Seagrass blue carbon spatial patterns at the meadow-scale.

Area of Science:

• Marine ecology
• Blue carbon research
• Seagrass ecosystem dynamics

Background:

• Seagrass meadows are vital carbon sinks, but estimates of their carbon burial capacity often rely on limited point measurements.
• Spatial variability in sediment organic carbon (Corg) concentrations, particularly gradients from meadow edges, can impact the accuracy of carbon stock assessments.

Purpose of the Study:

• To map sediment Corg concentrations across a large restored seagrass meadow (6 km²) to identify spatial distribution patterns.
• To determine if Corg distribution is influenced by proximity to the meadow edge or meadow age.
• To quantify the enhanced carbon stock resulting from seagrass restoration.

Main Methods:

• Spatial mapping of sediment Corg concentrations within a 6 km² restored seagrass meadow.
• Application of spatial autoregressive models to analyze Corg distribution relative to edge proximity and meadow age.
• Evaluation of Corg correlations with explanatory variables like shoot density, grain size, and bathymetry.

Main Results:

• Edge proximity, not meadow age, was a significant predictor of meadow-scale Corg distribution.
• Factors like shoot density and age, significant at plot scales, did not control meadow-scale Corg distribution.
• Strong correlations between Corg, grain size, and edge proximity indicate increased fine-sediment deposition and carbon burial deeper within the meadow.

Conclusions:

• Seagrass restoration demonstrably enhances blue carbon stocks, with the studied meadow containing approximately 1200 t more Corg than bare sediment.
• Carbon burial is influenced by meadow configuration and tidal current velocities, with higher accumulation in areas of low currents.
• Large, contiguous seagrass meadows are likely to store more blue carbon than fragmented, smaller patches.