The vertical distribution of Thaumarchaeota in the water column of Lake Malawi inferred from core and intact polar tetraether lipids

Dervla Meegan Kumar; Martijn Woltering; Ellen C. Hopmans; Jaap S. Sinninghe Damsté; Stefan Schouten; Josef P. Werne

doi:10.1016/j.orggeochem.2019.03.004

The vertical distribution of Thaumarchaeota in the water column of Lake Malawi inferred from core and intact polar tetraether lipids

Dervla Meegan Kumar
, Martijn Woltering
, Ellen C. Hopmans
, Jaap S. Sinninghe Damsté
, Stefan Schouten
, Josef P. Werne^*

^*Corresponding author for this work

Research output: Contribution to journal › Article › Academic › peer-review

Abstract

Several long paleoclimate records generated from Lake Malawi sediments rely on an assumption that the TEX₈₆ paleothermometer reflects annual mean lake surface temperatures. Thaumarchaeota, the producers of the isoprenoid glycerol dialkyl glycerol tetraether (iGDGT) lipids that are the basis of the TEX₈₆ proxy, can occupy a wide range of habitats in the upper water column of lacustrine systems, so it is crucial to specifically constrain the ecology of Thaumarchaeota in Lake Malawi to properly interpret its sedimentary TEX₈₆ record. To investigate the spatial and vertical distribution of Thaumarchaeotal iGDGT production in Lake Malawi, suspended particulate matter (SPM) was collected from the upper water column (>300 m) at three sites spanning the north, central, and south basins of the lake and analyzed for intact polar (IPL) and core (CL) iGDGT lipid abundances. Samples were collected in January during the austral summer when the lake is strongly stratified. Concentrations of the most labile IPL, hexose-phosphohexose (HPH)-crenarchaeol, were greatest just below the deep chlorophyll maximum at ∼50 m water depth in the deeper north and central basins and ∼30 m in the shallow south basin. Maximum CL concentrations occur below the maximum HPH-crenarchaeol concentrations and therefore possibly reflect the accumulation of recently produced IPL GDGT degradation products. If the export of CLs to the sediments is dominated by this CL pool, sedimentary TEX₈₆ would reflect Thaumarchaeota living within the thermocline during the stratified season and therefore may have a cool bias rather than reflecting true surface water temperatures. An increase in abundances of GDGT-2, crenarchaeol isomer, and monohexose (MH)-crenarchaeol at ∼150–200 m suggests that a secondary Thaumarchaeotal population, likely Group I.1b Thaumarchaeota, inhabits the subsurface water column near the anoxic-suboxic boundary. Total production of iGDGTs by this group appears to be much lower than the surface-dwelling clade, but its imprint on sedimentary TEX₈₆ is unknown. An analysis of iGDGT production in the water column throughout the annual cycle is needed to resolve the timing and magnitude of export of CLs to the sediments from these two Thaumarchaeotal populations.

Original language	English
Pages (from-to)	37-49
Number of pages	13
Journal	Organic Geochemistry
Volume	132
DOIs	https://doi.org/10.1016/j.orggeochem.2019.03.004
Publication status	Published - Jun 2019

Funding

We give special thanks to Maxon Ngochera for his huge contributions in both organizing and assisting with this fieldwork on Lake Malawi. We also thank T.C. Johnson and R. Hecky for their help in organizing this research cruise on Lake Malawi, and T.C. Johnson additionally for providing the bathymetric data. We would like to thank the captain and crew of the R.V. Ndumduma, M. Berke, M. Maccuiane and A. Abbott for help they provided before, during, and after the cruise on Lake Malawi. We thank J. Ossebaar at the Royal NIOZ for their analytical assistance with IPLs. We thank two anonymous reviewers, Associate Editor P. Meyers, and the Editor-in-Chief J.K. Volkman for comments that improved this manuscript. This work was funded by grants from the National Geographic Society Committee for Research and Exploration (# 8098-06 ) and University of Minnesota Grant-in-Aid of Research # 20607 to JPW, and the University of Minnesota Office of International Programs to JPW and REH. A portion of this work was prepared while JPW was on leave at the Centre for Water Research, University of Western Australia, Crawley, WA, Australia and the WA-Organic and Isotope Geochemistry Centre, Curtin University of Technology, Bentley, WA, Australia. ECH, SS and JSSD are supported by the Netherlands Earth System Science Center (NESSC) funded by the Dutch ministry of Education, Culture and Science. Appendix A

