Vivianite formation in methane-rich deep-sea sediments from the South China Sea
<p>Phosphorus is often invoked as the ultimate limiting nutrient, modulating primary productivity on geological timescales. Consequently, along with nitrogen, phosphorus bioavailability exerts a fundamental control on organic carbon production, linking all the biogeochemical cycles across t...
| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2018-10-01
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| Series: | Biogeosciences |
| Online Access: | https://www.biogeosciences.net/15/6329/2018/bg-15-6329-2018.pdf |
| _version_ | 1819106338082390016 |
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| author | J. Liu G. Izon J. Wang G. Antler G. Antler G. Antler Z. Wang J. Zhao M. Egger |
| author_facet | J. Liu G. Izon J. Wang G. Antler G. Antler G. Antler Z. Wang J. Zhao M. Egger |
| author_sort | J. Liu |
| collection | DOAJ |
| description | <p>Phosphorus is often invoked as the ultimate limiting nutrient,
modulating primary productivity on geological timescales. Consequently, along
with nitrogen, phosphorus bioavailability exerts a fundamental control on
organic carbon production, linking all the biogeochemical cycles across the
Earth system. Unlike nitrogen that can be microbially fixed from an
essentially infinite atmospheric reservoir, phosphorus availability is
dictated by the interplay between its sources and sinks. While authigenic
apatite formation has received considerable attention as the dominant
sedimentary phosphorus sink, the quantitative importance of reduced
iron-phosphate minerals, such as vivianite, has only recently been
acknowledged, and their importance remains underexplored. Combining
microscopic and spectroscopic analyses of handpicked mineral aggregates with
sediment geochemical profiles, we characterize the distribution and
mineralogy of iron-phosphate minerals present in methane-rich sediments
recovered from the northern South China Sea. Here, we demonstrate that
vivianite authigenesis is pervasive in the iron-oxide-rich sediments below
the sulfate–methane transition zone (SMTZ). We hypothesize that the downward
migration of the SMTZ concentrated vivianite formation below the current
SMTZ. Our observations support recent findings from non-steady-state
post-glacial sedimentary successions, suggesting that iron reduction below
the SMTZ, probably driven by iron-mediated anaerobic oxidation of methane
(Fe-AOM), is coupled to phosphorus cycling on a much greater spatial scale
than previously assumed. Calculations reveal that vivianite acts as an
important burial phase for both iron and phosphorus below the SMTZ,
sequestering approximately half of the total reactive iron pool. By
extension, sedimentary vivianite formation could serve as a mineralogical
marker of Fe-AOM, signalling low-sulfate availability against methanogenic
and ferruginous backdrop. Given that similar conditions were likely present
throughout vast swathes of Earth's history, it is possible that Fe-AOM and
vivianite authigenesis may have modulated methane and phosphorus availability
on the early Earth, as well as during later periods of expanded marine oxygen
deficiency. A better understanding of vivianite authigenesis, therefore, is
fundamental to test long-standing hypotheses linking climate, atmospheric
chemistry and the evolution of the biosphere.</p> |
| first_indexed | 2024-12-22T02:36:33Z |
| format | Article |
| id | doaj.art-3f773004b0cd4bc096e6f927413ea6f5 |
| institution | Directory Open Access Journal |
| issn | 1726-4170 1726-4189 |
| language | English |
| last_indexed | 2024-12-22T02:36:33Z |
| publishDate | 2018-10-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Biogeosciences |
