Influence of Environmental Factors on pH Buffering, Productivity, and Blue Carbon Storage in Contrasting Thalassia Testudinum Seagrass Meadows in La Parguera, Puerto Rico
A comparative study of two Thalassia testudinum meadows in Puerto Rico reveals that low‑flow nearshore seagrass beds adjacent to mangroves provide stronger pH buffering, higher productivity, greater biomass, and significantly larger carbon stocks than offshore high‑flow meadows. Cross‑ecosystem connectivity shapes their climate‑mitigating capacity.
Subject Tags
- Mangroves
- Coastal
- Climate mitigation
Abstract
Seagrass meadows provide important ecosystem services including pH buffering and blue carbon storage. However, our understanding of the ability of seagrass meadows to mitigate climate change effects and maintain their ecological function remains limited by the lack of studies simultaneously quantifying the rates and environmental drivers of seagrass pH buffering, productivity, biomass, and blue carbon storage. The present study addresses this through a combination of deploying in situ environmental sensors and conducting spatial seawater chemistry surveys at the same time as seagrass cover surveys, productivity assessments, biomass cores, and sediment cores at two contrasting Thalassia testudinum meadows in La Parguera Nature Reserve, Puerto Rico: a low-flow nearshore site adjacent to mangroves (Isla Magueyes) and a moderate-flow offshore site adjacent to a coral reef (Cayo Laurel). Both sites exhibited similar environmental variability, although the nearshore site showed lower irradiance reaching the seagrass canopy (422 ± 375 vs. 469 ± 435 µmol m⁻² s⁻¹), slower flow speeds (0.3 ± 0.2 vs. 5.3 ± 3.3 vs. cm/s), warmer temperatures (30.5 ± 0.3 vs. 30.0 ± 0.4 °C), and lower dissolved oxygen (5.5 ± 1.1 vs. 6 ± 1.1 mg/L) compared to the offshore site. Both sites were dominated by organic carbon cycling (nTA: nDIC slopes ~ 0), yet spatial pH buffering gradients were only detected at the nearshore site, likely because the higher flow speeds offshore flushed water before pH changes could accumulate to detectable levels. Seagrass productivity (7.6 ± 0.8 vs. 3.3 ± 0.4 gDW/m²/day), aboveground biomass (106 ± 25 vs. 60 ± 23 gDW/m²), and sediment organic carbon stocks (78.20 vs. 21.63 MgC/ha) were all significantly greater at the nearshore site, likely due to enhanced nutrient availability, proximity to mangroves, and reduced flow speeds. The nearshore seagrass meadows located in a low-flow environment adjacent to mangroves exhibited greater capacity for pH buffering and organic carbon storage than the offshore seagrass meadow in a high-flow environment adjacent to a coral reef, emphasizing the critical role of cross-ecosystem connectivity in shaping ecosystem function.
Citation
Rodríguez, C. H., Reyes, J. C., Perez, D. I., Gonzalez-Corredor, J., Krause, J. R., Campbell, J. E., ... & Courtney, T. A. (2026). Influence of Environmental Factors on pH Buffering, Productivity, and Blue Carbon Storage in Contrasting Thalassia Testudinum Seagrass Meadows in La Parguera, Puerto Rico. Estuaries and Coasts, 49(2), 40.
TNC Authors
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Denise Perez
Spatial Ecologist, Caribbean Div • Caribbean
The Nature Conservancy
Email: denise.perez@tnc.org