Keanekaragaman Bakteri Serasah Daun Avicennia marina yang Mengalami Dekomposisi pada berbagai Tingkat Salinitas di Teluk Tapian Nauli

Abstract

The aims of this study were investigated the effect of salinity level on the diversity of bacteria and remaining in the C, N and P during the process of composition of the A. marina leaf litter. The research has been conducted at the mangrove forest of Aek Horsik, Badiri, Central Tapanuli, North Sumatera. The leaf litter were collected using litter traps made of nylon mesh 2 mm pore. The traps were position under the A. marina trees in the mangrove forest. The leaf was collected for two weeks period. Litter bag was filled with 50 g leaf litter and put on the forestís floor in four different salinity level, each salinity level with 24 litter bag. The litter bag was observed each 15 days of decomposition. The results of our investigation indicated that totally 16 species of bacteria were isolated from A. marina leaf litter undergoing the decomposition, including Bacillus (5 spesies), Pseudomonas (2 spesies), Aeromonas (1 species), Listeria (1 species), Kurthia (1 species), Escherechia (1 species), Planococcus (1 species), Micrococcus (2 species), Mycobacterium (1 species) dan Flavobacterium (1 species). The highest amounts of bacteria at 10 - 12 ppt were 1,28 x 109 cfu/, whereas the lowest of bacteria at >30 ppt were 0,35 x 109 cfu/ml. Bacillus subtilis was dominant species during decomposition period. The species diversity indices in the leaf litter decomposition at 0 - 10 ppt were 2.20, at 10 - 20 ppt were 2.38, at 20 - 30 were 2.03 and >30 ppt were 1.78. The frequency of the bacteria species colonization during the decomposition process ranged from 12.5 to 100%. The salinity level were influenced to C, N and P remaining in the leaf litter a long decomposition period. Sampel were analyzed for change in total C, N and P during decomposition period. The highest content of C was found in the leaf litter decomposed at 0 - 10 ppt, while the lowest content of C was found in the leaf litter decomposed at >30 ppt. The highest content of N was found in the leaf litter at 10 - 20 ppt, whereas the lowest content of N was found in the leaf litter decomposed at 20 - 30 ppt. The highest content of P was found in the leaf litter decomposed at > 30 ppt, whereas the lowest content of P was found in the leaf litter at 20 - 30 ppt. The N, P content increased during decomposition period.

Tujuan dari penelitian ini adalah untuk mengetahui pengaruh tingkat salinitas terhadap keanekaragaman bakteri dan kandungan unsur hara C, N dan P pada serasah daun A. marina yang mengalami proses dekomposisi. Penelitian dilakukan di hutan mangrove Aek Horsik, Badiri, Tapanuli Tengah Sumatera Utara. Serasah dikumpulkan menggunakan kantong serasah yang terbuat dari jaring nilon dengan mesh 2 mm. Serasah daun dikumpulkan selama 2 minggu. Kantong serasah diisi dengan 50 gram daun kering dan diletakkan di lantai hutan mangrove pada 4 lokasi yang memiliki tingkat salinitas yang berbeda, setiap tingkat salinitas ditempatkan 24 kantong serasah. Pengamatan dilakukan tiap 15 hari. Hasil penelitian menunjukkan bahwa ada 16 spesies bakteri yang berhasil diisolasi dari serasah daun A. marina yang mengalami proses dekomposisi yaitu Bacillus (5 spesies), Pseudomonas (2 spesies), Aeromonas (1 spesies), Listeria (1 spesies), Kurthia (1 spesies), Escherechia (1 spesies), Planococcus (1 spesies), Micrococcus (2 spesies), Mycobacterium (1 spesies) dan Flavobacterium (1 spesies). Jumlah bakteri yang paling banyak ditemukan pada tingkat salinitas 10 - 20 ppt yaitu 1.28 x 109 cfu/ml, sementara jumlah bakteri paling sedikit ditemukan pada tingkat salinitas >30 ppt yaitu 0.55 x 109 cfu/ml. Bakteri yang mendominasi selama proses dekomposisi adalah Bacillus subtilis. Indeks keanekaragam jenis bakteri pada serasah daun A. marina yang mengalami proses dekomposisi pada tingkat salinitas 0 - 10 ppt adalah 2.20, 10 - 20 ppt adalah 2.38, 20 - 30 ppt adalah 2.03, >30 ppt adalah 1.78. Frekuensi kolonisasi spesies bakteri antara 12.5% sampai 100%. Tingkat salinitas berpengaruh terhadap kandungan unsur hara C, N dan P pada serasah daun yang mengalami proses dekomposisi. Kandungan unsur hara C tertinggi terdapat pada serasah daun yang mengalami proses dekomposisi pada tingkat salinitas 0 - 10 ppt, sedangkan kandungan unsur hara C terendah terdapat pada tingkat salinitas >30 ppt. Kandungan unsur hara N tertinggi pada serasah daun A. marina yang mengalami proses dekomposisi terdapat pada tingkat salinitas 10 - 20 ppt, sedangkan kandungan unsur hara N terendah terdapat pada tingkat salinitas 20 - 30 ppt. Kandungan unsur hara P tertinggi terdapat pada tingkat salinitas >30 ppt sedangkan kandungan unsur hara P terendah terdapat pada tingkat salinitas 20 - 30 ppt. Kandungan unsur hara N dan P mengalami peningkatan selama proses dekomposisi.