| spelling | doaj.art-3f773004b0cd4bc096e6f927413ea6f52022-12-21T18:41:44ZengCopernicus PublicationsBiogeosciences1726-41701726-41892018-10-01156329634810.5194/bg-15-6329-2018Vivianite formation in methane-rich deep-sea sediments from the South China SeaJ. Liu0G. Izon1J. Wang2G. Antler3G. Antler4G. Antler5Z. Wang6J. Zhao7M. Egger8State Key Laboratory of Biogeology and Environment Geology, College of Marine Science and Technology, School of Earth Sciences, China University of Geosciences, Wuhan, 430074, ChinaDepartment of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USAState Key Laboratory of Biogeology and Environment Geology, College of Marine Science and Technology, School of Earth Sciences, China University of Geosciences, Wuhan, 430074, ChinaDepartment of Geological and Environmental Sciences, Ben-Gurion University of the Negev, Beersheba, 84105, IsraelThe Interuniversity Institute for Marine Sciences, Eilat, 88103, IsraelDepartment of Earth Sciences, University of Cambridge, Cambridge, CB2 3EQ, UKState Key Laboratory of Biogeology and Environment Geology, College of Marine Science and Technology, School of Earth Sciences, China University of Geosciences, Wuhan, 430074, ChinaState Key Laboratory of Biogeology and Environment Geology, College of Marine Science and Technology, School of Earth Sciences, China University of Geosciences, Wuhan, 430074, ChinaThe Ocean Cleanup Foundation, Rotterdam, 3014 JH, the Netherlands<p>Phosphorus is often invoked as the ultimate limiting nutrient, modulating primary productivity on geological timescales. Consequently, along with nitrogen, phosphorus bioavailability exerts a fundamental control on organic carbon production, linking all the biogeochemical cycles across the Earth system. Unlike nitrogen that can be microbially fixed from an essentially infinite atmospheric reservoir, phosphorus availability is dictated by the interplay between its sources and sinks. While authigenic apatite formation has received considerable attention as the dominant sedimentary phosphorus sink, the quantitative importance of reduced iron-phosphate minerals, such as vivianite, has only recently been acknowledged, and their importance remains underexplored. Combining microscopic and spectroscopic analyses of handpicked mineral aggregates with sediment geochemical profiles, we characterize the distribution and mineralogy of iron-phosphate minerals present in methane-rich sediments recovered from the northern South China Sea. Here, we demonstrate that vivianite authigenesis is pervasive in the iron-oxide-rich sediments below the sulfate–methane transition zone (SMTZ). We hypothesize that the downward migration of the SMTZ concentrated vivianite formation below the current SMTZ. Our observations support recent findings from non-steady-state post-glacial sedimentary successions, suggesting that iron reduction below the SMTZ, probably driven by iron-mediated anaerobic oxidation of methane (Fe-AOM), is coupled to phosphorus cycling on a much greater spatial scale than previously assumed. Calculations reveal that vivianite acts as an important burial phase for both iron and phosphorus below the SMTZ, sequestering approximately half of the total reactive iron pool. By extension, sedimentary vivianite formation could serve as a mineralogical marker of Fe-AOM, signalling low-sulfate availability against methanogenic and ferruginous backdrop. Given that similar conditions were likely present throughout vast swathes of Earth's history, it is possible that Fe-AOM and vivianite authigenesis may have modulated methane and phosphorus availability on the early Earth, as well as during later periods of expanded marine oxygen deficiency. A better understanding of vivianite authigenesis, therefore, is fundamental to test long-standing hypotheses linking climate, atmospheric chemistry and the evolution of the biosphere.</p>https://www.biogeosciences.net/15/6329/2018/bg-15-6329-2018.pdf |
| spellingShingle | J. Liu G. Izon J. Wang G. Antler G. Antler G. Antler Z. Wang J. Zhao M. Egger Vivianite formation in methane-rich deep-sea sediments from the South China Sea Biogeosciences |
| title | Vivianite formation in methane-rich deep-sea sediments from the South China Sea |
| title_full | Vivianite formation in methane-rich deep-sea sediments from the South China Sea |
| title_fullStr | Vivianite formation in methane-rich deep-sea sediments from the South China Sea |
| title_full_unstemmed | Vivianite formation in methane-rich deep-sea sediments from the South China Sea |
| title_short | Vivianite formation in methane-rich deep-sea sediments from the South China Sea |
| title_sort | vivianite formation in methane rich deep sea sediments from the south china sea |
| url | https://www.biogeosciences.net/15/6329/2018/bg-15-6329-2018.pdf |
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