Keywords

GDGT
Intact polar lipids
Lake Malawi
TEX
Thaumarchaeota

Access to Document

10.1016/j.orggeochem.2019.03.004

Vertical distribution of ThaumarchaeotaFinal published version, 1.04 MBLicence: Taverne

Cite this

@article{c3b2f42ededb4ba48a192b441c321105,

title = "The vertical distribution of Thaumarchaeota in the water column of Lake Malawi inferred from core and intact polar tetraether lipids",

abstract = "Several long paleoclimate records generated from Lake Malawi sediments rely on an assumption that the TEX86 paleothermometer reflects annual mean lake surface temperatures. Thaumarchaeota, the producers of the isoprenoid glycerol dialkyl glycerol tetraether (iGDGT) lipids that are the basis of the TEX86 proxy, can occupy a wide range of habitats in the upper water column of lacustrine systems, so it is crucial to specifically constrain the ecology of Thaumarchaeota in Lake Malawi to properly interpret its sedimentary TEX86 record. To investigate the spatial and vertical distribution of Thaumarchaeotal iGDGT production in Lake Malawi, suspended particulate matter (SPM) was collected from the upper water column (>300 m) at three sites spanning the north, central, and south basins of the lake and analyzed for intact polar (IPL) and core (CL) iGDGT lipid abundances. Samples were collected in January during the austral summer when the lake is strongly stratified. Concentrations of the most labile IPL, hexose-phosphohexose (HPH)-crenarchaeol, were greatest just below the deep chlorophyll maximum at ∼50 m water depth in the deeper north and central basins and ∼30 m in the shallow south basin. Maximum CL concentrations occur below the maximum HPH-crenarchaeol concentrations and therefore possibly reflect the accumulation of recently produced IPL GDGT degradation products. If the export of CLs to the sediments is dominated by this CL pool, sedimentary TEX86 would reflect Thaumarchaeota living within the thermocline during the stratified season and therefore may have a cool bias rather than reflecting true surface water temperatures. An increase in abundances of GDGT-2, crenarchaeol isomer, and monohexose (MH)-crenarchaeol at ∼150–200 m suggests that a secondary Thaumarchaeotal population, likely Group I.1b Thaumarchaeota, inhabits the subsurface water column near the anoxic-suboxic boundary. Total production of iGDGTs by this group appears to be much lower than the surface-dwelling clade, but its imprint on sedimentary TEX86 is unknown. An analysis of iGDGT production in the water column throughout the annual cycle is needed to resolve the timing and magnitude of export of CLs to the sediments from these two Thaumarchaeotal populations.",

keywords = "GDGT, Intact polar lipids, Lake Malawi, TEX, Thaumarchaeota",

author = "Kumar, \{Dervla Meegan\} and Martijn Woltering and Hopmans, \{Ellen C.\} and \{Sinninghe Damst{\'e}\}, \{Jaap S.\} and Stefan Schouten and Werne, \{Josef P.\}",

year = "2019",

month = jun,

doi = "10.1016/j.orggeochem.2019.03.004",

language = "English",

volume = "132",

pages = "37--49",

journal = "Organic Geochemistry",

issn = "0146-6380",

publisher = "Elsevier Ltd",

}

TY - JOUR

T1 - The vertical distribution of Thaumarchaeota in the water column of Lake Malawi inferred from core and intact polar tetraether lipids

AU - Kumar, Dervla Meegan

AU - Woltering, Martijn

AU - Hopmans, Ellen C.

AU - Sinninghe Damsté, Jaap S.

AU - Schouten, Stefan

AU - Werne, Josef P.

