Kajian status trofik sebagai dasar strategi penataan lingkungan di Telaga Merdada Kabupaten Banjarnegara Jawa Tengah

KUSUMAWATI, Anindya, Dr. Suwarno Hadisusanto

2010 | Tesis | S2 Ilmu Lingkungan

Telaga Merdada adalah danau kaldera di Dataran Tinggi Dieng. Telah terjadi konversi hutan menjadi lahan pertanian kentang dan sayur-sayuran hingga daerah sempadan danau. Penggunaan pupuk secara intensif pada pertanian tersebut beresiko mengakibatkan pengkayaan nutrien (eutrofikasi) pada perairan Telaga Merdada. Tujuan dalam penelitian ini ialah mempelajari kondisi lingkungan dan status trofik Telaga Merdada, serta merumuskan strategi penataan lingkungan di sekitar Telaga Merdada untuk mengendalikan status trofik. Pelaksanaan penelitian menggunakan metode survei. Pengumpulan data lapangan dilakukan pada tanggal 1-3 Agustus 2009. Sampel dan parameter yang diamati yaitu (a) sampel air danau, yaitu transparansi air (kedalaman secchi), suhu, konsentrasi nutrien (Nitrogen Total, Nitrogen organik, Nitrat, Amonia, Fosfor Total), DO, pH serta klorofil-a; (b) sampel tanah, yaitu permeabilitas, tekstur, struktur, kedalaman solum; (c) sampel sedimen danau, yaitu konsentrasi nutrien (Nitrat, Amonia, Nitrogen Total, Fosfor Total). Lokasi stasiun pengamatan meliputi sisi utara, timur, selatan, barat, dan basin terdalam. Masing-masing stasiun pengamatan dicuplik sampel dengan berbagai jeluk sesuai dengan kedalaman. Penentuan status trofik menggunakan indeks Carlson dan OECD. Status trofik perairan Telaga Merdada berdasarkan kandungan nutrien dan transparansi air menunjukkan bahwa perairan Telaga Merdada tergolong kategori eutrofik-hipertrofik; namun nilai kadar klorofil-a menunjukkan belum diikuti terjadinya blooming algae. Strategi jangka pendek untuk mereduksi nutrien berlebih di Telaga Merdada dapat dilakukan dengan metode aerasi dan pengerukan sedimen. Strategi jangka panjang untuk mengendalikan status trofik Telaga Merdada agar berkelanjutan menggunakan pendekatan abiotik, biotik, dan sosial. Selain itu, perlu dilakukan penataan lingkungan untuk mengendalikan eutrofikasi di Telaga Merdada dengan penataan batas terluar dan sempadan danau sesuai peraturan perundangan yang berlaku serta zonasi pemanfaatan lahan sesuai karakteristik lingkungan.

Telaga Merdada is a caldera lake in Dieng plateau. Large amount of vegetation between land and water is eliminated for agricultural expansions, primarily for potatoes farming. Fertilizer application in potatoes farming on has been intensively used. This excessive activities are exposing freshwater ecosystems in Merdada Lake, which result in eutrophication. The objectives of this research were to study environmental condition of Merdada Lake, determine trophic state, and to propose the environmental management strategies in the region of Merdada Lake to control the trophic state. The samples were collected on 1st –3rd August 2009. Five sampling points within Merdada Lake were collected in various depth. At each sampling points, water transparency, clorophyll-a, DO, pH, temperature, were measured. More over, nutrient dynamics of water and sediment were observed. Trophic state was determined by using Carlson index and OECD. Parameters of soil quality surrounding Merdada Lake were observed, including topography, permeability, texture, structure, and depth of soil column. Trophic state of Merdada Lake according to concentration of nutrient and water transparency shows that Merdada Lake has been in the hypertrophic level, however with respect to concentration of clorophyll-a in water body, Merdada Lake still in oligotrophic level. This results demonstrated that Merdada Lake were in unhealthy condition. High concentration of nutrient in Merdada Lake could lead to algae bloom with respect to increasing of water transparency. The proposed strategy to reduce nutrient in Merdada Lake are by aeration and sediment removal have to be considered. The proposed strategy of environmental management to control eutrophication in long term is to manage the outer basin region and riparian lake by abiotic, biotic and cultural approach. More over, land use planning, such as land use zonation, with respect to lake carrying capacity and principal regulation have to be implemented.

Kata Kunci : Telaga Merdada,Status trofik,Eutrofikasi,Merdada Lake,trophic state,eutrophication