Biogeochemical feedbacks to ocean acidification in a cohesive photosynthetic sediment

Abstract Ecosystem feedbacks in response to ocean acidification can amplify or diminish diel pH oscillations in productive coastal waters. Benthic microalgae generate such oscillations in sediment porewater and here we ask how CO2 enrichment (acidification) of the overlying seawater alters these in...

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Autores principales:	Kay Vopel, Alexis Marshall, Shelly Brandt, Adam Hartland, Charles K. Lee, S. Craig Cary, Conrad A. Pilditch
Formato:	article
Lenguaje:	EN
Publicado:	Nature Portfolio 2021
Materias:	Medicine R Science Q
Acceso en línea:	https://doaj.org/article/2743133563da4a60b26e055ab85ca79b
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spelling	oai:doaj.org-article:2743133563da4a60b26e055ab85ca79b2021-11-28T12:19:02ZBiogeochemical feedbacks to ocean acidification in a cohesive photosynthetic sediment10.1038/s41598-021-02314-y2045-2322https://doaj.org/article/2743133563da4a60b26e055ab85ca79b2021-11-01T00:00:00Zhttps://doi.org/10.1038/s41598-021-02314-yhttps://doaj.org/toc/2045-2322Abstract Ecosystem feedbacks in response to ocean acidification can amplify or diminish diel pH oscillations in productive coastal waters. Benthic microalgae generate such oscillations in sediment porewater and here we ask how CO2 enrichment (acidification) of the overlying seawater alters these in the absence and presence of biogenic calcite. We placed a 1-mm layer of ground oyster shells, mimicking the arrival of dead calcifying biota (+Calcite), or sand (Control) onto intact silt sediment cores, and then gradually increased the pCO2 in the seawater above half of +Calcite and Control cores from 472 to 1216 μatm (pH 8.0 to 7.6, CO2:HCO3 − from 4.8 to 9.6 × 10−4). Porewater [O2] and [H+] microprofiles measured 16 d later showed that this enrichment had decreased the O2 penetration depth (O2-pd) in +Calcite and Control, indicating a metabolic response. In CO2-enriched seawater: (1) sediment biogeochemical processes respectively added and removed more H+ to and from the sediment porewater in darkness and light, than in ambient seawater increasing the amplitude of the diel porewater [H+] oscillations, and (2) in darkness, calcite dissolution in +Calcite sediment decreased the porewater [H+] below that in overlying seawater, reversing the sediment–seawater H+ flux and decreasing the amplitude of diel [H+] oscillations. This dissolution did not, however, counter the negative effect of CO2 enrichment on O2-pd. We now hypothesise that feedback to CO2 enrichment—an increase in the microbial reoxidation of reduced solutes with O2—decreased the sediment O2-pd and contributed to the enhanced porewater acidification.Kay VopelAlexis MarshallShelly BrandtAdam HartlandCharles K. LeeS. Craig CaryConrad A. PilditchNature PortfolioarticleMedicineRScienceQENScientific Reports, Vol 11, Iss 1, Pp 1-12 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	Medicine R Science Q
spellingShingle	Medicine R Science Q Kay Vopel Alexis Marshall Shelly Brandt Adam Hartland Charles K. Lee S. Craig Cary Conrad A. Pilditch Biogeochemical feedbacks to ocean acidification in a cohesive photosynthetic sediment
description	Abstract Ecosystem feedbacks in response to ocean acidification can amplify or diminish diel pH oscillations in productive coastal waters. Benthic microalgae generate such oscillations in sediment porewater and here we ask how CO2 enrichment (acidification) of the overlying seawater alters these in the absence and presence of biogenic calcite. We placed a 1-mm layer of ground oyster shells, mimicking the arrival of dead calcifying biota (+Calcite), or sand (Control) onto intact silt sediment cores, and then gradually increased the pCO2 in the seawater above half of +Calcite and Control cores from 472 to 1216 μatm (pH 8.0 to 7.6, CO2:HCO3 − from 4.8 to 9.6 × 10−4). Porewater [O2] and [H+] microprofiles measured 16 d later showed that this enrichment had decreased the O2 penetration depth (O2-pd) in +Calcite and Control, indicating a metabolic response. In CO2-enriched seawater: (1) sediment biogeochemical processes respectively added and removed more H+ to and from the sediment porewater in darkness and light, than in ambient seawater increasing the amplitude of the diel porewater [H+] oscillations, and (2) in darkness, calcite dissolution in +Calcite sediment decreased the porewater [H+] below that in overlying seawater, reversing the sediment–seawater H+ flux and decreasing the amplitude of diel [H+] oscillations. This dissolution did not, however, counter the negative effect of CO2 enrichment on O2-pd. We now hypothesise that feedback to CO2 enrichment—an increase in the microbial reoxidation of reduced solutes with O2—decreased the sediment O2-pd and contributed to the enhanced porewater acidification.
format	article
author	Kay Vopel Alexis Marshall Shelly Brandt Adam Hartland Charles K. Lee S. Craig Cary Conrad A. Pilditch
author_facet	Kay Vopel Alexis Marshall Shelly Brandt Adam Hartland Charles K. Lee S. Craig Cary Conrad A. Pilditch
author_sort	Kay Vopel
title	Biogeochemical feedbacks to ocean acidification in a cohesive photosynthetic sediment
title_short	Biogeochemical feedbacks to ocean acidification in a cohesive photosynthetic sediment
title_full	Biogeochemical feedbacks to ocean acidification in a cohesive photosynthetic sediment
title_fullStr	Biogeochemical feedbacks to ocean acidification in a cohesive photosynthetic sediment
title_full_unstemmed	Biogeochemical feedbacks to ocean acidification in a cohesive photosynthetic sediment
title_sort	biogeochemical feedbacks to ocean acidification in a cohesive photosynthetic sediment
publisher	Nature Portfolio
publishDate	2021
url	https://doaj.org/article/2743133563da4a60b26e055ab85ca79b
work_keys_str_mv	AT kayvopel biogeochemicalfeedbackstooceanacidificationinacohesivephotosyntheticsediment AT alexismarshall biogeochemicalfeedbackstooceanacidificationinacohesivephotosyntheticsediment AT shellybrandt biogeochemicalfeedbackstooceanacidificationinacohesivephotosyntheticsediment AT adamhartland biogeochemicalfeedbackstooceanacidificationinacohesivephotosyntheticsediment AT charlesklee biogeochemicalfeedbackstooceanacidificationinacohesivephotosyntheticsediment AT scraigcary biogeochemicalfeedbackstooceanacidificationinacohesivephotosyntheticsediment AT conradapilditch biogeochemicalfeedbackstooceanacidificationinacohesivephotosyntheticsediment
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Biogeochemical feedbacks to ocean acidification in a cohesive photosynthetic sediment

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