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Coastal tidal wetlands and estuaries play important roles in the global carbon budget by contributing to the net withdrawal of CO2from the atmosphere. We quantified the linkages between terrestrial and oceanic systems, marsh-to-bay carbon exchange, and the uptake of CO2from the atmosphere in the wetland-dominated Plum Island Sound (MA, USA) and Duplin River (GA, USA) estuaries. The C budgets revealed that autotrophic marshes [primary production:ecosystem respiration (P:R) ~1.3:1] are tightly coupled to heterotrophic aquatic systems (P:R ~0.6:1). Levels of marsh gross primary production are similar in these systems (865 ± 39 and 768 ± 74 gC m−2year−1in Plum Island and the Duplin, respectively) even though they are in different biogeographic provinces. In contrast to inputs from rivers and coastal oceans, tidal marshes are the dominant source of allochthonous matter that supports heterotrophy in aquatic systems. Dissolved inorganic carbon (DIC) exported from marshes to the coastal ocean was a major flux pathway in the Duplin River; however, there was no evidence of DIC export from Plum Island marshes and only minor export to the ocean. Burial was a sink for 53% of marsh net ecosystem production (NEP) on Plum Island, but only 19% of marsh NEP in the Duplin. Burial was the dominant blue carbon sequestration pathway at Plum Island, whereas in the Duplin, DIC and organic carbon export to the ocean were equally important. Regional- and continental-scale C budgets should better reflect wetland-dominated systems to more accurately characterize their contribution to global CO2sequestration.
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This content will become publicly available on April 4, 2026
Riverine photosynthesis influences the carbon sequestration potential of enhanced rock weathering
As climate mitigation efforts lag, dependence on anthropogenic CO2removal increases. Enhanced rock weathering (ERW) is a rapidly growing CO2removal approach. In terrestrial ERW, crushed rocks are spread on land where they react with CO2and water, forming dissolved inorganic carbon (DIC) and alkalinity. For long-term sequestration, these products must travel through rivers to oceans, where carbon remains stored for over 10,000 years. Carbon and alkalinity can be lost during river transport, reducing ERW efficacy. However, the ability of biological processes, such as aquatic photosynthesis, to affect the fate of DIC and alkalinity within rivers has been overlooked. Our analysis indicates that within a stream-order segment, aquatic photosynthesis uptakes 1%–30% of DIC delivered by flow for most locations. The effect of this uptake on ERW efficacy, however, depends on the cell-membrane transport mechanism and the fate of photosynthetic carbon. Different pathways can decrease just DIC, DIC and alkalinity, or just alkalinity, and the relative importance of each is unknown. Further, data show that expected river chemistry changes from ERW may stimulate photosynthesis, amplifying the importance of these biological processes. We argue that estimating ERW’s carbon sequestration potential requires consideration and better understanding of biological processes in rivers.
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- PAR ID:
- 10585072
- Publisher / Repository:
- Frontiers
- Date Published:
- Journal Name:
- Frontiers in Climate
- Volume:
- 7
- ISSN:
- 2624-9553
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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