakan saringan dan kemudian digabungkan (dikomposit) dan diawetkan dengan formalin 10%. Data kualitas air dianalisis dengan principle component analysis dan kelimpahan makrozoobenthos dianalisis dengan analisis cluster. Kualitas perairan di Sungai Musi bagian hilir dikelompokkan atas 2 yang mengalami tekanan berat yaitu dari Sejagung sampai dengan Pulau Burung dan tekanan ringan yaitu dari Upang sampai dengan Muara Sungai Musi. Kelompok pertama dicirikan oleh nilai konsentrasi total dissolved solids, total organic carbon, dan dissolved organic carbon yang tinggi diiringi dengan kelimpahan makrozoobenhthos yang rendah serta didominasi oleh Tubifex sp. Kelompok ke-2 dari Upang sampai dengan Muara Sungai Musi dicirikan oleh nilai konsentrasi total suspended solids yang tinggi, dengan kelimpahan makrozoobenthos yang tinggi dan didominasi oleh Gammarus. Musi River is a large river , crossing three provinces, South Sumatra, Lampung and Bengkulu, and differeing in types and levels of its resources ultization, particularly at the down stream of Musi River, mostly dominated by industries activities producing a waste which flows to the river. Several studies on the effect of industries on the Musi River have been conducted , however , limmieted on physical dan chemical aspects of the water, not yet to evaluate its effect on aquatic organism. Aquatic organism such macrozoobenthos is important indicator of environmental changes since this organism records the history of processes occurred in the water. Study to assess water quality of the down stream Musi River based on physical, chemical water characteristics and macrozoobenthos community structure was conducted at may and september 2006 in Musi River located in South Sumatera Province of Indonesia. The study used inventory field survey. Eight sampling sites; Sejagung, Pulokerto, Jembatan Ampera, Sebokor, Pulau Burung, Upang, Pulau Payung, and Sungsang were selected based on the microhabitat difference. water sampling for physical and chemical parameters and sediment, and macrozoobenthos were carried in each sampling site. Water sample was collected at a depth of 1.0 m from the water surface by using kemmerer water sampler. Some water quality parameters such as temperature, pH, and dissolved oxygen) were directly analyzed in the field, while the others such as total suspended solids, total dissolved solids, total organic carbon, dissolved organic carbon, biochemical oxygen demand, nitrate, and phosphate were analyzed in laboratory. Macrozoobenthos was collected at ten sampling points in each sampling sites using Ekman Dredge of 400 cm2 mouth opening. Macrozoobenthos from ten sampling points was composited, sorted and preserved with formalin 10%. Water quality parameters were analyzed with principle component analysis while macrozoobenthos abundance was analyzed with cluster. Results revealed that water quality at the down stream Musi River was classified into two groups. The first group was the heavy degraded sites from Sejagung to Pulau Burung, characterized by having high concentration of total dissolved solids, total organic carbon, and dissolved organic carbon, low abundance of macrozoobenthos with Tubifex sp. as the dominant species. The second group was light degraded sites from Upang to the mouth of Musi River, characterized by high concentration of total suspended solids and high macrozoobenthos abundance with Gammarus sp. as the dominant species.