Methane Concentration on Three Mangrove Zones in Ngurah Rai Forest Park, Bali

Abstract

Mangrove menjadi salah satu ekosistem lahan basah yang berperan penting dalam menyerap karbon. Namun, secara alami ekosistem mangrove juga mampu mengemisikan gas rumah kaca kedalam atmosfer. Metana merupakan salah satu gas rumah kaca yang berdampak signifikan terhadap perubahan iklim. Penelitian tentang siklus metana telah dilakukan di ekosistem mangrove TAHURA Ngurah Rai Bali. Penelitian ini bertujuan untuk mengukur konsentrasi gas metana pada tiga zona ekosistem mangrove. Metode chamber tertutup digunakan dalam pengambilan sampel gas yang kemudian dianalisis dalam gas kromatografi dengan sensor flame ionization detector (FID). Karakter ekologi mangrove yang terdiri dari parameter struktur komunitas mangrove dan lingkungan diukur dari setiap plot kuadrat pengambilan sampel gas. Hasil penelitian menunjukkan konsentrasi gas metana tertinggi ditemukan pada zona darat dengan rata-rata 3,698 ± 0,986 mg. L-1. Walaupun demikian, konsentrasi gas metana pada dua zona lainnya tidak menunjukkan perbedaan yang signifikan dengan zona darat. Variabilitas konsentrasi gas metana tidak berbeda signifikan dengan kondisi struktur komunitas mangrove yang berbeda antar zona. Penelitian ini hanya menemukan variasi nilai potensial redoks (ORP) yang berhubungan signifikan dengan konsentrasi gas metana. Hasil penelitian mengindikasikan bahwa karakter ekologi mangrove yang cukup seragam di kawasan sehingga, tidak menimbulkan perbedaan yang signifikan pada konsentrasi gas metana antar zona. Namun, parameter kondisi substrat lainnya perlu dilibatkan dalam penelitian berikutnya. Abstract Mangrove is one of the wetland ecosystems that play an important role in carbon sequestration and storage. However, the ecosystem also emits greenhouse gas into the atmosphere naturally. Methane has been considered as a significant effect on global warming. A preliminary study in a part of the carbon cycle was conducted on the mangrove ecosystem in Ngurah Rai Forest Park Bali. This study was aimed to determine methane gas concentration in three different mangrove zones. Gas samples were collected by closed chamber method and they were analyzed using gas chromatography embedded with the flame ionization detector (FID) sensor. Mangrove ecological parameters i.e. community structure and environmental condition were determined on each quadratic plot where gas samples were collected. The result showed that the highest methane concentration was found in the landward zone at 3,698 ± 0,986 mg. L-1. Even though, the methane concentration of the other zones had not significantly different from the landward zone. In addition, the mangrove community structure among the three zones was not different significantly. The oxidation-reduction potential was the only factor that had a significant correlation with methane concentration. Those results indicated that mangrove ecological conditions among zones were similar to each other, hence the variation of methane concentration was not significant. Nevertheless, substrate abiotic characters need to be involved in greenhouse gas studies in the future.

Keywords

• mangrove
• carbon
• methane
• sonneratia alba
• pneumatophore, sediment