The influence of seagrass and its associated sediment on organic carbon storage: A case of Halodule uninervis and Syringodium isoetifolium meadows of Western India Ocean, Tanzania.

Seagrass meadows are considered crucial natural carbon stocks. However, in Tanzania, few species have been assessed for their potential carbon stocks and variability in percentage organic carbon (%Corg) stocks. The study reports the contributions of seagrasses Halodule uninervis and Syringodium isoetifolium in carbon storage in WIO region. Findings revealed a significantly higher %Corg in seagrass meadows compared to unvegetated, confirming that seagrass heightens organic carbon storage. The seagrass carbon storage varied significantly among sites ranging from 4.05 ± 0.7% in Kaole to 0.62 ± 0.05% in Kunduchi. Syringodium isoetifolium meadows had higher organic carbon (p = 0.002) than H. uninervis. The partial least square analysis showed that below- and aboveground biomass and canopy height were positively correlated to %Corg. Sediment density and porosity were the vital predictor but negatively correlated with %Corg. The study showed a higher %Corg in the marine protected area, which could be linked to seagrass structural complexities and sediment porosity.