Quantification of blue carbon storage in seagrass meadows across different management strategies in Lamu, Kenya

Abstract

Seagrass ecosystems play a crucial role in coastal carbon dynamics, yet their contribution to soil organic carbon (SOC) storage is underexplored in many areas and especially in African waters. This study assessed seagrass cover, species composition, and SOC stocks in the Lamu Archipelago, Kenya, comparing Marine Protected Areas (MPAs), Locally Managed Marine Areas (LMMAs), and unmanaged sites. Additionally, it investigated the relationships between management stratgeies and pertinent physical and chemical parameters. SOC was measured using the Loss on Ignition method and expressed as Mg C ha⁻¹. SOC stocks were higher in MPAs (89.16 ± 30.88 Mg C ha⁻¹) than in unmanaged areas, while SOC stocks in LMMAs were comparable to those in MPAs. While the MPA was associated with higher SOC stocks, these patterns may also reflect underlying environmental differences among sites, including sediment texture. SOC variability was strongly associated with sediment type, canopy cover, and disturbance intensity, with fine-grained sediments, particularly clay, linked to enhanced carbon retention. Higher SOC stocks co-occurred with the presence of large, persistent seagrass species such as Thalassodendron ciliatum and Enhalus acoroides in managed areas. This study provides the first field-based SOC estimates for Lamu's seagrass meadows, highlighting the potential of LMMAs within broader blue carbon conservation strategies.