Kandungan bahan organik merupakan salah satu indikator kesuburan tanah, dimana bahan organik menjadi sumber makanan bagi organisme dan tumbuhan mangrove. Nilai bahan organik dapat dipengaruhi beberapa faktor salah satunya yaitu kerapatan mangrove. Ekosistem mangrove di kelurahan Mamburungan merupakan salah satu hutan konservasi yang didominasi vegetasi mangrove Avicennia sp. dan Sonneratia sp. Penelitian ini bertujuan untuk mengetahui nilai bahan organik pada sedimen, kerapatan mangrove, dan hubungan kerapatan terhadap nilai bahan organik pada sedimen di kawasan konservasi mangrove Kelurahan Mamburungan Kota tarakan. Penelitian dilaksanakan dari bulan Januari-April 2019 dengan menggunakan metode deskrptif kuantitatif. Hasil penelitian menunjukkan bahwa nilai bahan organik tertinggi berdasarkan kedalaman ditemukan pada kedalaman 0 cm (top soil), dan berdasarkan stasiun ditemukan pada stasiun 1, yaitu berkisar antara 12,53% - 17,81% dan termasuk dalam golongan sedang. Kerapatan tertinggi ditemukan pada stasiun 1 jenis mangrove Avicennia sp. yaitu berkisar antara 500 pohon/ha – 1.200 pohon/ha dan termasuk dalam kriteria jarang sampai sedang. Koefisien korelasi sebesar 0,3653 dan menunjukkan korelasi cukup kuat.
Kata Kunci: Bahan organik, Kelurahan Mamburungan, kerapatan mangrove

The content of organic matter is an indicator of soil fertility, organic material becomes a food source for organisms and mangroves. The value of organic matter can be influenced by the density of mangroves. The mangrove ecosystem in the Mamburungan Village is a conservation forest dominated by mangrove Avicennia sp. and Sonneratia sp. This study aims to determine the value or organic matter in sediments, the density of mangrove, and the density relationship to the value of organic matter in sediments in the mangrove conservation of the Mamburungan Village Tarakan City. The study was conducted in January-April 2019 using quantitative descriptive methods. The result showed that the highest value of organic matter based on darkness was found at a depth of 0 cm, and based on the station found at station 1, which ranges from 12,53% - 17,81% and included in the medium class. The highest density was found at station 1 with Avicennia sp. mangrove species which ranged from 500 tress/ha – 1.200 tress/ha and include in the rare criteria. Correlation coefficient of 0,3653 and shows a strong correlation. Keywords: Organic matter, Mamburungan Village, Mangrove Density