scholarly journals Seasonal and multi-annual variation in the abundance of isoprenoid GDGT membrane lipids and their producers in the water column of a meromictic equatorial crater lake (Lake Chala, East Africa)

2021 ◽  
Vol 273 ◽  
pp. 107263
Author(s):  
A.J. Baxter ◽  
L.G.J. van Bree ◽  
F. Peterse ◽  
E.C. Hopmans ◽  
L. Villanueva ◽  
...  
Keyword(s):  
Water Column ◽  
East Africa ◽  
Annual Variation ◽  
Crater Lake ◽  
Membrane Lipids

scholarly journals Influence of ammonia oxidation rate on thaumarchaeal lipid composition and the TEX86 temperature proxy

2016 ◽  
Vol 113 (28) ◽  
pp. 7762-7767 ◽  
Author(s):  
Sarah J. Hurley ◽  
Felix J. Elling ◽  
Martin Könneke ◽  
Carolyn Buchwald ◽  
Scott D. Wankel ◽  
...  
Keyword(s):  
Water Column ◽  
Oxidation Rate ◽  
Nutrient Dynamics ◽  
Ammonia Oxidation ◽  
Membrane Lipids ◽  
Reducing Power ◽  
Archaeal Community ◽  
Surface Mixed Layer ◽  
Culture Methods ◽  
Ammonia Oxidation Rate

Archaeal membrane lipids known as glycerol dibiphytanyl glycerol tetraethers (GDGTs) are the basis of the TEX86 paleotemperature proxy. Because GDGTs preserved in marine sediments are thought to originate mainly from planktonic, ammonia-oxidizing Thaumarchaeota, the basis of the correlation between TEX86 and sea surface temperature (SST) remains unresolved: How does TEX86 predict surface temperatures, when maximum thaumarchaeal activity occurs below the surface mixed layer and TEX86 does not covary with in situ growth temperatures? Here we used isothermal studies of the model thaumarchaeon Nitrosopumilus maritimus SCM1 to investigate how GDGT composition changes in response to ammonia oxidation rate. We used continuous culture methods to avoid potential confounding variables that can be associated with experiments in batch cultures. The results show that the ring index scales inversely (R2 = 0.82) with ammonia oxidation rate (ϕ), indicating that GDGT cyclization depends on available reducing power. Correspondingly, the TEX86 ratio decreases by an equivalent of 5.4 °C of calculated temperature over a 5.5 fmol·cell−1·d−1 increase in ϕ. This finding reconciles other recent experiments that have identified growth stage and oxygen availability as variables affecting TEX86. Depth profiles from the marine water column show minimum TEX86 values at the depth of maximum nitrification rates, consistent with our chemostat results. Our findings suggest that the TEX86 signal exported from the water column is influenced by the dynamics of ammonia oxidation. Thus, the global TEX86–SST calibration potentially represents a composite of regional correlations based on nutrient dynamics and global correlations based on archaeal community composition and temperature.

scholarly journals Chemoautotrophy and anoxygenic photosynthesis within the water column of a large meromictic tropical lake (Lake Kivu, East Africa)

2016 ◽  
Vol 61 (4) ◽  
pp. 1424-1437 ◽  
Author(s):  
Cédric Morana ◽  
Fleur A. E. Roland ◽  
Sean A. Crowe ◽  
Marc Llirós ◽  
Alberto V. Borges ◽  
...  
Keyword(s):  
Water Column ◽  
East Africa ◽  
Tropical Lake ◽  
Anoxygenic Photosynthesis ◽  
Lake Kivu

scholarly journals Seasonal variability and sources of in situ brGDGT production in a permanently stratified African crater lake

2020 ◽  
Vol 17 (21) ◽  
pp. 5443-5463
Author(s):  
Loes G. J. van Bree ◽  
Francien Peterse ◽  
Allix J. Baxter ◽  
Wannes De Crop ◽  
Sigrid van Grinsven ◽  
...  
Keyword(s):  
Bacterial Community ◽  
Water Column ◽  
Crater Lake ◽  
Rrna Gene ◽  
Climate History ◽  
Depth Profiles ◽  
Settling Particles ◽  
Environmental Controls ◽  
Lipid Biomarker

