Inorganic carbon outwelling from a Mediterranean seagrass meadow using radium isotopes

Seagrass meadows are ‘blue carbon’ ecosystems widely recognised for their potential role in climate change mitigation. Previous studies have focused mainly on carbon storage within and sediments. However, little is known about contribution of outwelling (i.e., lateral transport) to seagrass budgets. Here, radium isotopes (223Ra 224Ra) were used assess dissolved inorganic (DIC) total alkalinity (TA) from a Mediterranean Posidonia oceanica meadow during early autumn. DIC was 114 ± 61 mmol m−2 day−1 exceeded above-meadow CO2 outgassing (3 1 day−1). Production uncoupled TA fuelled by net heterotrophy aerobic processes the meadow. The small export (5 6 day−1) implied that ∼90% outwelled may return atmosphere as offshore waters. Combining these fluxes with suggested loss long term burial Overall, acted source autumn season. Further quantifying at multiple spatial temporal scales required better resolve budgets sequestration.