Study of water-air CO2 gas exchange (CO2 flux) in seagrass ecosystems on the West Coast of Karimunjawa Island

The ocean plays a vital role in climate regulation. The purpose of this study was to determine the value of CO2 flux, determine the role of the seagrass ecosystem in Karimunjawa Island waters, and determine the factors that influence CO2 flux in Karimunjawa waters. This research was conducted in the western waters of the Karimunjawa Island seagrass ecosystem in August 2020 with survey and quantitative methods. Sampling was carried out at eight stations using the purposive sampling method. Physical, chemical and biological variables were measured, such as temperature, DO, salinity, phosphate, silicate and chlorophyll-a. The measurement of the carbonate system in this study was Total Alkalinity, DIC and pH. The partial pressure of CO2 in the oceans is calculated using the ocean pCO2 formula= 6.31T2+61.9Chl a2 – 365.85T - 94.41Chl a+5715.94 and the atmospheric CO2 partial pressure with the formula pCO2 atm=xCO2 atm (pb-H2O). Calculate CO2 flux using the formula: CO2 flux= Kh x kwa x (ΔpCO2). In general, the waters of the western Karimunjawa seagrass ecosystem act as CO2 releasers, the CO2 flux obtained from this study ranged from 15.60-26.36 mmol/m2/day. The flux flow is positive, where the CO2 flow moves from the ocean to the atmosphere. Based on PCA analysis, the CO2 flux has a close relationship with pCO2 water, with a correlation value of 0.884.