Abstract. Lake sediments are important archives of continental climate history, and their lipid biomarker content can be exploited to reconstruct paleoenvironmental conditions. Branched glycerol dialkyl glycerol tetraethers (brGDGTs) are bacterial membrane lipids widely used in paleoclimate studies to reconstruct past temperature. However, major gaps still exist in our understanding of the environmental controls on in situ (i.e. aquatic) production in lake systems. In Lake Chala, a permanently stratified tropical crater lake in East Africa, we determined the concentrations and fractional abundances of individual brGDGTs along depth profiles of suspended particulate matter collected monthly from September 2013 to January 2015 and in settling particles collected monthly at 35 m water depth from August 2010 to January 2015 and compared these brGDGT distributions with those in surficial lake bottom sediments and catchment soils. We find that brGDGTs are primarily produced within the water column and that their concentrations and distributions vary greatly with depth and over time. Comparison with concentration–depth profiles of the monthly distribution and abundance of bacterial taxa, based on 16S rRNA gene amplicon sequencing and quantification, indicates that Acidobacteria are likely not the main producers of brGDGTs in Lake Chala. Shallowing of the oxic–anoxic boundary during seasonal episodes of strong water column stratification promoted production of specific brGDGTs in the anoxic zone. BrGDGT distributions in the water column do not consistently relate with temperature, pH, or dissolved-oxygen concentration but do respond to transitions between episodes of strong stratification and deep (but partial) lake mixing, as does the aquatic bacterial community. Hence, the general link between brGDGT distributions and temperature in brGDGT-based paleothermometry is more likely driven by a change in bacterial community composition than by membrane adaptation of specific members of the bacterial community to changing environmental conditions. Although temperature is not the principal driver of distributional changes in aquatic brGDGTs in this system, at least not during the 17-month study period, abundance-weighted and time-integrated averages of brGDGT fractional abundance in the 53-month time series of settling particles reveal systematic variability over longer timescales that indirectly relates to temperature. Thus, although we do not as yet fully understand the drivers of modern-day brGDGT fluxes and distributions in Lake Chala, our data do support the application of brGDGT paleothermometry to time-integrated archives such as sediments. Highlights. BrGDGTs in the tropical African lake Chala are produced in situ. Acidobacteria are not the dominant source of aquatic brGDGTs. Stratification and mixing drive aquatic brGDGT production and their signature.

Crater Lake revisited: Concentration changes in water column radionuclides, 1967 to 1981

1983 ◽  
Vol 88 (C7) ◽  
pp. 4531 ◽  
Author(s):  
Herbert L. Volchok ◽  
Vaughan T. Bowen ◽  
William R. Clark ◽  
Lary R. Ball
Keyword(s):  
Water Column ◽  
Crater Lake ◽  
Concentration Changes

Reduced sulfur and iron species in anoxic water column of meromictic crater Lake Pavin (Massif Central, France)

2009 ◽  
Vol 266 (3-4) ◽  
pp. 311-317 ◽  
Author(s):  
Elvira Bura-Nakić ◽  
Eric Viollier ◽  
Didier Jézéquel ◽  
Alassane Thiam ◽  
Irena Ciglenečki
Keyword(s):  
Water Column ◽  
Crater Lake ◽  
Iron Species ◽  
Massif Central ◽  
Anoxic Water ◽  
Reduced Sulfur ◽  
Lake Pavin

scholarly journals Provenance of tetraether membrane lipids in a large temperate lake (Loch Lomond, UK): implications for GDGT-based palaeothermometry

2014 ◽  
Vol 11 (3) ◽  
pp. 4187-4250 ◽  
Author(s):  
L. K. Buckles ◽  
J. W. H. Weijers ◽  
X.-M. Tran ◽  
S. Waldron ◽  
J. S. Sinninghe Damsté
Keyword(s):  
Lake Sediments ◽  
Water Column ◽  
Membrane Lipids ◽  
Lacustrine Sediments ◽  
Small Rivers ◽  
The South ◽  
Factors Affecting ◽  
The North ◽  
Loch Lomond

