Environmental heterogeneity and local drivers of seagrass sedimentary organic carbon on Bintan Island: A linear mixed-effects approach

Although seagrass meadows are significant blue carbon ecosystems in Indonesia and blue carbon studies have expanded rapidly in recent years, there is limited information on environmental factors and spatial variability of sediment organic carbon. Therefore, this study aims to examine sediment organic carbon concentrations in 2 regions of the seagrass meadows of Bintan Islands, Riau Islands Province Indonesia. The study procedures were carried out using nested by design data collection (site within region, zone within site and transect within zone). Key predictors of sediment organic carbon were identified and spatial variability was assessed using exploratory data analysis, linear mixed-effects models, and robust mixed-effects models. The results showed that there was significant spatial heterogeneity in sediment organic carbon, with the majority of variation occurring at larger spatial scales (region and site), while zone and transect levels showed relatively little variability. The most reliable indicator of sediment organic carbon concentrations, according to mixed-effects models, was the composition of sediment grains. Although it had lesser impact than sediment characteristics, seagrass density demonstrated a positive correlation with sediment organic carbon. After taking biological and sediment variables into consideration, regional differences persisted, indicating the significance of more comprehensive environmental controls. These findings indicate that sediment carbon variability is driven primarily by broad-scale spatial patterns and sediment properties rather than seagrass structural characteristics, showing the need for site and region specific management approaches.