Ammonium is the preferred source of nitrogen for planktonic foraminifer and their dinoflagellate symbionts.
The symbiotic planktonic foraminifera Orbulina universa inhabits open ocean oligotrophic ecosystems where dissolved nutrients are scarce and often limit biological productivity. It has previously been proposed that O. universa meets its nitrogen (N) requirements by preying on zooplankton, and that i...
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ftcdlib:oai:escholarship.org/ark:/13030/qt0134j5wj 2023-05-15T18:00:42+02:00 Ammonium is the preferred source of nitrogen for planktonic foraminifer and their dinoflagellate symbionts. LeKieffre, Charlotte Spero, Howard J Fehrenbacher, Jennifer S Russell, Ann D Ren, Haojia Geslin, Emmanuelle Meibom, Anders 20200620 2020-06-17 application/pdf https://escholarship.org/uc/item/0134j5wj unknown eScholarship, University of California qt0134j5wj https://escholarship.org/uc/item/0134j5wj public Proceedings. Biological sciences, vol 287, iss 1929 Animals Plankton Dinoflagellida Carbon Nitrogen Ammonium Compounds Ecosystem Symbiosis Foraminifera ammonium assimilation ammonium recycling photosymbiosis dinoflagellate symbiosis planktonic foraminifera Biological Sciences Agricultural and Veterinary Sciences Medical and Health Sciences article 2020 ftcdlib 2021-01-24T17:38:05Z The symbiotic planktonic foraminifera Orbulina universa inhabits open ocean oligotrophic ecosystems where dissolved nutrients are scarce and often limit biological productivity. It has previously been proposed that O. universa meets its nitrogen (N) requirements by preying on zooplankton, and that its symbiotic dinoflagellates recycle metabolic 'waste ammonium' for their N pool. However, these conclusions were derived from bulk 15N-enrichment experiments and model calculations, and our understanding of N assimilation and exchange between the foraminifer host cell and its symbiotic dinoflagellates remains poorly constrained. Here, we present data from pulse-chase experiments with 13C-enriched inorganic carbon, 15N-nitrate, and 15N-ammonium, as well as a 13C- and 15N- enriched heterotrophic food source, followed by TEM (transmission electron microscopy) coupled to NanoSIMS (nanoscale secondary ion mass spectrometry) isotopic imaging to visualize and quantify C and N assimilation and translocation in the symbiotic system. High levels of 15N-labelling were observed in the dinoflagellates and in foraminiferal organelles and cytoplasm after incubation with 15N-ammonium, indicating efficient ammonium assimilation. Only weak 15N-assimilation was observed after incubation with 15N-nitrate. Feeding foraminifers with 13C- and 15N-labelled food resulted in dinoflagellates that were labelled with 15N, thereby confirming the transfer of 15N-compounds from the digestive vacuoles of the foraminifer to the symbiotic dinoflagellates, likely through recycling of ammonium. These observations are important for N isotope-based palaeoceanographic reconstructions, as they show that δ15N values recorded in the organic matrix in symbiotic species likely reflect ammonium recycling rather than alternative N sources, such as nitrates. Article in Journal/Newspaper Planktonic foraminifera University of California: eScholarship |
institution |
Open Polar |
collection |
University of California: eScholarship |
op_collection_id |
ftcdlib |
language |
unknown |
topic |
Animals Plankton Dinoflagellida Carbon Nitrogen Ammonium Compounds Ecosystem Symbiosis Foraminifera ammonium assimilation ammonium recycling photosymbiosis dinoflagellate symbiosis planktonic foraminifera Biological Sciences Agricultural and Veterinary Sciences Medical and Health Sciences |
spellingShingle |