PY - 2019/6

Y1 - 2019/6

N2 - Several long paleoclimate records generated from Lake Malawi sediments rely on an assumption that the TEX86 paleothermometer reflects annual mean lake surface temperatures. Thaumarchaeota, the producers of the isoprenoid glycerol dialkyl glycerol tetraether (iGDGT) lipids that are the basis of the TEX86 proxy, can occupy a wide range of habitats in the upper water column of lacustrine systems, so it is crucial to specifically constrain the ecology of Thaumarchaeota in Lake Malawi to properly interpret its sedimentary TEX86 record. To investigate the spatial and vertical distribution of Thaumarchaeotal iGDGT production in Lake Malawi, suspended particulate matter (SPM) was collected from the upper water column (>300 m) at three sites spanning the north, central, and south basins of the lake and analyzed for intact polar (IPL) and core (CL) iGDGT lipid abundances. Samples were collected in January during the austral summer when the lake is strongly stratified. Concentrations of the most labile IPL, hexose-phosphohexose (HPH)-crenarchaeol, were greatest just below the deep chlorophyll maximum at ∼50 m water depth in the deeper north and central basins and ∼30 m in the shallow south basin. Maximum CL concentrations occur below the maximum HPH-crenarchaeol concentrations and therefore possibly reflect the accumulation of recently produced IPL GDGT degradation products. If the export of CLs to the sediments is dominated by this CL pool, sedimentary TEX86 would reflect Thaumarchaeota living within the thermocline during the stratified season and therefore may have a cool bias rather than reflecting true surface water temperatures. An increase in abundances of GDGT-2, crenarchaeol isomer, and monohexose (MH)-crenarchaeol at ∼150–200 m suggests that a secondary Thaumarchaeotal population, likely Group I.1b Thaumarchaeota, inhabits the subsurface water column near the anoxic-suboxic boundary. Total production of iGDGTs by this group appears to be much lower than the surface-dwelling clade, but its imprint on sedimentary TEX86 is unknown. An analysis of iGDGT production in the water column throughout the annual cycle is needed to resolve the timing and magnitude of export of CLs to the sediments from these two Thaumarchaeotal populations.

AB - Several long paleoclimate records generated from Lake Malawi sediments rely on an assumption that the TEX86 paleothermometer reflects annual mean lake surface temperatures. Thaumarchaeota, the producers of the isoprenoid glycerol dialkyl glycerol tetraether (iGDGT) lipids that are the basis of the TEX86 proxy, can occupy a wide range of habitats in the upper water column of lacustrine systems, so it is crucial to specifically constrain the ecology of Thaumarchaeota in Lake Malawi to properly interpret its sedimentary TEX86 record. To investigate the spatial and vertical distribution of Thaumarchaeotal iGDGT production in Lake Malawi, suspended particulate matter (SPM) was collected from the upper water column (>300 m) at three sites spanning the north, central, and south basins of the lake and analyzed for intact polar (IPL) and core (CL) iGDGT lipid abundances. Samples were collected in January during the austral summer when the lake is strongly stratified. Concentrations of the most labile IPL, hexose-phosphohexose (HPH)-crenarchaeol, were greatest just below the deep chlorophyll maximum at ∼50 m water depth in the deeper north and central basins and ∼30 m in the shallow south basin. Maximum CL concentrations occur below the maximum HPH-crenarchaeol concentrations and therefore possibly reflect the accumulation of recently produced IPL GDGT degradation products. If the export of CLs to the sediments is dominated by this CL pool, sedimentary TEX86 would reflect Thaumarchaeota living within the thermocline during the stratified season and therefore may have a cool bias rather than reflecting true surface water temperatures. An increase in abundances of GDGT-2, crenarchaeol isomer, and monohexose (MH)-crenarchaeol at ∼150–200 m suggests that a secondary Thaumarchaeotal population, likely Group I.1b Thaumarchaeota, inhabits the subsurface water column near the anoxic-suboxic boundary. Total production of iGDGTs by this group appears to be much lower than the surface-dwelling clade, but its imprint on sedimentary TEX86 is unknown. An analysis of iGDGT production in the water column throughout the annual cycle is needed to resolve the timing and magnitude of export of CLs to the sediments from these two Thaumarchaeotal populations.

KW - GDGT

KW - Intact polar lipids

KW - Lake Malawi

KW - TEX

KW - Thaumarchaeota

UR - https://www.scopus.com/pages/publications/85064324859

U2 - 10.1016/j.orggeochem.2019.03.004

DO - 10.1016/j.orggeochem.2019.03.004

M3 - Article

AN - SCOPUS:85064324859

SN - 0146-6380

VL - 132

SP - 37

EP - 49

JO - Organic Geochemistry

JF - Organic Geochemistry

ER -

The vertical distribution of Thaumarchaeota in the water column of Lake Malawi inferred from core and intact polar tetraether lipids

Abstract

Funding

Keywords

Access to Document

Other files and links

Fingerprint

Cite this