Organic Phases in Bivalve (Arctica Islandica) Shells: Their Bulk and Amino Acid Nitrogen Stable Isotope Compositions
Abstract The stable nitrogen isotope composition of bivalve shell organics serves as a proxy for nitrogen fluxes in modern and past ecosystems. An essential prerequisite to reconstruct environmental variables from δ15N values of bivalve shells is to understand if pristine isotope signals can be retr...
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ftdoajarticles:oai:doaj.org/article:7680633854054b4f84b2482ca09fd976 2024-09-15T17:54:28+00:00 Organic Phases in Bivalve (Arctica Islandica) Shells: Their Bulk and Amino Acid Nitrogen Stable Isotope Compositions Qian Huang Oluwatoosin B. A. Agbaje Martina Conti Bernd R. Schöne 2023-10-01T00:00:00Z https://doi.org/10.1029/2023GC011147 https://doaj.org/article/7680633854054b4f84b2482ca09fd976 EN eng Wiley https://doi.org/10.1029/2023GC011147 https://doaj.org/toc/1525-2027 1525-2027 doi:10.1029/2023GC011147 https://doaj.org/article/7680633854054b4f84b2482ca09fd976 Geochemistry, Geophysics, Geosystems, Vol 24, Iss 10, Pp n/a-n/a (2023) nitrogen isotope composition amino acids bivalve shells pretreatment protocols Geophysics. Cosmic physics QC801-809 Geology QE1-996.5 article 2023 ftdoajarticles https://doi.org/10.1029/2023GC011147 2024-08-05T17:49:50Z Abstract The stable nitrogen isotope composition of bivalve shell organics serves as a proxy for nitrogen fluxes in modern and past ecosystems. An essential prerequisite to reconstruct environmental variables from δ15N values of bivalve shells is to understand if pristine isotope signals can be retrieved from shell organics after sample pretreatment. δ15N analyses of fossil shells should be limited to the intra‐crystalline organic matrix (intra‐OM), which is trapped within biomineral units and less likely contaminated or diagenetically overprinted than inter‐crystalline organics (inter‐OM). However, it remains unclear whether the different shell organic phases (insoluble/soluble inter‐OM, intra‐OM) are isotopically distinct and whether δ15N values of intra‐OM agree with those of bulk organic matter. These questions were tackled by applying different solvents (H2O, HCl, H2O2, NaOCl) to homogenized shell powder of a modern Arctica islandica. Milli‐Q water did not alter bulk δ15N values indicating the dissolution of the inter‐OM was negligible. Acid‐extracted intra‐OM exhibited a larger isotope variation within replicates and showed a minor but significant fractionation in bulk δ15N values related to the loss of acid‐soluble components. Compared to H2O2, NaOCl oxidative treatment was more effective in cleaning inter‐OM and produced reliable bulk and amino acid (AA)‐specific δ15N data of intra‐OM. Furthermore, differences in the relative abundance and δ15N values of individual AAs suggested that the N isotope composition is not uniform within shells, and the N‐bearing content and AA composition differ between organic phases. Future studies should test the capability of bulk and CSIA‐AA δ15N proxies in fossil shells as paleoenvironmental archives. Article in Journal/Newspaper Arctica islandica Directory of Open Access Journals: DOAJ Articles Geochemistry, Geophysics, Geosystems 24 10 |
institution |
Open Polar |
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Directory of Open Access Journals: DOAJ Articles |
op_collection_id |
ftdoajarticles |
language |
English |
topic |
nitrogen isotope composition amino acids bivalve shells pretreatment protocols Geophysics. Cosmic physics QC801-809 Geology QE1-996.5 |
spellingShingle |
nitrogen isotope composition amino acids bivalve shells pretreatment protocols Geophysics. Cosmic physics QC801-809 Geology QE1-996.5 Qian Huang Oluwatoosin B. A. Agbaje Martina Conti Bernd R. Schöne Organic Phases in Bivalve (Arctica Islandica) Shells: Their Bulk and Amino Acid Nitrogen Stable Isotope Compositions |
