Abstract
Valuing sedimentary 'blue carbon' stocks of seagrass meadows requires exclusion of allochthonous recalcitrant forms of carbon, such as black carbon (BC). Regression models constructed across a Southeast Asian tropical estuary predicted that carbon stocks within the sandy meadows of coastal embayments would support a modest but not insignificant amount of BC. We tested the prediction across three coastal meadows of the same region: one patchy meadow located close to a major urban centre and two continuous meadows contained in separate open embayments of a rural marine park; all differed in fetch and species. The BC/total organic carbon (TOC) fractions in the urban and rural meadows with small canopies were more than double the predicted amounts, 28 ± 1.6% and 36 ± 1.5% (±95% confidence intervals), respectively. The fraction in the rural large-canopy meadow remained comparable to the other two meadows, 26 ± 4.9% (±95% confidence intervals) but was half the amount predicted, likely owing to confounding of the model. The relatively high BC/TOC fractions were explained by variability across sites of BC atmospheric supply, an increase in loss of seagrass litter close to the exposed edges of meadows and sediment resuspension across the dispersed patchy meadow.
Highlights
The effect of anthropogenic emissions of CO2 on the climate highlights the importance of quantifying and managing existing sedimentary organic carbon stocks
Seagrass canopy can trap soils eroded from adjacent landscapes, which can account for as much as 50% of total sedimentary organic stocks [6] that would otherwise be remineralized across the continental shelf [7]
This study examines the above estuarine predictions and likely controlling factors across coastal meadows in Southeast Asia (Sabah, Malaysia)
Summary
The effect of anthropogenic emissions of CO2 on the climate highlights the importance of quantifying and managing existing sedimentary organic carbon stocks. The focus has turned to ‘blue carbon’ reservoirs—seagrass, saltmarsh, mangrove and macro-algae ecosystems [1,2]. Together, these store half the ocean’s total organic carbon (TOC), despite occupying less than 2% of the area [3]. These store half the ocean’s total organic carbon (TOC), despite occupying less than 2% of the area [3] This disproportionate contribution results from their high rates of primary production and ability to enhance and stabilize the accumulation of deposited litter and detritus and prevent it from remineralizing, ostensibly back to CO2 [4,5]. Seagrass canopy can trap soils eroded from adjacent landscapes, which can account for as much as 50% of total sedimentary organic stocks [6] that would otherwise be remineralized across the continental shelf [7]
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