Size-specific opal-bound nitrogen isotope measurements in North Pacific sediments
The nitrogen isotope composition of diatom opal (delta N-15(db)) is a valuable recorder of nitrate utilization in the polar surface oceans and a measure of the efficiency of the biological pump. Past down-core records of delta N-15(db) involved the measurement of the biogenic opal fraction up to 150...
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ftunivbasel:oai:edoc.unibas.ch:73045 2023-05-15T15:43:41+02:00 Size-specific opal-bound nitrogen isotope measurements in North Pacific sediments Studer, Anja S. Ellis, Karen K. Oleynik, Sergey Sigman, Daniel M. Haug, Gerald H. 2013 https://edoc.unibas.ch/73045/ https://doi.org/10.1016/j.gca.2013.06.041 unknown Elsevier Studer, Anja S. and Ellis, Karen K. and Oleynik, Sergey and Sigman, Daniel M. and Haug, Gerald H. (2013) Size-specific opal-bound nitrogen isotope measurements in North Pacific sediments. Geochimica et Cosmochimica Acta, 120. pp. 179-194. doi:10.1016/j.gca.2013.06.041 info:isi/000324809000011 urn:ISSN:0016-7037 urn:ISSN:1872-9533 info:eu-repo/semantics/closedAccess Article PeerReviewed 2013 ftunivbasel https://doi.org/10.1016/j.gca.2013.06.041 2023-03-05T07:23:32Z The nitrogen isotope composition of diatom opal (delta N-15(db)) is a valuable recorder of nitrate utilization in the polar surface oceans and a measure of the efficiency of the biological pump. Past down-core records of delta N-15(db) involved the measurement of the biogenic opal fraction up to 150 mu m in size, which should represent the bulk of the preserved diatoms but may also include non-diatom opal such as radiolaria and sponge spicules. In this study, the opal from subarctic Pacific and Bering Sea sediments from the Holocene back to the last glacial was separated into different size fractions to measure their individual delta N-15. We found a general trend of decreasing delta N-15 with increasing size at all sites and through time. Microscopic investigation of smear slides and image area analysis of microphotographs of the analyzed opal revealed that the larger size fractions contained greater proportions of sponge spicules and radiolaria. Manual isolation and measurement of the sponge spicules showed that they have a very low delta N-15 (similar to -11 parts per thousand). Ultrasonication during sample preparation caused greater spicule and radiolaria contamination due to fragmentation of these relatively large fossils, leading to a dramatic delta N-15(db) decrease with increasing size and lower delta N-15(db) across all size fractions in sonicated versus non-sonicated samples. Nevertheless, these contaminants were also present albeit less abundant in the various size fractions of samples separated without sonication, and these samples also showed a delta N-15(db) decrease with increasing size. Simple isotope mass-balance calculations of Holocene Bering Sea sediments indicate that most of the delta N-15(db) variations among the larger size fractions can be explained by the relative abundance of low-delta N-15 sponge spicules in each fraction. However, some of the size fraction delta N-15 differences in the downcore records require a different explanation. Both diatom inter-or intra-species effects are ... Article in Journal/Newspaper Bering Sea Subarctic University of Basel: edoc Bering Sea Pacific Geochimica et Cosmochimica Acta 120 179 194 |
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University of Basel: edoc |
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ftunivbasel |
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unknown |
description |
The nitrogen isotope composition of diatom opal (delta N-15(db)) is a valuable recorder of nitrate utilization in the polar surface oceans and a measure of the efficiency of the biological pump. Past down-core records of delta N-15(db) involved the measurement of the biogenic opal fraction up to 150 mu m in size, which should represent the bulk of the preserved diatoms but may also include non-diatom opal such as radiolaria and sponge spicules. In this study, the opal from subarctic Pacific and Bering Sea sediments from the Holocene back to the last glacial was separated into different size fractions to measure their individual delta N-15. We found a general trend of decreasing delta N-15 with increasing size at all sites and through time. Microscopic investigation of smear slides and image area analysis of microphotographs of the analyzed opal revealed that the larger size fractions contained greater proportions of sponge spicules and radiolaria. Manual isolation and measurement of the sponge spicules showed that they have a very low delta N-15 (similar to -11 parts per thousand). Ultrasonication during sample preparation caused greater spicule and radiolaria contamination due to fragmentation of these relatively large fossils, leading to a dramatic delta N-15(db) decrease with increasing size and lower delta N-15(db) across all size fractions in sonicated versus non-sonicated samples. Nevertheless, these contaminants were also present albeit less abundant in the various size fractions of samples separated without sonication, and these samples also showed a delta N-15(db) decrease with increasing size. Simple isotope mass-balance calculations of Holocene Bering Sea sediments indicate that most of the delta N-15(db) variations among the larger size fractions can be explained by the relative abundance of low-delta N-15 sponge spicules in each fraction. However, some of the size fraction delta N-15 differences in the downcore records require a different explanation. Both diatom inter-or intra-species effects are ... |
format |
Article in Journal/Newspaper |
author |
Studer, Anja S. Ellis, Karen K. Oleynik, Sergey Sigman, Daniel M. Haug, Gerald H. |
spellingShingle |
Studer, Anja S. Ellis, Karen K. Oleynik, Sergey Sigman, Daniel M. Haug, Gerald H. Size-specific opal-bound nitrogen isotope measurements in North Pacific sediments |
author_facet |
Studer, Anja S. Ellis, Karen K. Oleynik, Sergey Sigman, Daniel M. Haug, Gerald H. |
author_sort |
Studer, Anja S. |
title |
Size-specific opal-bound nitrogen isotope measurements in North Pacific sediments |
title_short |
Size-specific opal-bound nitrogen isotope measurements in North Pacific sediments |
title_full |
Size-specific opal-bound nitrogen isotope measurements in North Pacific sediments |
title_fullStr |
Size-specific opal-bound nitrogen isotope measurements in North Pacific sediments |
title_full_unstemmed |
Size-specific opal-bound nitrogen isotope measurements in North Pacific sediments |
title_sort |
size-specific opal-bound nitrogen isotope measurements in north pacific sediments |
publisher |
Elsevier |
publishDate |
2013 |
url |
https://edoc.unibas.ch/73045/ https://doi.org/10.1016/j.gca.2013.06.041 |
geographic |
Bering Sea Pacific |
geographic_facet |
Bering Sea Pacific |
genre |
Bering Sea Subarctic |
genre_facet |
Bering Sea Subarctic |
op_relation |
Studer, Anja S. and Ellis, Karen K. and Oleynik, Sergey and Sigman, Daniel M. and Haug, Gerald H. (2013) Size-specific opal-bound nitrogen isotope measurements in North Pacific sediments. Geochimica et Cosmochimica Acta, 120. pp. 179-194. doi:10.1016/j.gca.2013.06.041 info:isi/000324809000011 urn:ISSN:0016-7037 urn:ISSN:1872-9533 |
op_rights |
info:eu-repo/semantics/closedAccess |
op_doi |
https://doi.org/10.1016/j.gca.2013.06.041 |
container_title |
Geochimica et Cosmochimica Acta |
container_volume |
120 |
container_start_page |
179 |
op_container_end_page |
194 |
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1766377877715025920 |