topic_facet |
nitrogen isotope composition amino acids bivalve shells pretreatment protocols Geophysics. Cosmic physics QC801-809 Geology QE1-996.5 |
description |
Abstract The stable nitrogen isotope composition of bivalve shell organics serves as a proxy for nitrogen fluxes in modern and past ecosystems. An essential prerequisite to reconstruct environmental variables from δ15N values of bivalve shells is to understand if pristine isotope signals can be retrieved from shell organics after sample pretreatment. δ15N analyses of fossil shells should be limited to the intra‐crystalline organic matrix (intra‐OM), which is trapped within biomineral units and less likely contaminated or diagenetically overprinted than inter‐crystalline organics (inter‐OM). However, it remains unclear whether the different shell organic phases (insoluble/soluble inter‐OM, intra‐OM) are isotopically distinct and whether δ15N values of intra‐OM agree with those of bulk organic matter. These questions were tackled by applying different solvents (H2O, HCl, H2O2, NaOCl) to homogenized shell powder of a modern Arctica islandica. Milli‐Q water did not alter bulk δ15N values indicating the dissolution of the inter‐OM was negligible. Acid‐extracted intra‐OM exhibited a larger isotope variation within replicates and showed a minor but significant fractionation in bulk δ15N values related to the loss of acid‐soluble components. Compared to H2O2, NaOCl oxidative treatment was more effective in cleaning inter‐OM and produced reliable bulk and amino acid (AA)‐specific δ15N data of intra‐OM. Furthermore, differences in the relative abundance and δ15N values of individual AAs suggested that the N isotope composition is not uniform within shells, and the N‐bearing content and AA composition differ between organic phases. Future studies should test the capability of bulk and CSIA‐AA δ15N proxies in fossil shells as paleoenvironmental archives. |
format |
Article in Journal/Newspaper |
author |
Qian Huang Oluwatoosin B. A. Agbaje Martina Conti Bernd R. Schöne |
author_facet |
Qian Huang Oluwatoosin B. A. Agbaje Martina Conti Bernd R. Schöne |
author_sort |
Qian Huang |
title |
Organic Phases in Bivalve (Arctica Islandica) Shells: Their Bulk and Amino Acid Nitrogen Stable Isotope Compositions |
title_short |
Organic Phases in Bivalve (Arctica Islandica) Shells: Their Bulk and Amino Acid Nitrogen Stable Isotope Compositions |
title_full |
Organic Phases in Bivalve (Arctica Islandica) Shells: Their Bulk and Amino Acid Nitrogen Stable Isotope Compositions |
title_fullStr |
Organic Phases in Bivalve (Arctica Islandica) Shells: Their Bulk and Amino Acid Nitrogen Stable Isotope Compositions |
title_full_unstemmed |
Organic Phases in Bivalve (Arctica Islandica) Shells: Their Bulk and Amino Acid Nitrogen Stable Isotope Compositions |
title_sort |
organic phases in bivalve (arctica islandica) shells: their bulk and amino acid nitrogen stable isotope compositions |
publisher |
Wiley |
publishDate |
2023 |
url |
https://doi.org/10.1029/2023GC011147 https://doaj.org/article/7680633854054b4f84b2482ca09fd976 |
genre |
Arctica islandica |
genre_facet |
Arctica islandica |
op_source |
Geochemistry, Geophysics, Geosystems, Vol 24, Iss 10, Pp n/a-n/a (2023) |
op_relation |
https://doi.org/10.1029/2023GC011147 https://doaj.org/toc/1525-2027 1525-2027 doi:10.1029/2023GC011147 https://doaj.org/article/7680633854054b4f84b2482ca09fd976 |
op_doi |
https://doi.org/10.1029/2023GC011147 |
container_title |
Geochemistry, Geophysics, Geosystems |
container_volume |
24 |
container_issue |
10 |
_version_ |
1810430791680786432 |