View in EDS

Carbon fixation of a temperate plankton community in response to calcium- and silicate-based Ocean Alkalinity Enhancement using air-sea gas exchange measurements.

Saved in:
Bibliographic Details
Title: Carbon fixation of a temperate plankton community in response to calcium- and silicate-based Ocean Alkalinity Enhancement using air-sea gas exchange measurements.
Authors: Schneider, Julieta, Riebesell, Ulf, Moras, Charly André, Marín-Samper, Laura, Kittu, Leila Richards, Ortíz-Cortes, Joaquín, Schulz, Kai Georg
Source: Biogeosciences; 2026, Vol. 23 Issue 1, p137-153, 17p
Abstract: Ocean Alkalinity Enhancement (OAE) is a carbon dioxide removal strategy that aims to chemically sequester atmospheric CO2 in the ocean while potentially alleviating localized effects of ocean acidification. Depending on the implementation approach, OAE can considerably alter seawater carbonate chemistry, resulting in temporarily reduced CO2 partial pressure (p CO2) and elevated pH before re-equilibration with the atmosphere or mixing with unperturbed waters. To investigate the effects of OAE on biogeochemical processes and organisms under close-to-natural conditions, a large-scale mesocosm experiment was conducted in a temperate fjord ecosystem near Bergen, Norway, during late spring. A non-CO2-equilibrated OAE approach was chosen, simulating OAE with calcium- and silicate-based minerals. A gradient of five OAE levels was achieved by increasing total alkalinity (TA) by 0–600 µmolkg-1. The added TA remained relatively stable over the 47 d experiment and measured CO2 gas exchange rates reached up to -15 mmol C m−2 d−1. We estimated that full equilibration (95 %) by air-sea gas exchange for a Δ TA of 600 µmolkg-1 would take ∼1050 d. Furthermore, various mineral-type and/or p CO2 / pH effects were found. Coccolithophore calcification followed an optimum curve response along the p CO2 gradient, consistent with findings from single-species laboratory cultures. In contrast, in-situ net community production (NCP) was higher in the silicate-based treatments, but was not modified by changes in p CO2. Zooplankton respiration, estimated from in-situ NCP and in-vitro NCP incubations, was lower for the silicate-based treatments and negatively correlated with p CO2. These complex findings suggest both direct and indirect effects of mineral type and OAE level and provide a valuable foundation for designing future OAE field trials. For a safe application of OAE, non-equilibrated alkalinity additions must balance efficiency and environmental impact. [ABSTRACT FROM AUTHOR]
Copyright of Biogeosciences is the property of Copernicus Gesellschaft mbH and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
Database: Complementary Index
Description
Abstract:Ocean Alkalinity Enhancement (OAE) is a carbon dioxide removal strategy that aims to chemically sequester atmospheric CO<subscript>2</subscript> in the ocean while potentially alleviating localized effects of ocean acidification. Depending on the implementation approach, OAE can considerably alter seawater carbonate chemistry, resulting in temporarily reduced CO<subscript>2</subscript> partial pressure (p CO<subscript>2</subscript>) and elevated pH before re-equilibration with the atmosphere or mixing with unperturbed waters. To investigate the effects of OAE on biogeochemical processes and organisms under close-to-natural conditions, a large-scale mesocosm experiment was conducted in a temperate fjord ecosystem near Bergen, Norway, during late spring. A non-CO<subscript>2</subscript>-equilibrated OAE approach was chosen, simulating OAE with calcium- and silicate-based minerals. A gradient of five OAE levels was achieved by increasing total alkalinity (TA) by 0–600 µmolkg-1. The added TA remained relatively stable over the 47 d experiment and measured CO<subscript>2</subscript> gas exchange rates reached up to -15 mmol C m<sup>−2</sup> d<sup>−1</sup>. We estimated that full equilibration (95 %) by air-sea gas exchange for a Δ TA of 600 µmolkg-1 would take ∼1050 d. Furthermore, various mineral-type and/or p CO<subscript>2</subscript> / pH effects were found. Coccolithophore calcification followed an optimum curve response along the p CO<subscript>2</subscript> gradient, consistent with findings from single-species laboratory cultures. In contrast, in-situ net community production (NCP) was higher in the silicate-based treatments, but was not modified by changes in p CO<subscript>2</subscript>. Zooplankton respiration, estimated from in-situ NCP and in-vitro NCP incubations, was lower for the silicate-based treatments and negatively correlated with p CO<subscript>2</subscript>. These complex findings suggest both direct and indirect effects of mineral type and OAE level and provide a valuable foundation for designing future OAE field trials. For a safe application of OAE, non-equilibrated alkalinity additions must balance efficiency and environmental impact. [ABSTRACT FROM AUTHOR]
ISSN:17264170
DOI:10.5194/bg-23-137-2026