Estimating sediment carbon stocks in the environment of Taiwan's coastal blue carbon system

The blue carbon system generally refers to the carbon sink environment that can be stored in the ocean system, and these environments are mainly mangroves, seagrass beds and salt marshes. This study investigates the second-largest seagrass bed in Kenting in Southern Taiwan. In addition to the advantages of high ecological diversity, seagrass beds are also considered to be a high carbon storage environment, which is more capable of sequestering carbon in the atmosphere than green carbon systems. In risk assessment, green carbon system may have fire risks, causing the sequestered carbon in plants to be released back into the atmosphere. Therefore, we believe that research on coastal blue carbon systems and carbon sequestration issues are better development goal and direction. To understand how much total organic carbon can be sequestered in seagrass bed sediments under natural growth, and to estimate how many tons of carbon equivalent (CO₂e) in the atmosphere the carbon sequestered in this area are our ultimate goal. In the choice of sampling sites, we collected two seagrass bed sediment cores about 40 cm long, namely core A (BH2-SG)(coring in the seagrass area), and core B (BH1-NSG)(coring in the bare area on the seagrass bed). The analysis results showed that the organic carbon content of sediment core A was 0.184-0.298 wt%, with an average content of 0.237 wt%, and that of sediment core B was 0.188-0.401 wt%, with an average content of 0.318 wt%. After plugging in the organic carbon accumulation content formula (MgC *ha^-1= (TOC(%)*depth(cm)*BD(g/cm³)), we can get the organic carbon accumulation values of sediment core A (13.539 MgC*ha^-1) and sediment core B (18.405 MgC*ha^-1). For now, we can only evaluate the carbon accumulation of the upper 40 cm seagrass bed sediments in this area. The average accumulated carbon content of the two cores is multiplied by the total area of the Kenting seagrass bed (about 4.38 ha), and then multiplied by the carbon dioxide equivalent coefficient 3.67 represents its carbon dioxide equivalent (CO₂e) (the content value is 256.49 CO₂e). At last, we consider that the area is a major factor affecting the amount of carbon storage. If we can increase seagrass area, more carbon can be stored in the sediment.

 

Keywords: Kenting, Taiwan, blue carbon system, seagrass bed, organic carbon content (TOC%), carbon dioxide equivalent (CO₂e)