Integrating Multi-Scale Remote Sensing and Ground-Sampling to Map Seagrass Blue Carbon Stocks in Phu Quoc Island, Vietnam Xuan Truong Trinh (a*), Van Cong Doan (b,c), Quang-Loc Nguyen (d), Masahiko Nagai (e)
(a) Faculty of Engineering, Yamaguchi University, Japan
*trinh[at]yamaguchi-u.ac.jp
(b) Department of Life Sciences and Systems Biology, University of Turin, Italy
(c) Center for Climate Change Adaptation Research and Community Development Support, Tra Vinh University, Viet Nam
(d) Institute for Circular Economy Development, VNU-HCMC, Vietnam
(e) Yamaguchi University Center for Research and Application of Satellite Remote Sensing, Yamaguchi University, Japan
Abstract
Seagrass meadows are pivotal blue carbon ecosystems that play a critical role in climate change mitigation by sequestering atmospheric CO2 and trapping organic carbon in sediments. While Vietnam once supported over 36,000 hectares of seagrass, a significant decline to 17,000 hectares has been driven by rapid coastal development and aquaculture. The extensive 9,600-hectare seagrass meadow around Phu Quoc island, however, remains a crucial national asset. This study provides the first spatially explicit, high-resolution assessment of seagrass biomass and sediment carbon stocks for this vital ecosystem. Ultra high resolution UAV imagery was collected across the intertidal flat and classified using an object-based random forest approach. Ground surveys provided quadrat-level measurements of seagrass density, species composition and canopy height to calibrate UAV derived cover and biomass estimates. To characterise blue carbon stocks, eighteen aboveground and belowground biomass samples and eighteen sediment cores were collected across a gradient of seagrass densities. In the laboratory, samples were dried and processed using the Loss on Ignition method to determine organic matter and carbon content. Models were built to estimate seagrass biomass and carbon stocks based on their density, which was in turn used to generate continuous maps of seagrass biomass and carbon stocks across the 9,600 ha meadow. The resulting dataset establishes a fundamental baseline for blue carbon accounting in Vietnam and provides essential, data-driven insights for conservation management and policy. This research directly supports the Sustainable Development Goals (SDGs) by contributing to climate action, protecting life below water, and informing strategies for sustainable coastal development.
Keywords: Biomass, Loss on Ignition (LOI), Multi-scale analysis, Climate change mitigation, UAV
