No abstract

Seagrass ecosystems in shallow waters, including in highly dense small islands, are vulnerable to anthropogenic activities and may lead to a decreasing in seagrass area and percentage cover. As a result, it will negatively affect climate change mitigation, i.e. a decrease in seagrass carbon stock. This research was conducted to evaluate seagrass carbon stock changes in Barranglompo Island, Spermonde archipelago, in 2001 and 2017. Carbon stock estimation was carried out by collecting seagrass biomass based on the category of a sparse, medium, and dense seagrass coverage (each with 20 replications) and analysing their carbon concentrations. Changes in carbon sequestration were analysed using an estimated approach to the changes in the seagrass bed areas. Landsat and Worldview-2 image analysis were utilized to estimate the area of seagrass beds in 2001 and 2017, respectively. Results showed a decrease in seagrass beds by 9.9 ha, from 66.8 ha in 2001 to 56.9 ha in 2017, or an average of 0.62 ha per year. Based on that, it was estimated that seagrass carbon stocks had declined from 74.19 tons in 2001 to 65.21 tons in 2017 or decreased by an average of 0.75% per year. Anthropogenic activities, such as boat anchors as well as household waste disposal in the seagrass area, are considered having the potential in causing a decrease in seagrass area and the percentage coverage.

Mangroves have numerous ecological functions as well as economical values. In order to achieve successful of mangrove restoration and regain its functions, understanding on the factors affecting the establishment of mangroves are required. This study examined the characteristics of physico-chemical factors from three compartments (sediment, interstitial and seawater) that associated with different mangrove densities in Ampallas, District of Mamuju, West Sulawesi. The Principal Component Analysis and Spearman correlation analysis showed that high densities of adult and seedling mangroves strongly correlated to higher organic contents, dissolved oxygen of interstitial water, seawater salinities and lesser pH of sediments, seawater and interstitial. The reverse conditions applied for the less mangrove densities and control site that had no mangrove. In most cases, there were reciprocal relationships amongst the studied variables.Keywords: chemical-physical factors, density, mangroves.

Ekosistem padang lamun merupakan ekosistem yang umum ditemukan di Kepulauan Spermonde, salah satunya adalah Gusung Bonebatang. Lamun mempunyai kemampuan menyerap karbon untuk proses fotosintesis sehingga berpotensi dalam  mitigasi perubahan iklim.  Penelitian dilakukan pada bulan Agustus 2017 untuk membandingkan penyerapan karbon oleh jenis Thalassia hemprichii  pada beberapa kedalaman perairan. Sampel lamun diambil pada daerah subtidal, kemudian daun lamun dibersihkan dari sedimen dan epifit. Metode perubahan oksigen digunakan untuk mengestimasi serapan karbon. Sebanyak 1 tunas T. hemprichii diinkubasi menggunakan botol kaca bening 70 ml. Inkubasi dilakukan pada jam 09.00-12.00 WITA pada kedalaman 50, 100, 150, 200 dan 250 cm dengan masing-masing 5 kali ulangan setiap kedalaman. Sebelum inkubasi, dilakukan pengukuran konsentrasi oksigen terlarut di perairan sebagai kandungan oksigen awal. Pengukuran oksigen di dalam botol bening kembali dilakukan setelah inkubasi. Selain oksigen terlarut, dilakukan juga pengukuran konsentrasi bikarbonat pada awal dan akhir inkubasi. Sebagai kontrol, inkubasi juga dilakukan pada air laut (mengandung fitoplankton) dengan 5 kali ulangan. Daun lamun yang telah digunakan untuk pengamatan serapan karbon diukur luasnya dengan cara men-scan daun lamun dan dianalisis menggunakan software Imaje-J. Selanjutnya dilakukan pengeringan menggunakan oven dan ditimbang untuk mengetahui biomassa keringnya. Hasil penelitian menunjukkan bahwa serapan karbon per tunas berkisar antara 0,928-1,476 mgCO2/tunas/jam, per biomassa berkisar 10,647-25,745 mgCO2/gbk/jam, dan per luas daun berkisar 0,010-0,024 mgCO2/cm2/jam. Serapan karbon tertinggi didapatkan pada kedalaman 200 cm, baik serapan karbon per tunas, biomass maupun luas daun.

The activities of coastal and small islands communities can have an impact on the condition of the adjacent aquatic ecosystems. The magnitude of the impact depends on the type and intensity of the activities carried out. One ecosystem that is prone to be affected is the seagrass ecosystem due to its presence in shallow waters and proximity to the coast. The study was conducted to examine changes in seagrass carbon uptake on Bonebatang Island over a period of 16 years from 2001 to 2017. Estimation of carbon uptake of seven species of seagrasses, i.e., Enhalus acoroides, Thalassia hemprichii, Cymodocea rotundata, Halodule uninervis. Halophila ovalis, Halophila minor, and Syringodium isoetifolium were carried out using the oxygen change method that utilized clear bottles. The percentage of seagrass coverage was calculated using a 50cm x 50cm plot. The average composition of seagrass species from all plots and the capability of each seagrass species to uptake carbon was used as a basis to estimate the capability of seagrass to uptake the carbon per unit area. Changes in carbon uptake were determined using an approach that estimates changes in the seagrass bed areas. Landsat image analysis was used to estimate the area of seagrass in 2001, 2009, and 2017. The results showed that the area of seagrass beds in the period of 2001-2017 decreased by 8.62 ha, from 37.08 ha in 2001 to 28.46 ha in 2017 or decreased by approximately 1.54% per year. As a result of this diminishing in the area, carbon uptake by seagrasses was estimated to decrease by 19.67 MgCO2 per year from 79.62 MgCO2 per year in 2001 to 59.95 MgCO2 per year in 2017. The average decrease in a year reached 1.23 MgCO2.