scholarly journals Intact polar lipids in the hadal seabed of the Atacama Trench point to lateral sediment transport and in situ production as key sources of labile organic matter

2021 ◽  
Author(s):  
Edgart Flores ◽  
Sebastian I. Cantarero ◽  
Paula Ruiz-Fernández ◽  
Nadia Dildar ◽  
Matthias Zabel ◽  
...  
Keyword(s):  
High Pressure ◽  
Organic Matter ◽  
Low Temperature ◽  
Unsaturated Fatty Acids ◽  
Euphotic Zone ◽  
Polar Lipids ◽  
Physiological Adaptation ◽  
Labile Organic Matter ◽  
Intact Polar Lipids

Abstract. Elevated concentrations of organic matter are found in sediments of hadal trenches relative to those found in the abyssal seabed, but the origin of such biological material remains elusive. Here, we report the composition and distribution of cell membrane intact polar lipids (IPLs) in surface sediments around the deepest points of the Atacama Trench and adjacent bathyal depths to assess and constrain the sources of labile organic matter in the hadal seabed. Multiscale bootstrap resampling of IPLs’ structural diversity and abundance indicates distinct lipid signatures in the sediments of the Atacama Trench that are more closely related to those found in bathyal sediments than to those previously reported for the upper ocean water column in the region. While the overall number of unique IPL structures in hadal sediments is limited and they contribute a small fraction of the total IPL pool, they include a high contribution of phospholipids with mono- and di-unsaturated fatty acids that are not associated with photoautotrophic sources. The diversity of labile IPLs in hadal sediments of the Atacama Trench suggests the presence of in situ microbial production and biomass that resembles traits of physiological adaptation to high pressure and low temperature, and/or the transport of labile organic matter from shallower sediment. We argue that the export of the most labile lipid component of the organic matter pool from the euphotic zone and the overlying oxygen minimum zone into the hadal sediments is neglectable. Our results contribute to the understanding of the mechanisms that control the delivery of labile organic matter to this extreme deep-sea ecosystem, whereas they provide insights into some potential physiological adaptation of the in situ microbial community to high pressure and low temperature through lipid remodeling.

Intact Polar Lipids in Surface Sediments of The Atacama Trench Point to In Situ Dominant Sources of Labile Organic Matter in the Hadal Seabed

2021 ◽  
Author(s):  
Edgart Flores ◽  
Sebastian Cantarero ◽  
Paula Ruiz-Fernández ◽  
Nadia Dildar ◽  
Matthias Zabel ◽  
...  
Keyword(s):  
Organic Matter ◽  
Surface Sediments ◽  
Polar Lipids ◽  
Labile Organic Matter ◽  
Intact Polar Lipids

scholarly journals Lipid biomarkers in Holocene and glacial sediments from ancient Lake Ohrid (Macedonia, Albania)

2010 ◽  
Vol 7 (11) ◽  
pp. 3473-3489 ◽  
Author(s):  
J. Holtvoeth ◽  
H. Vogel ◽  
B. Wagner ◽  
G. A. Wolff
Keyword(s):  
Organic Matter ◽  
Lipid Biomarkers ◽  
Lake Ohrid ◽  
Labile Organic Matter ◽  
Glacial Sediments ◽  
Plant Matter ◽  
Lipid Biomarker ◽  
First Results ◽  
Near Shore

Abstract. Organic matter preserved in Lake Ohrid sediments originates from aquatic and terrestrial sources. Its variable composition reflects climate-controlled changes in the lake basin's hydrology and related organic matter export, i.e. changes in primary productivity, terrestrial plant matter input and soil erosion. Here, we present first results from lipid biomarker investigations of Lake Ohrid sediments from two near-shore settings: site Lz1120 near the southern shore, with low-lying lands nearby and probably influenced by river discharge, and site Co1202 which is close to the steep eastern slopes. Variable proportions of terrestrial n-alkanoic acids and n-alkanols as well as compositional changes of ω-hydroxy acids document differences in soil organic matter supply between the sites and during different climate stages (glacial, Holocene, 8.2 ka cooling event). Changes in the vegetation cover are suggested by changes in the dominant chain length of terrestrial n-alkanols. Effective microbial degradation of labile organic matter and in situ contribution of organic matter derived from the microbes themselves are both evident in the sediments. We found evidence for anoxic conditions within the photic zone by detecting epicholestanol and tetrahymanol from sulphur-oxidising phototrophic bacteria and bacterivorous ciliates and for the influence of a settled human community from the occurrence of coprostanol, a biomarker for human and animal faeces (pigs, sheep, goats), in an early Holocene sample. This study illustrates the potential of lipid biomarkers for future environmental reconstructions using one of Europe's oldest continental climate archives, Lake Ohrid.

Monounsaturated but Not Polyunsaturated Fatty Acids Are Required for Growth of the Deep-Sea BacteriumPhotobacterium profundum SS9 at High Pressure and Low Temperature

1999 ◽  
Vol 65 (4) ◽  
pp. 1710-1720 ◽  
Author(s):  
Eric E. Allen ◽  
Daniel Facciotti ◽  
Douglas H. Bartlett
Keyword(s):  
Fatty Acids ◽  
High Pressure ◽  
Fatty Acid ◽  
Low Temperature ◽  
Mutant Strain ◽  
Deep Sea ◽  
High Pressures ◽  
Unsaturated Fatty Acids ◽  
Temperature Sensitive ◽  
Pressure Sensitive

