Intact polar lipids in the water column of the eastern tropical North Pacific: abundance and structural variety of non-phosphorus lipids

Abstract. Intact polar lipids (IPLs) are the main building blocks of cellular membranes and contain chemotaxonomic, ecophysiological and metabolic information, making them valuable biomarkers in microbial ecology and biogeochemistry. This study investigates IPLs in suspended particulate matter (SPM) in the water column of the eastern tropical North Pacific Ocean (ETNP), one of the most extensive open-ocean oxygen minimum zones (OMZs) in the world, with strong gradients of nutrients, temperature and redox conditions. A wide structural variety in polar lipid head-group composition and core structures exists along physical and geochemical gradients within the water column, from the oxygenated photic zone to the aphotic OMZ. We use this structural diversity in IPLs to evaluate the ecology and ecophysiological adaptations that affect organisms inhabiting the water column, especially the mid-depth OMZ in the context of biogeochemical cycles. Diacylglycerol phospholipids are present at all depths, but exhibit the highest relative abundance and compositional variety (including mixed acyl/ether core structures) in the upper and core OMZ where prokaryotic biomass was enriched. Surface ocean SPM is dominated by diacylglycerol glycolipids that are found in photosynthetic membranes. These and other glycolipids with varying core structures composed of ceramides and hydroxylated fatty acids are also detected with varying relative abundances in the OMZ and deep oxycline, signifying additional non-phototrophic bacterial sources for these lipids. Betaine lipids (with zero or multiple hydroxylations in the core structures) that are typically assigned to microalgae are found throughout the water column down to the deep oxycline but do not show a depth-related trend in relative abundance. Archaeal IPLs comprised of glycosidic and mixed glycosidic-phosphatidic glycerol dibiphytanyl glycerol tetraethers (GDGTs) are most abundant in the upper OMZ, where nitrate maxima point to ammonium oxidation but increase in relative abundance in the core OMZ and deep oxycline. The presence of non-phosphorus “substitute” lipids within the OMZ suggest that the indigenous microbes might be phosphorus limited (P starved) at ambient phosphate concentrations of 1 to 3.5 µM, although specific microbial sources for many of these lipids still remain unknown.

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Diversity of intact polar lipids in the oxygen minimum zone of the Eastern Tropical North Pacific: Biogeochemical implications of non-phosphorus lipids

10.5194/bg-2018-119 ◽

2018 ◽

Author(s):

Florence Schubotz ◽

Sitan Xie ◽

Julius S. Lipp ◽

Kai-Uwe Hinrichs ◽

Stuart G. Wakeham

Keyword(s):

Microbial Ecology ◽

Water Column ◽

Relative Abundance ◽

North Pacific ◽

Building Blocks ◽

Polar Lipids ◽

Ammonium Oxidation ◽

The Core ◽

Intact Polar Lipids ◽

Oxygen Minimum

Abstract. Intact polar lipids (IPLs) are the main building blocks of cellular membranes and contain chemotaxonomic, ecophysiologic and metabolic information, which makes them valuable biomarkers in microbial ecology and biogeochemistry. This study investigates the IPL distribution in suspended particulate matter (SPM) in the water column of the Eastern Tropical North Pacific Ocean (ETNP), an area characterized by one of the most extensive open ocean oxygen minimum zones (OMZ) in the world with strong gradients of nutrients, temperature and redox conditions. A wide structural variety in polar lipid head group composition and core structures exists along physical and geochemical gradients within the OMZ. Our goal is to use this structural diversity in IPLs to evaluate the microbial ecology and ecophysiological adaptations that affect organisms inhabiting the OMZ in the context of biogeochemical cycles. Diacylglycerol phospholipids are present at all depths, but exhibit highest relative abundance and compositional variety (including mixed acyl/ether core structures) in the upper and core OMZ where prokaryotic biomass was enriched. Surface ocean SPM is dominated by diacylglycerol glycolipids that are typical lipid components of photosynthetic membranes. These and other glycolipids with varying core structures composed of ceramides and hydroxylated fatty acids are also detected with varying relative abundances in the OMZ and deep oxycline, signifying additional non-phototrophic bacterial sources for these lipids. Similarly, betaine lipids (with none or multiple hydroxylations in the core structures) that are typically assigned to microalgae are found throughout the water column down to the deep oxycline but do not show a depth-related trend in relative abundance. Archaeal IPLs comprised of glycosidic and mixed glycosidic-phosphatidic glycerol dibiphytanyl glycerol tetraethers (GDGTs) are most abundant in the upper OMZ where nitrate maxima point to ammonium oxidation, but increase in relative abundance in the core OMZ and deep oxycline. The presence of abundant non-phosphorus lipids within the OMZ suggests that the indigenous microbes might be phosphorus limited at phosphate concentrations of 1 to 3.5 µM. It remains unclear if the detected amino and glycolipids indeed function as substitutes for phospholipid in these oxygen-depleted environments as microbial sources for many of these lipids still remain unknown.

