DISTRIBUSI FITOPLANKTON BERDASARKAN SISTEM INFORMASI GEOGRAFIS (SIG) DAN STATUS TROFIK PERAIRAN WADUK CIRATA, JAWA BARAT
Abstract
Abstrak: Waduk Cirata memiliki peruntukkan sebagai Pembangkit Listrik Tenaga Air (PLTA), perikanan, dan pariwisata. Saat ini kondisi waduk telah mengalami degradasi. Hal ini disebabkan karena banyaknya unsur hara yang berasal dari limbah domestik, limbah industri, dan keramba jaring apung (KJA) yang masuk ke perairan. Indikasi pencemaran organik ini dapat dideteksi dengan fitoplankton. Tujuan penelitian ini adalah untuk menentukan status trofik Waduk Cirata dan mengetahui distribusi kelimpahan fitoplankton berdasarkan Sistem Informasi Geografis (SIG) serta menentukan jenis fitoplankton yang dapat digunakan sebagai bioindikator pencemaran waduk. Pada penelitian ini pengambilan sampel air dilakukan sebanyak tiga kali setiap dua minggu sekali di tujuh lokasi waduk dan pada kedalaman 0,2 m. Parameter utama yang diukur yaitu klorofil-a, kelimpahan individu fitoplankton, kecerahan, dan total fosfat. Selain itu, penentuan Trophic State Index (TSI) juga dilakukan. Distribusi dari tiap parameter dan TSI divisualisasikan dalam bentuk peta menggunakan interpolasi raster pada software ArcGIS 10.1. Hasil penelitian menunjukkan bahwa sebagian besar area Waduk Cirata telah berada pada kondisi eutrofik dengan kecenderungan hipereutrofik pada area pusat KJA. Konsentrasi klorofil-a diketahui berkisar 2,57 "“ 15,80 µg/l, kelimpahan fitoplankton berkisar 459 "“ 132.085 individu/ml, kecerahan berkisar 0,78 "“ 1,26 m, total fosfat berkisar
2,41 "“ 859,04 µg/l, dan nilai TSI berkisar 46,34 "“ 74,74. Secara umum, spesies fitoplankton yang dominan dan dapat dijadikan sebagai bioindikator pencemaran Waduk Cirata adalah Synedra ulna dari Kelas Bacillariophyceae dan Microsystis sp. dari Kelas Cyanophyceae.
Kata kunci: Waduk Cirata, fitoplankton, status trofik, SIG
Abstract : Cirata Reservoir has many functions, such as generating hydroelectricity, fish farming, and tourism. Nowadays the condition in Cirata Reservoir has become severely degraded due to nutrients from domestic sewage, industrial sewage, and fish cages that enter to the reservoir. The indication of this organic pollution can be detected by phytoplankton. The aims of this research are to determine trophic state in Cirata Reservoir and to know the distribution of phytoplankton abundance based on Geographic Information System (GIS) and also to determine the species of phytoplankton that can be used as pollution bioindicator. In this research, water samples were taken three times every two weeks in seven locations and in 0.2 m water depth. Main parameters such as chlorophyll-a, phytoplankton abundance, clarity, and total phosphate were measured. Trophic State Index (TSI) was also accounted. The distribution from every parameter was visualized as a map using raster interpolation in ArcGIS 10.1. The results show that almost the entire area of Cirata Reservoir is already eutrophic and it is hypereutrophic in the centre of fish cages area. Chlorophyll-a concentration is about 2,57 "“ 15,80 µg/l, phytoplankton abundance is about 459 "“ 132,085 organisms/ml, clarity is about 0,78 "“ 1,26 m, total phosphate concentration is about 2,41 "“ 859,04 µg/l, and TSI value is about 46,34 "“ 74,74. In general, Cirata Reservoir is dominated by Synedra ulna from Class Bacillariophyceae and Microsystis sp. from Class Cyanophyceae, hence it can be used as pollutant bioindicators.
Key words: Cirata Reservoir, phytoplankton, trophic state, GIS
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