Abstract:
This study examines daily carbon dioxide (CO₂) flux dynamics in a tropical seaweed farming system to evaluate its potential role in blue carbon sequestration. CO₂ flux measurements were conducted over the 40-day cultivation period using a static floating acrylic chamber. Daily CO₂ flux analysis was based on measurements conducted on cultivation days 20, 21, and 23, with gas samples collected at 6-hour intervals (morning, midday, and night). Samples were withdrawn using syringes, transferred into 10mL vacuum blood tubes, protected from direct sunlight, and analyzed using gas chromatography. CO₂ fluxes (mg CO₂ m⁻² min⁻¹) were calculated based on changes in gas concentration, chamber volume, surface area, and temperature. The results revealed a clear diurnal pattern, with negative CO₂ fluxes (uptake) observed during the morning and midday and positive fluxes (emission) occurring at night. This pattern reflects photosynthetic activity driven by daylight, confirming the role of seaweed as a photo-autotrophic organism that assimilates CO₂ into biomass, supported by the availability of dissolved nitrogen and phosphate. Over the cultivation period, CO₂ fluxes tended to become more negative, indicating enhanced carbon uptake associated with biomass growth. In comparison, non-seaweed areas exhibited lower but still negative CO₂ fluxes, likely attributable to phytoplankton photosynthesis. These findings indicate that tropical seaweed farming systems can function as effective carbon sinks, supporting their inclusion in blue carbon initiatives and coastal climate mitigation strategies.