Abstract. The application of glycerol dialkyl glycerol tetraether (GDGT)-based palaeoenvironmental proxies, such as the BIT index, TEX86 and the MBT/CBT palaeothermometer, has lately been expanded to lacustrine sediments. Given recent research identifying the production of branched, bacterial GDGTs (brGDGTs) within lakes, it is necessary to ascertain the effect of this lacustrine production on GDGT-based proxies. This study profiles a temperate, monomictic lake (Loch Lomond, UK), analysing labile intact polar GDGT lipids (IPLs) and resilient core GDGT lipids (CLs) in catchment soils, small tributary rivers, lake water and lake sediments. Loch Lomond consists of two basins bisected by the Highland Boundary Fault, resulting in a mesotrophic to oligotrophic gradient from south to north. The north basin is fjord-like, while the south basin is shallow with a lowland catchment. Besides abundant influxes of allochthonous soil and peat-derived (CL) brGDGTs, brGDGTs are produced in a variety of settings in Loch Lomond. Rather than integrating a scattered soil signal, there is some evidence that small rivers may contribute to the brGDGT pool through addition of brGDGTs produced in situ in these streams. 300 days of settling particles and water column profiles of suspended particulate matter (SPM; March and September 2011) reveal brGDGT production throughout the water column, with (IPL and CL) brGDGT distributions varying by basin. In lake sediments, in situ brGDGT production affects the distributions of sedimentary brGDGTs despite high soil and peat-derived organic matter influxes from the catchment. MBT/CBT-derived mean annual air temperature (MAAT) estimates from soil, river and lake sediments vary widely. A strong bias towards higher MAATs in the south and lower MAATs in the north basin further complicates the application of the proxy. These results emphasise that caution must be exercised when applying the MBT/CBT palaeothermometer to individual lakes in which the use of the proxy has not been validated and therefore the factors affecting its application are not well understood. Despite elevated BIT indices, (partly) due to in situ brGDGT production, reliable TEX86 lake surface temperature (LST) estimates were obtained from SPM with BIT indices up to 0.9 but containing abundant crenarchaeol. Lower north basin sediments yielded accurate LST estimates but require further evaluation to properly constrain the application of the TEX86 proxy.

scholarly journals Intact polar lipids of Thaumarchaeota and anammox bacteria as indicators of N cycling in the eastern tropical North Pacific oxygen-deficient zone

2015 ◽  
Vol 12 (15) ◽  
pp. 4725-4737 ◽  
Author(s):  
M. Sollai ◽  
E. C. Hopmans ◽  
S. Schouten ◽  
R. G. Keil ◽  
J. S. Sinninghe Damsté
Keyword(s):  
Water Column ◽  
North Pacific ◽  
Membrane Lipids ◽  
Open Water ◽  
Open Ocean ◽  
Polar Lipids ◽  
Anammox Bacteria ◽  
N Budget ◽  
Intact Polar Lipids ◽  
Microbial Groups

Abstract. In the last decade our understanding of the marine nitrogen cycle has improved considerably thanks to the discovery of two novel groups of microorganisms: ammonia-oxidizing archaea (AOA) and anaerobic ammonia-oxidizing (anammox) bacteria. Both groups are important in oxygen-deficient zones (ODZs), where they substantially affect the marine N budget. These two groups of microbes are also well known for producing specific membrane lipids, which can be used as biomarkers to trace their presence in the environment. We investigated the occurrence and distribution of AOA and anammox bacteria in the water column of the eastern tropical North Pacific (ETNP) ODZ, one of the most prominent ODZs worldwide. Suspended particulate matter (SPM) was collected at different depths of the water column in high resolution, at both a coastal and an open-ocean setting. The SPM was analyzed for AOA- and anammox bacteria-specific intact polar lipids (IPLs), i.e., hexose-phosphohexose (HPH)-crenarchaeol and phosphatidylcholine (PC)-monoether ladderane. Comparison with oxygen profiles reveals that both the microbial groups are able to thrive at low (< 1 μM) concentrations of oxygen. Our results indicate a clear niche segregation of AOA and anammox bacteria in the coastal waters of the ETNP but a partial overlap of the two niches of these microbial species in the open-water setting. The latter distribution suggests the potential for an interaction between the two microbial groups at the open-ocean site, although the nature of this hypothetical interaction (i.e., either competition or cooperation) remains unclear.

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