Abstract
The contribution of bacterial biomass to total particulate organic matter (POM) in the ocean, including exported material, is poorly constrained. To examine potential signatures for the presence and export of bacterioplankton and their detrital remains, here we provide a detailed compound-specific 13C characterization of fatty acids from membrane polar lipids obtained from a water column profile in the Eastern Tropical North Pacific. POM of submicron size (0.2-0.7μm; "X-POM") was sampled and analyzed separately from the size class typically collected as "suspended" POM (0.7-53μm; "L-POM"). The distributions of polar head group classes, specific fatty acid side chains, and natural 13C contents all vary, both between particle size classes and with depth in the water column. In general, the polar lipids in submicron material - and by inference, lipids of bacterial origin - have higher 13C content than polar lipids from larger POM and are equally abundant. Lipid signatures from the photic zone appear to be partially conserved in the suspended pool during transit down the water column. However, bacterial heterotrophy and possibly chemoautotrophy partially overprint these surface signatures. In addition, active metabolisms in the oxygen minimum zone (OMZ) appear to mediate the disaggregation of POM transported from the surface, thus adding complexity to the pathways of mid-water carbon flux and providing additional organic substrates to the OMZ and below. This "substrate injection" may provide important fuel for the denitrification and anammox reactions. Finally, examination of 13C content in polar lipids provides a basis for new interpretation of depth-related variations in δ13C values of bulk suspended POM.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 15-34 |
| Number of pages | 20 |
| Journal | Deep-Sea Research Part I: Oceanographic Research Papers |
| Volume | 85 |
| DOIs | |
| State | Published - Mar 1 2014 |
| Externally published | Yes |
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Keywords
- Bacteria
- Carbon isotopes
- Eastern Tropical North Pacific
- Lipid biomarkers
- Oxygen minimum zone
- Particulate organic matter
ASJC Scopus subject areas
- Oceanography
- Aquatic Science
Cite this
Lipid and 13C signatures of submicron and suspended particulate organic matter in the Eastern Tropical North Pacific : Implications for the contribution of Bacteria. / Close, Hilary; Wakeham, Stuart G.; Pearson, Ann.
In: Deep-Sea Research Part I: Oceanographic Research Papers, Vol. 85, 01.03.2014, p. 15-34.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Lipid and 13C signatures of submicron and suspended particulate organic matter in the Eastern Tropical North Pacific
T2 - Implications for the contribution of Bacteria
AU - Close, Hilary
AU - Wakeham, Stuart G.
AU - Pearson, Ann
PY - 2014/3/1
Y1 - 2014/3/1
N2 - The contribution of bacterial biomass to total particulate organic matter (POM) in the ocean, including exported material, is poorly constrained. To examine potential signatures for the presence and export of bacterioplankton and their detrital remains, here we provide a detailed compound-specific 13C characterization of fatty acids from membrane polar lipids obtained from a water column profile in the Eastern Tropical North Pacific. POM of submicron size (0.2-0.7μm; "X-POM") was sampled and analyzed separately from the size class typically collected as "suspended" POM (0.7-53μm; "L-POM"). The distributions of polar head group classes, specific fatty acid side chains, and natural 13C contents all vary, both between particle size classes and with depth in the water column. In general, the polar lipids in submicron material - and by inference, lipids of bacterial origin - have higher 13C content than polar lipids from larger POM and are equally abundant. Lipid signatures from the photic zone appear to be partially conserved in the suspended pool during transit down the water column. However, bacterial heterotrophy and possibly chemoautotrophy partially overprint these surface signatures. In addition, active metabolisms in the oxygen minimum zone (OMZ) appear to mediate the disaggregation of POM transported from the surface, thus adding complexity to the pathways of mid-water carbon flux and providing additional organic substrates to the OMZ and below. This "substrate injection" may provide important fuel for the denitrification and anammox reactions. Finally, examination of 13C content in polar lipids provides a basis for new interpretation of depth-related variations in δ13C values of bulk suspended POM.
AB - The contribution of bacterial biomass to total particulate organic matter (POM) in the ocean, including exported material, is poorly constrained. To examine potential signatures for the presence and export of bacterioplankton and their detrital remains, here we provide a detailed compound-specific 13C characterization of fatty acids from membrane polar lipids obtained from a water column profile in the Eastern Tropical North Pacific. POM of submicron size (0.2-0.7μm; "X-POM") was sampled and analyzed separately from the size class typically collected as "suspended" POM (0.7-53μm; "L-POM"). The distributions of polar head group classes, specific fatty acid side chains, and natural 13C contents all vary, both between particle size classes and with depth in the water column. In general, the polar lipids in submicron material - and by inference, lipids of bacterial origin - have higher 13C content than polar lipids from larger POM and are equally abundant. Lipid signatures from the photic zone appear to be partially conserved in the suspended pool during transit down the water column. However, bacterial heterotrophy and possibly chemoautotrophy partially overprint these surface signatures. In addition, active metabolisms in the oxygen minimum zone (OMZ) appear to mediate the disaggregation of POM transported from the surface, thus adding complexity to the pathways of mid-water carbon flux and providing additional organic substrates to the OMZ and below. This "substrate injection" may provide important fuel for the denitrification and anammox reactions. Finally, examination of 13C content in polar lipids provides a basis for new interpretation of depth-related variations in δ13C values of bulk suspended POM.
KW - Bacteria
KW - Carbon isotopes
KW - Eastern Tropical North Pacific
KW - Lipid biomarkers
KW - Oxygen minimum zone
KW - Particulate organic matter
UR - http://www.scopus.com/inward/record.url?scp=84891395623&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84891395623&partnerID=8YFLogxK
U2 - 10.1016/j.dsr.2013.11.005
DO - 10.1016/j.dsr.2013.11.005
M3 - Article
VL - 85
SP - 15
EP - 34
JO - Deep-Sea Research Part I: Oceanographic Research Papers
JF - Deep-Sea Research Part I: Oceanographic Research Papers
SN - 0967-0637
ER -