Small pigmented eukaryotes play a major role in carbon cycling in the P‐depleted western subtropical North Atlantic, which may be supported by mixotrophy

We found that in the phosphate (PO4)‐depleted western subtropical North Atlantic Ocean, small‐sized pigmented eukaryotes (P‐Euk; < 5 μm) play a central role in the carbon (C) cycling. Although P‐Euk were only ~ 5% of the microbial phytoplankton cell abundance, they represented at least two thirds...

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Main Authors: Duhamel, Solange, Kim, Eunsoo, Sprung, Ben, Anderson, O. Roger
Format: Article in Journal/Newspaper
Language:English
Published: 2019
Subjects:
Online Access:https://doi.org/10.7916/d8-4p69-zs03
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spelling ftcolumbiauniv:oai:academiccommons.columbia.edu:10.7916/d8-4p69-zs03 2023-05-15T17:29:44+02:00 Small pigmented eukaryotes play a major role in carbon cycling in the P‐depleted western subtropical North Atlantic, which may be supported by mixotrophy Duhamel, Solange Kim, Eunsoo Sprung, Ben Anderson, O. Roger 2019 https://doi.org/10.7916/d8-4p69-zs03 English eng https://doi.org/10.7916/d8-4p69-zs03 Biogeochemistry Chemical oceanography Carbon cycle (Biogeochemistry) Eukaryotic cells Articles 2019 ftcolumbiauniv https://doi.org/10.7916/d8-4p69-zs03 2020-04-04T22:19:50Z We found that in the phosphate (PO4)‐depleted western subtropical North Atlantic Ocean, small‐sized pigmented eukaryotes (P‐Euk; < 5 μm) play a central role in the carbon (C) cycling. Although P‐Euk were only ~ 5% of the microbial phytoplankton cell abundance, they represented at least two thirds of the microbial phytoplankton C biomass and fixed more CO2 than picocyanobacteria, accounting for roughly half of the volumetric CO2 fixation by the microbial phytoplankton, or a third of the total primary production. Cell‐specific PO4 assimilation rates of P‐Euk and nonpigmented eukaryotes (NP‐Euk; < 5 μm) were generally higher than of picocyanobacteria. However, when normalized to biovolumes, picocyanobacteria assimilated roughly four times more PO4 than small eukaryotes, indicating different strategies to cope with PO4 limitation. Our results underline an imbalance in the CO2 : PO4 uptake rate ratios, which may be explained by phagotrophic predation providing mixotrophic protists with their largest source of PO4. 18S rDNA amplicon sequence analyses suggested that P‐Euk was dominated by members of green algae and dinoflagellates, the latter group commonly mixotrophic, whereas marine alveolates were the dominant NP‐Euk. Bacterivory by P‐Euk (0.9 ± 0.3 bacteria P‐Euk−1 h−1) was comparable to values previously measured in the central North Atlantic, indicating that small mixotrophic eukaryotes likely exhibit similar predatory pressure on bacteria. Interestingly, bacterivory rates were reduced when PO4 was added during experimental incubations, indicating that feeding rate by P‐Euk is regulated by PO4 availability. This may be in response to the higher cost associated with assimilating PO4 by phagocytosis compared to osmotrophy. Article in Journal/Newspaper North Atlantic Columbia University: Academic Commons
institution Open Polar
collection Columbia University: Academic Commons
op_collection_id ftcolumbiauniv
language English
topic Biogeochemistry
Chemical oceanography
Carbon cycle (Biogeochemistry)
Eukaryotic cells
spellingShingle Biogeochemistry
Chemical oceanography
Carbon cycle (Biogeochemistry)
Eukaryotic cells
Duhamel, Solange
Kim, Eunsoo
Sprung, Ben
Anderson, O. Roger
Small pigmented eukaryotes play a major role in carbon cycling in the P‐depleted western subtropical North Atlantic, which may be supported by mixotrophy
topic_facet Biogeochemistry
Chemical oceanography
Carbon cycle (Biogeochemistry)
Eukaryotic cells
description We found that in the phosphate (PO4)‐depleted western subtropical North Atlantic Ocean, small‐sized pigmented eukaryotes (P‐Euk; < 5 μm) play a central role in the carbon (C) cycling. Although P‐Euk were only ~ 5% of the microbial phytoplankton cell abundance, they represented at least two thirds of the microbial phytoplankton C biomass and fixed more CO2 than picocyanobacteria, accounting for roughly half of the volumetric CO2 fixation by the microbial phytoplankton, or a third of the total primary production. Cell‐specific PO4 assimilation rates of P‐Euk and nonpigmented eukaryotes (NP‐Euk; < 5 μm) were generally higher than of picocyanobacteria. However, when normalized to biovolumes, picocyanobacteria assimilated roughly four times more PO4 than small eukaryotes, indicating different strategies to cope with PO4 limitation. Our results underline an imbalance in the CO2 : PO4 uptake rate ratios, which may be explained by phagotrophic predation providing mixotrophic protists with their largest source of PO4. 18S rDNA amplicon sequence analyses suggested that P‐Euk was dominated by members of green algae and dinoflagellates, the latter group commonly mixotrophic, whereas marine alveolates were the dominant NP‐Euk. Bacterivory by P‐Euk (0.9 ± 0.3 bacteria P‐Euk−1 h−1) was comparable to values previously measured in the central North Atlantic, indicating that small mixotrophic eukaryotes likely exhibit similar predatory pressure on bacteria. Interestingly, bacterivory rates were reduced when PO4 was added during experimental incubations, indicating that feeding rate by P‐Euk is regulated by PO4 availability. This may be in response to the higher cost associated with assimilating PO4 by phagocytosis compared to osmotrophy.
format Article in Journal/Newspaper
author Duhamel, Solange
Kim, Eunsoo
Sprung, Ben
Anderson, O. Roger
author_facet Duhamel, Solange
Kim, Eunsoo
Sprung, Ben
Anderson, O. Roger
author_sort Duhamel, Solange
title Small pigmented eukaryotes play a major role in carbon cycling in the P‐depleted western subtropical North Atlantic, which may be supported by mixotrophy
title_short Small pigmented eukaryotes play a major role in carbon cycling in the P‐depleted western subtropical North Atlantic, which may be supported by mixotrophy
title_full Small pigmented eukaryotes play a major role in carbon cycling in the P‐depleted western subtropical North Atlantic, which may be supported by mixotrophy
title_fullStr Small pigmented eukaryotes play a major role in carbon cycling in the P‐depleted western subtropical North Atlantic, which may be supported by mixotrophy
title_full_unstemmed Small pigmented eukaryotes play a major role in carbon cycling in the P‐depleted western subtropical North Atlantic, which may be supported by mixotrophy
title_sort small pigmented eukaryotes play a major role in carbon cycling in the p‐depleted western subtropical north atlantic, which may be supported by mixotrophy
publishDate 2019
url https://doi.org/10.7916/d8-4p69-zs03
genre North Atlantic
genre_facet North Atlantic
op_relation https://doi.org/10.7916/d8-4p69-zs03
op_doi https://doi.org/10.7916/d8-4p69-zs03
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