AACL Bioflux, 2017, Volume 10, Issue 5. http://www.bioflux.com.ro/aacl 1019 Seagrass potency as blue carbon source in Galala and Tanjung Tiram waters, Ambon Island, Indonesia Mahriyana Hulopi, Juliana W. Tuahatu, Novianty C. Tuhumury Department of Aquatic Resource Management, Faculty of Fishery and Marine Science, Pattimura University, Ambon, Indonesia. Corresponding author: M. Hulopi, mhulopi75@gmail.com Abstract . Seagrass ecosystem is one of the important ecosystems in tropical coastal areas apart from mangrove and coral reefs. Seagrass has been considered recently as one of the potential carbon dioxide ( CO 2 ) absorbent that significantly contribute to reduce CO 2 concentration in atmosphere in attempt to eliminate global climate change. This research is aimed to analyze the organic carbon (C-organic) content in seagrass bed at Galala and Tanjung Tiram waters of Ambon Island, Indonesia. C-organic content was analyzed at leaf, sheath, root and rhizome of each species found. Lost on Ignition (LOI) method was used to analyze organic carbon content. Result shows that seagrass of the species Enhalus acoroides found in Galala water has the highest organic carbon at rhizome amounted for 48.3%. Of all 4 species found in Tanjung Tiram,waters almost the highest organic carbon was found at rhizome of that species. Overall, it can be concluded that the highest percentage of organic carbon content in E. acoroides found in Galala waters was at below ground and the lowest percentage was at above ground. On the other hand, E. acoroides was having higher percentage of organic carbon content at above ground than that of Halophila ovalis in Tanjung Tiram waters. While at below ground the highest percentage organic carbon content was found at Halodule uninervis and the lowest at H. ovalis. Key Words: blue carbon, C-organic, seagrass, rhizome. Introduction . Increase in human population all together with their activities especially in coastal area will give an impact on ecosystem performance in this area. According to population number of Ambon City, Indonesia, population growth rate of Ambon city was 3.75 yr -1 , which is the highest one compared to other districts of Maluku Province (Centre Bureau of Statistics 2016). The higher the population growth rate will in turn increase ecological pressure on coastal area particularly in small islands like Ambon. Ecological pressure in coastal area contributes to decrease in biodiversity of three important tropical ecosystem i.e. seagrass, mangrove and coral. These three ecosystems support many organisms associate with it, some being of economic importance, that contributing to food security of the community. Some studies have shown an increase in human activities in coastal area of Ambon city which has little intention on sustainability theses ecosystems that lead to decrease in seagrass and mangrove ecosystem performance (Tuhumury 2008; Suyadi 2009; Siahainenia et al 2014). Seagrass ecosystem is one of the important coastal ecosystems found in Maluku Province. Some ecological functions of seagrass ecosystem are nursery ground, feeding ground, and spawning ground of many organisms (Jackson et al 2001; Orth et al 2006; Unsworth et al 2014). Recent studies have shown that seagrass can absorb substantial carbon emission (Duarte et al 2005; Nellemann et al 2009; Kiswara 2010). Many scientists have discussed a way in reducing carbon emission and come up with the concept of blue carbon which stated that three marine ecosystems (mangrove, seagrass and salt marsh) have the ability to maintain absorption balance and decrease of carbon emission (Nellemann et al 2009). Condition of seagrass bed in Ambon Bay has decreased tremendously which cause the ability of its function in absorbing carbon has also decreased. The only sea grass