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In-situ measurements reveal alkalinity release from cold-temperate seagrass meadows

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Title: In-situ measurements reveal alkalinity release from cold-temperate seagrass meadows
Authors: Scott-Askin, Samuel, Santos, Isaac R., Albert, Gerli, Asplund, Maria E., Deyanova, Diana, Forsberg, Sara C., 1988, Ricart, Aurora M., Gullström, Martin, Björk, Mats, Reithmaier, Gloroa M. S.
Source: Estuarine, Coastal and Shelf Science. 326
Subject Terms: Benthic chamber, Blue carbon, Coastal carbon, Eelgrass, Porewater, Primary production, alkalinity, carbon sequestration, dissolved inorganic carbon, meadow, ocean acidification, seagrass meadow, Sweden
Description: Understanding the carbon sequestration potential of blue carbon ecosystems is important to inform climate policies and to guide restoration and protection efforts. Alkalinity generation is an often overlooked carbon sequestration mechanism, especially in seagrass meadows. Here, we quantified total alkalinity (TA) and dissolved inorganic carbon (DIC) fluxes in two cold-temperate Zostera marina seagrass meadows in Sweden using 24-h in-situ chamber incubations at the end of the high-productivity season. The seagrass meadows were similar net sources of TA (16 ± 45 mmol m−2 d−1 in Smalsund, 17 ± 16 mmol m−2 d−1 in Bökevik), whereas DIC fluxes were highly variable (34 ± 59 mmol m−2 d−1 in Smalsund, −43 ± 35 mmol m−2 d−1 in Bökevik). Fluxes followed a diurnal cycle consistent with photosynthesis-respiration cycles. As a result, seagrass meadows ameliorated ocean acidification locally during the day, but not during the night. The large CO2 uptake provided higher buffering levels compared to mangroves and saltmarshes. The TA fluxes were comparable to those reported for Mediterranean and tropical seagrass meadows, but 16-times lower than in mangrove forests and 5-times lower than in saltmarshes. Alkalinity generation in these cold-temperate seagrasses exceeded soil organic carbon stocks accumulation by fourfold, potentially contributing to their carbon sequestration potential and warranting inclusion in seagrass meadow carbon budgets.
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Access URL: https://urn.kb.se/resolve?urn=urn:nbn:se:sh:diva-58333
https://doi.org/10.1016/j.ecss.2025.109550
Database: SwePub
Description
Abstract:Understanding the carbon sequestration potential of blue carbon ecosystems is important to inform climate policies and to guide restoration and protection efforts. Alkalinity generation is an often overlooked carbon sequestration mechanism, especially in seagrass meadows. Here, we quantified total alkalinity (TA) and dissolved inorganic carbon (DIC) fluxes in two cold-temperate Zostera marina seagrass meadows in Sweden using 24-h in-situ chamber incubations at the end of the high-productivity season. The seagrass meadows were similar net sources of TA (16 ± 45 mmol m−2 d−1 in Smalsund, 17 ± 16 mmol m−2 d−1 in Bökevik), whereas DIC fluxes were highly variable (34 ± 59 mmol m−2 d−1 in Smalsund, −43 ± 35 mmol m−2 d−1 in Bökevik). Fluxes followed a diurnal cycle consistent with photosynthesis-respiration cycles. As a result, seagrass meadows ameliorated ocean acidification locally during the day, but not during the night. The large CO<inf>2</inf> uptake provided higher buffering levels compared to mangroves and saltmarshes. The TA fluxes were comparable to those reported for Mediterranean and tropical seagrass meadows, but 16-times lower than in mangrove forests and 5-times lower than in saltmarshes. Alkalinity generation in these cold-temperate seagrasses exceeded soil organic carbon stocks accumulation by fourfold, potentially contributing to their carbon sequestration potential and warranting inclusion in seagrass meadow carbon budgets.
DOI:10.1016/j.ecss.2025.109550