Animals Plankton Dinoflagellida Carbon Nitrogen Ammonium Compounds Ecosystem Symbiosis Foraminifera ammonium assimilation ammonium recycling photosymbiosis dinoflagellate symbiosis planktonic foraminifera Biological Sciences Agricultural and Veterinary Sciences Medical and Health Sciences LeKieffre, Charlotte Spero, Howard J Fehrenbacher, Jennifer S Russell, Ann D Ren, Haojia Geslin, Emmanuelle Meibom, Anders Ammonium is the preferred source of nitrogen for planktonic foraminifer and their dinoflagellate symbionts. |
topic_facet |
Animals Plankton Dinoflagellida Carbon Nitrogen Ammonium Compounds Ecosystem Symbiosis Foraminifera ammonium assimilation ammonium recycling photosymbiosis dinoflagellate symbiosis planktonic foraminifera Biological Sciences Agricultural and Veterinary Sciences Medical and Health Sciences |
description |
The symbiotic planktonic foraminifera Orbulina universa inhabits open ocean oligotrophic ecosystems where dissolved nutrients are scarce and often limit biological productivity. It has previously been proposed that O. universa meets its nitrogen (N) requirements by preying on zooplankton, and that its symbiotic dinoflagellates recycle metabolic 'waste ammonium' for their N pool. However, these conclusions were derived from bulk 15N-enrichment experiments and model calculations, and our understanding of N assimilation and exchange between the foraminifer host cell and its symbiotic dinoflagellates remains poorly constrained. Here, we present data from pulse-chase experiments with 13C-enriched inorganic carbon, 15N-nitrate, and 15N-ammonium, as well as a 13C- and 15N- enriched heterotrophic food source, followed by TEM (transmission electron microscopy) coupled to NanoSIMS (nanoscale secondary ion mass spectrometry) isotopic imaging to visualize and quantify C and N assimilation and translocation in the symbiotic system. High levels of 15N-labelling were observed in the dinoflagellates and in foraminiferal organelles and cytoplasm after incubation with 15N-ammonium, indicating efficient ammonium assimilation. Only weak 15N-assimilation was observed after incubation with 15N-nitrate. Feeding foraminifers with 13C- and 15N-labelled food resulted in dinoflagellates that were labelled with 15N, thereby confirming the transfer of 15N-compounds from the digestive vacuoles of the foraminifer to the symbiotic dinoflagellates, likely through recycling of ammonium. These observations are important for N isotope-based palaeoceanographic reconstructions, as they show that δ15N values recorded in the organic matrix in symbiotic species likely reflect ammonium recycling rather than alternative N sources, such as nitrates. |
format |
Article in Journal/Newspaper |
author |
LeKieffre, Charlotte Spero, Howard J Fehrenbacher, Jennifer S Russell, Ann D Ren, Haojia Geslin, Emmanuelle Meibom, Anders |
author_facet |
LeKieffre, Charlotte Spero, Howard J Fehrenbacher, Jennifer S Russell, Ann D Ren, Haojia Geslin, Emmanuelle Meibom, Anders |
author_sort |
LeKieffre, Charlotte |
title |
Ammonium is the preferred source of nitrogen for planktonic foraminifer and their dinoflagellate symbionts. |
title_short |
Ammonium is the preferred source of nitrogen for planktonic foraminifer and their dinoflagellate symbionts. |
title_full |
Ammonium is the preferred source of nitrogen for planktonic foraminifer and their dinoflagellate symbionts. |
title_fullStr |
Ammonium is the preferred source of nitrogen for planktonic foraminifer and their dinoflagellate symbionts. |
title_full_unstemmed |
Ammonium is the preferred source of nitrogen for planktonic foraminifer and their dinoflagellate symbionts. |
title_sort |
ammonium is the preferred source of nitrogen for planktonic foraminifer and their dinoflagellate symbionts. |
publisher |
eScholarship, University of California |
publishDate |
2020 |
url |
https://escholarship.org/uc/item/0134j5wj |
op_coverage |
20200620 |
genre |
Planktonic foraminifera |
genre_facet |
Planktonic foraminifera |
op_source |
Proceedings. Biological sciences, vol 287, iss 1929 |
op_relation |
qt0134j5wj https://escholarship.org/uc/item/0134j5wj |
op_rights |
public |
_version_ |
1766169895394869248 |