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

Biogeosciences ◽

10.5194/bg-12-4725-2015 ◽

2015 ◽

Vol 12 (15) ◽

pp. 4725-4737 ◽

Cited By ~ 12

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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Intact polar lipids of Thaumarchaeota and anammox bacteria as indicators of N-cycling in the Eastern Tropical North Pacific oxygen deficient zone

Biogeosciences Discussions ◽

10.5194/bgd-12-4833-2015 ◽

2015 ◽

Vol 12 (6) ◽

pp. 4833-4864 ◽

Cited By ~ 2

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, either as competition or cooperation.

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Nitrite oxidation in the upper water column and oxygen minimum zone of the eastern tropical North Pacific Ocean

The ISME Journal ◽

10.1038/ismej.2013.96 ◽

2013 ◽

Vol 7 (11) ◽

pp. 2192-2205 ◽

Cited By ~ 60

Author(s):

J Michael Beman ◽

Joy Leilei Shih ◽

Brian N Popp

Keyword(s):

Pacific Ocean ◽

Water Column ◽

North Pacific ◽

North Pacific Ocean ◽

Oxygen Minimum Zone ◽

Nitrite Oxidation ◽

Minimum Zone ◽

Oxygen Minimum

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Time of Maximum Late Wisconsin Glaciation, West Coast of Canada

Quaternary Research ◽

10.1016/0033-5894(90)90041-i ◽

1990 ◽

Vol 34 (3) ◽

pp. 282-295 ◽

Cited By ~ 96

Author(s):

Bertrand Blaise ◽

John J. Clague ◽

Rolf W. Mathewes

Keyword(s):

West Coast ◽

North Pacific ◽

Deep Sea ◽

North Pacific Ocean ◽

Ice Sheet ◽

Late Glacial ◽

Western Margin ◽

The Core ◽

Queen Charlotte Islands ◽

Cordilleran Ice Sheet

AbstractNew data from a deep-sea core in the eastern North Pacific Ocean indicate that the western margin of the Late Wisconsin Cordilleran Ice Sheet began to retreat from its maximum position after 15,600 yr B.P. Ice-rafted detritus is present in the core below the 15,600 yr B.P. level and was deposited while lobes of the Cordilleran Ice Sheet advanced across the continental shelf in Queen Charlotte Sound, Hecate Strait, and Dixon Entrance. The core data are complemented by stratigraphic evidence and radiocarbon ages from Quaternary exposures bordering Hecate Strait and Dixon Entrance. These indicate that piedmont lobes reached the east and north shores of Graham Island (part of the Queen Charlotte Islands) between about 23,000 and 21,000 yr B.P. Sometime thereafter, but before 15,000–16,000 yr B.P., these glaciers achieved their greatest Late Wisconsin extent. Radiocarbon ages of late-glacial and postglacial sediments from Queen Charlotte Sound, Hecate Strait, and adjacent land areas show that deglaciation began in these areas before 15,000 yr B.P. and that the shelf was completely free of ice by 13,000 yr B.P.

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