Warming enhances carbon dioxide and methane fluxes from Red Sea seagrass (Halophila stipulacea) sediments

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19 Scopus citations


Seagrass meadows are autotrophic ecosystems acting as carbon sinks, but they have also been shown to be sources of carbon dioxide (CO2) and methane (CH4). Seagrasses can be negatively affected by increasing seawater temperatures, but the effects of warming on CO2 and CH4 fluxes in seagrass meadows have not yet been reported. Here, we examine the effect of two disturbances on air-seawater fluxes of CO2 and CH4 in Red Sea Halophila stipulacea communities compared to adjacent unvegetated sediments using cavity ring-down spectroscopy. We first characterized CO2 and CH4 fluxes in vegetated and adjacent unvegetated sediments, and then experimentally examined their response, along with that of the carbon (C) isotopic signature of CO2 and CH4, to gradual warming from 25 C (winter seawater temperature) to 37C, 2 C above current maximum temperature. In addition, we assessed the response to prolonged darkness, thereby providing insights into the possible role of suppressing plant photosynthesis in supporting CO2 and CH4 fluxes. We detected 6-fold-higher CO2 fluxes in vegetated compared to bare sediments, as well as 10- to 100-fold-higher CH4 fluxes. Warming led to an increase in net CO2 and CH4 fluxes, reaching average fluxes of 10 422.18-2570.12 molCO2 m2 d1 and 88:11-15:19 molCH4 m2 d1, while CO2 and CH4 fluxes decreased over time in sediments maintained at 25-C. Prolonged darkness led to an increase in CO2 fluxes but a decrease in CH4 fluxes in vegetated sediments. These results add to previous research identifying Red Sea seagrass meadows as a significant source of CH4, while also indicating that sublethal warming may lead to increased emissions of greenhouse gases from seagrass meadows, providing a feedback mechanism that may contribute to further enhancing global warming.
Original languageEnglish (US)
Pages (from-to)1717-1730
Number of pages14
Issue number7
StatePublished - Apr 3 2020

Bibliographical note

KAUST Repository Item: Exported on 2020-10-01
Acknowledgements: We thank Paloma Carrillo de Albornoz, Mongi Ennasri and Vijayalaxmi Dasari for their help with analyses. We also thank Katherine Rowe and the Coastal and Marine Resources Core Lab (CMOR) for their assistance during field work and CMOR for their support with the experimental setup.


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