Please use this identifier to cite or link to this item: http://hdl.handle.net/10553/130953
Title: Ocean alkalinity enhancement using sodium carbonate salts does not lead to measurable changes in Fe dynamics in a mesocosm experiment
Authors: González Santana, David 
Segovia, Maria
Gonzalez-Davila, Melchor 
Ramirez, Librada
Gonzalez, Aridane G. 
Pozzo-Pirotta, Leonardo J.
Arnone, Veronica 
Vazquez, Victor
Riebesell ,Ulf 
Santana-Casiano, J. Magdalena 
UNESCO Clasification: 251002 Oceanografía química
Keywords: Cathodic stripping voltammetry
Binding ligands
Phaeodactylum-Tricornutum
Chemical speciation
Iron speciation, et al
Issue Date: 2024
Project: Ocean-based Negative Emission Technologies - analyzing the feasibility, risks, and cobenefits of ocean-based negative emission technologies for stabilizing the climate 
Journal: Biogeosciences 
Abstract: The addition of carbonate minerals to seawater through an artificial ocean alkalinity enhancement (OAE) process increases the concentrations of hydroxide, bicarbonate, and carbonate ions. This leads to changes in the pH and the buffering capacity of the seawater. Consequently, OAE could have relevant effects on marine organisms and in the speciation and concentration of trace metals that are essential for their physiology. During September and October 2021, a mesocosm experiment was carried out in the coastal waters of Gran Canaria (Spain), consisting on the controlled variation of total alkalinity (TA). Different concentrations of carbonate salts (NaHCO 3 and Na 2 CO 3 ) previously homogenized were added to each mesocosm to achieve an alkalinity gradient between Delta 0 to Delta 2400 mu mol L - 1 . The lowest point of the gradient was 2400 mu mol kg - 1 , being the natural alkalinity of the medium, and the highest point was 4800 mu mol kg - 1 . Iron (Fe) speciation was monitored during this experiment to analyse total dissolved iron (TdFe, unfiltered samples), dissolved iron (dFe, filtered through a 0.2 mu m pore size filter), soluble iron (sFe, filtered through a 0.02 mu m pore size filter), dissolved labile iron (dFe ' ), iron-binding ligands (LFe), and their conditional stability constants ( K FeL ' ) because of change due to OAE and the experimental conditions in each mesocosm. Observed iron concentrations were within the expected range for coastal waters, with no significant increases due to OAE. However, there were variations in Fe size fractionation during the experiment. This could potentially be due to chemical changes caused by OAE, but such an effect is masked by the stronger biological interactions. In terms of size fractionation, sFe was below 1.0 nmol L - 1 , dFe concentrations were within 0.5-4.0 nmol L - 1 , and TdFe was within 1.5-7.5 nmol L - 1 . Our results show that over 99 % of Fe was complexed, mainly by L 1 and L 2 ligands with k Fe ' L ' ranging between 10.92 +/- 0.11 and 12.68 +/- 0.32, with LFe ranging from 1.51 +/- 0.18 to 12.3 +/- 1.8 nmol L - 1 . Our data on iron size fractionation, concentration, and iron-binding ligands substantiate that the introduction of sodium salts in this mesocosm experiment did not modify iron dynamics. As a consequence, phytoplankton remained unaffected by alterations in this crucial element.
URI: http://hdl.handle.net/10553/130953
ISSN: 1726-4170
DOI: 10.5194/bg-21-2705-2024
Source: Biogeosciences [ISSN 1726-4170], v. 21 (11), p. 2705-2715, (Junio 2024)
Appears in Collections:Artículos
Adobe PDF (2,9 MB)
Show full item record

Google ScholarTM

Check

Altmetric


Share



Export metadata



Items in accedaCRIS are protected by copyright, with all rights reserved, unless otherwise indicated.