ABSTRACT There is considerable evidence correlating the production of increased proportions of membrane unsaturated fatty acids (UFAs) with bacterial growth at low temperatures or high pressures. In order to assess the importance of UFAs to microbial growth under these conditions, the effects of conditions altering UFA levels in the psychrotolerant piezophilic deep-sea bacterium Photobacterium profundum SS9 were investigated. The fatty acids produced byP. profundum SS9 grown at various temperatures and pressures were characterized, and differences in fatty acid composition as a function of phase growth, and between inner and outer membranes, were noted. P. profundum SS9 was found to exhibit enhanced proportions of both monounsaturated (MUFAs) and polyunsaturated (PUFAs) fatty acids when grown at a decreased temperature or elevated pressure. Treatment of cells with cerulenin inhibited MUFA but not PUFA synthesis and led to a decreased growth rate and yield at low temperature and high pressure. In addition, oleic acid-auxotrophic mutants were isolated. One of these mutants, strain EA3, was deficient in the production of MUFAs and was both low-temperature sensitive and high-pressure sensitive in the absence of exogenous 18:1 fatty acid. Another mutant, strain EA2, produced little MUFA but elevated levels of the PUFA species eicosapentaenoic acid (EPA; 20:5n-3). This mutant grew slowly but was not low-temperature sensitive or high-pressure sensitive. Finally, reverse genetics was employed to construct a mutant unable to produce EPA. This mutant, strain EA10, was also not low-temperature sensitive or high-pressure sensitive. The significance of these results to the understanding of the role of UFAs in growth under low-temperature or high-pressure conditions is discussed.

High-pressure developments for resonant X-ray scattering experiments at I16

2020 ◽  
Vol 27 (2) ◽  
pp. 351-359
Author(s):  
I. Povedano ◽  
A. Bombardi ◽  
D. G. Porter ◽  
M. Burt ◽  
S. Green ◽  
...  
Keyword(s):  
High Pressure ◽  
Low Temperature ◽  
The Body ◽  
X Ray ◽  
X Ray Scattering ◽  
Scattering Geometry ◽  
Diamond Anvil ◽  
Membrane Cell ◽  
Ray Scattering

An experimental setup to perform high-pressure resonant X-ray scattering (RXS) experiments at low temperature on I16 at Diamond Light Source is presented. The setup consists of a membrane-driven diamond anvil cell, a panoramic dome and an optical system that allows pressure to be measured in situ using the ruby fluorescence method. The membrane cell, inspired by the Merrill–Bassett design, presents an asymmetric layout in order to operate in a back-scattering geometry, with a panoramic aperture of 100° in the top and a bottom half dedicated to the regulation and measurement of pressure. It is specially designed to be mounted on the cold finger of a 4 K closed-cycle cryostat and actuated at low-temperature by pumping helium into the gas membrane. The main parts of the body are machined from a CuBe alloy (BERYLCO 25) and, when assembled, it presents an approximate height of 20–21 mm and fits into a 57 mm diameter. This system allows different materials to be probed using RXS in a range of temperatures between 30 and 300 K and has been tested up to 20 GPa using anvils with a culet diameter of 500 µm under quasi-cryogenic conditions. Detailed descriptions of different parts of the setup, operation and the developed methodology are provided here, along with some preliminary experimental results.

scholarly journals The high-pressure and low-temperature structural behaviour of 2,2,2-trifluoroethanol

CrystEngComm ◽  
2019 ◽  
Vol 21 (30) ◽  
pp. 4501-4506
Author(s):  
S. A. Barnett ◽  
D. R. Allan
Keyword(s):  
High Pressure ◽  
Low Temperature ◽  
Crystal Structures ◽  
Structural Behaviour

Polymorphic crystal structures have been determined for 2,2,2-trifluoroethanol by using the in situ crystallography techniques of high pressure and cryo-cooling.

In situ Raman spectroscopy of low-temperature/high-pressure transformations of H2O

2007 ◽  
Vol 126 (17) ◽  
pp. 174505 ◽  
Author(s):  
Yukihiro Yoshimura ◽  
Sarah T. Stewart ◽  
Ho-kwang Mao ◽  
Russell J. Hemley
Keyword(s):  
Raman Spectroscopy ◽  
High Pressure ◽  
Low Temperature ◽  
In Situ Raman Spectroscopy ◽  
In Situ Raman

scholarly journals Measuring rates of gross photosynthesis and net community production in cryoconite holes: a comparison of field methods

2010 ◽  
Vol 51 (56) ◽  
pp. 153-162 ◽  
Author(s):  
J. Telling ◽  
A.M. Anesio ◽  
J. Hawkings ◽  
M. Tranter ◽  
J.L. Wadham ◽  
...  
Keyword(s):  
Organic Matter ◽  
Molar Ratio ◽  
Net Community Production ◽  
Field Methods ◽  
Labile Organic Matter ◽  
Gross Photosynthesis ◽  
Ice Melt ◽  
Order Of Magnitude ◽  
Community Production

AbstractPhotosynthesis by microbes on the surfaces of glaciers and ice sheets has the potential to fix carbon, alter the albedo of ice surfaces via the production of organic matter and so enhance ice melt. It could also be important for supplying labile organic matter and nutrients to in situ and downstream ecosystems. This study compares in situ 24 hour incubation methods for measuring rates of gross photosynthesis, respiration and net community production (NCP) in cryoconite holes on three Svalbard valley glaciers. Rates of gross photosynthesis and respiration measured by the ΔCO2method were closely balanced, resulting in rates of NCP close to the detection limit (mean of –1.3 μg C g−1d–1) consistent with previous measurements in Arctic cryoconite holes. This suggests that organic matter within cryoconite holes may be derived largely from allochthonous sources. The molar ratio of ΔO2to ΔCO2in incubations gave mean respiratory and photosynthetic quotients of 0.80 ± 0.17 (1 × SD) and 1.24 ± 0.20 (1 × SD), respectively. The 14C method typically underestimated rates of gross photosynthesis (ΔCO2method) by more than one order of magnitude and measured a rate closer to NCP.

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