Movement of new nitrogen through oceanic food webs: a stable isotope approach
Nitrogen (N) generally limits primary production across large areas of the world's oceans. Allochthonous inputs of N (i.e., "new" N) via N2-fixing organisms (diazotrophs) are crucial for sustaining primary production and are often associated with net export of organic matter (OM) from...
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Georgia Institute of Technology
2009
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Online Access: | http://hdl.handle.net/1853/28151 |
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ftgeorgiatech:oai:repository.gatech.edu:1853/28151 2024-06-02T08:11:19+00:00 Movement of new nitrogen through oceanic food webs: a stable isotope approach Landrum, Jason Paul Montoya, Joseph P. Ellery Ingall Emanuele DiLorenzo Weissburg, Marc Mark Hay Biology 2009-04-06 application/pdf http://hdl.handle.net/1853/28151 unknown Georgia Institute of Technology http://hdl.handle.net/1853/28151 Nitrogen Diazotrophs Zooplankton Isotopes North Atlantic Nitrogen-fixing microorganisms Text Dissertation 2009 ftgeorgiatech 2024-05-06T11:28:20Z Nitrogen (N) generally limits primary production across large areas of the world's oceans. Allochthonous inputs of N (i.e., "new" N) via N2-fixing organisms (diazotrophs) are crucial for sustaining primary production and are often associated with net export of organic matter (OM) from surface waters. Diazotroph N (ND) contribution plays an integral role in supporting oceanic food webs and regulating the flux of OM into and through the oceans (e.g., the biological pump). Stable isotope techniques were used to trace the input and movement of new N through oceanic food webs. Laboratory experiments were performed to determine elemental and isotopic shifts of OM exposed to microbial and metazoan processing. δ15N of OM was typically higher when exposed to microbial communities, with no difference in δ15N of OM between experiments incubated at different temperatures (4°C and 25°C). In separate experiments, shrimp digestion did not alter the δ15N of OM through digestion, but the δ15N of macerated OM was enriched in 15N. Both of these experiments provide insight into the mechanisms driving variations in the δ15N of OM in the world's oceans. To assess the role of diazotrophs in oceanic food webs, we used the distribution of δ15N to quantify the relative ND contribution to suspended particle N (PN) and mesozooplankton N biomass (NZOOP) in the subtropical North Atlantic (STNA). Qualitatively, ND contribution was often high for both PN and NZOOP, with the highest contributions occurring in the mixed layer. Our results also indicate higher ND contribution to both PN and NZOOP in the western portion of the basin than in the east. ND contribution to larger mesozooplankton at depth further suggests that migrating mesozooplankton transport ND out of the mixed layer. Quantitatively, ND trophic transfer efficiency was lower than bulk N trophic transfer efficiency, suggesting low assimilation of ND by mesozooplankton. Overall, we estimated a ND pool turnover time on the order of weeks for our region of study. These findings ... Doctoral or Postdoctoral Thesis North Atlantic Georgia Institute of Technology: SMARTech - Scholarly Materials and Research at Georgia Tech |
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Georgia Institute of Technology: SMARTech - Scholarly Materials and Research at Georgia Tech |
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ftgeorgiatech |
language |
unknown |
topic |
Nitrogen Diazotrophs Zooplankton Isotopes North Atlantic Nitrogen-fixing microorganisms |
spellingShingle |
Nitrogen Diazotrophs Zooplankton Isotopes North Atlantic Nitrogen-fixing microorganisms Landrum, Jason Paul Movement of new nitrogen through oceanic food webs: a stable isotope approach |
topic_facet |
Nitrogen Diazotrophs Zooplankton Isotopes North Atlantic Nitrogen-fixing microorganisms |
description |
Nitrogen (N) generally limits primary production across large areas of the world's oceans. Allochthonous inputs of N (i.e., "new" N) via N2-fixing organisms (diazotrophs) are crucial for sustaining primary production and are often associated with net export of organic matter (OM) from surface waters. Diazotroph N (ND) contribution plays an integral role in supporting oceanic food webs and regulating the flux of OM into and through the oceans (e.g., the biological pump). Stable isotope techniques were used to trace the input and movement of new N through oceanic food webs. Laboratory experiments were performed to determine elemental and isotopic shifts of OM exposed to microbial and metazoan processing. δ15N of OM was typically higher when exposed to microbial communities, with no difference in δ15N of OM between experiments incubated at different temperatures (4°C and 25°C). In separate experiments, shrimp digestion did not alter the δ15N of OM through digestion, but the δ15N of macerated OM was enriched in 15N. Both of these experiments provide insight into the mechanisms driving variations in the δ15N of OM in the world's oceans. To assess the role of diazotrophs in oceanic food webs, we used the distribution of δ15N to quantify the relative ND contribution to suspended particle N (PN) and mesozooplankton N biomass (NZOOP) in the subtropical North Atlantic (STNA). Qualitatively, ND contribution was often high for both PN and NZOOP, with the highest contributions occurring in the mixed layer. Our results also indicate higher ND contribution to both PN and NZOOP in the western portion of the basin than in the east. ND contribution to larger mesozooplankton at depth further suggests that migrating mesozooplankton transport ND out of the mixed layer. Quantitatively, ND trophic transfer efficiency was lower than bulk N trophic transfer efficiency, suggesting low assimilation of ND by mesozooplankton. Overall, we estimated a ND pool turnover time on the order of weeks for our region of study. These findings ... |
author2 |
Montoya, Joseph P. Ellery Ingall Emanuele DiLorenzo Weissburg, Marc Mark Hay Biology |
format |
Doctoral or Postdoctoral Thesis |
author |
Landrum, Jason Paul |
author_facet |
Landrum, Jason Paul |
author_sort |
Landrum, Jason Paul |
title |
Movement of new nitrogen through oceanic food webs: a stable isotope approach |
title_short |
Movement of new nitrogen through oceanic food webs: a stable isotope approach |
title_full |
Movement of new nitrogen through oceanic food webs: a stable isotope approach |
title_fullStr |
Movement of new nitrogen through oceanic food webs: a stable isotope approach |
title_full_unstemmed |
Movement of new nitrogen through oceanic food webs: a stable isotope approach |
title_sort |
movement of new nitrogen through oceanic food webs: a stable isotope approach |
publisher |
Georgia Institute of Technology |
publishDate |
2009 |
url |
http://hdl.handle.net/1853/28151 |
genre |
North Atlantic |
genre_facet |
North Atlantic |
op_relation |
http://hdl.handle.net/1853/28151 |
_version_ |
1800757430526672896 |