Revised brGDGT fractional abundances and warm-season temperatures strengthen relationships between brGDGTs and environmental variables

2021 ◽  
Author(s):  
Jonathan H. Raberg ◽  
Aria Blumm ◽  
David J. Harning ◽  
Sarah E. Crump ◽  
Greg de Wet ◽  
...  
Keyword(s):  
Lake Sediments ◽  
Lake Water ◽  
Environmental Variables ◽  
Surface Sediments ◽  
Membrane Lipids ◽  
Warm Season ◽  
Important Variable ◽  
Water Conductivity ◽  
Temperature Conductivity ◽  
Air Temperatures

<p>Branched glycerol dialkyl glycerol tetraethers (brGDGTs) are an important tool for reconstructing terrestrial paleotemperatures from lake sediments. In addition to temperature, however, the distribution of these bacterial membrane lipids is influenced by other environmental variables such as pH, conductivity, and dissolved oxygen. Furthermore, though most brGDGT calibrations are performed against mean annual air temperature (MAT), there is considerable evidence that their distributions are more closely tied to warm-season conditions. Here, we present a new method for analyzing brGDGT data that deconvolves the influences of temperature, conductivity, and pH. Additionally, we measure brGDGT distributions in surface sediments from 43 high-latitude lakes with low MAT and high seasonality. In combination with a globally compiled lake sediment dataset, these samples show a clear warm-season bias in brGDGT-derived temperatures. They also show lake water conductivity to be the second-most important variable in controlling brGDGT distributions. We use the compiled dataset and new fractional abundances to generate brGDGT calibrations for warm-season air temperatures and lake water conductivity and pH for use in lake sediments globally.</p>

scholarly journals Revised fractional abundances and warm-season temperatures substantially improve brGDGT calibrations in lake sediments

2021 ◽  
Author(s):  
Jonathan H. Raberg ◽  
David J. Harning ◽  
Sarah E. Crump ◽  
Greg de Wet ◽  
Aria Blumm ◽  
...  
Keyword(s):  
Lake Sediments ◽  
Lake Sediment ◽  
Membrane Lipids ◽  
Warm Season ◽  
Environmental Parameters ◽  
Structural Diversity ◽  
Temperature Conductivity ◽  
Advantages And Disadvantages ◽  
Natural Logarithm ◽  
Air Temperatures

Abstract. Distributions of branched glycerol dialkyl glycerol tetraethers (brGDGTs) are frequently employed for reconstructing terrestrial paleotemperatures from lake sediment archives. Although brGDGTs are globally ubiquitous, the microbial producers of these membrane lipids remain unknown, precluding a full understanding of the ways in which environmental parameters control their production and distribution. Here, we advance this understanding in three ways. First, we present 43 new high-latitude lake sites characterized by low mean annual air temperatures (MATs) and high seasonality, filling an important gap in the global dataset. Second, we introduce a new approach for analyzing brGDGT data in which compound fractional abundances (FAs) are calculated within structural groups based on methylation number, methylation position, and cyclization number. Finally, we perform linear and nonlinear regressions of the resulting FAs against a suite of environmental parameters in a compiled global lake sediment dataset (n = 182). We find that our approach deconvolves temperature, conductivity, and pH trends in brGDGTs without increasing calibration errors from the standard approach. We also find that it reveals novel patterns in brGDGT distributions and provides a methodology for investigating the biological underpinnings of their structural diversity. Warm-season temperature indices outperformed MAT in our regressions, with Months Above Freezing yielding the highest-performing model (adjusted R2 = 0.91, RMSE = 1.97 °C, n = 182). The natural logarithm of conductivity had the second-strongest relationship to brGDGT distributions (adjusted R2 = 0.83, RMSE = 0.66, n = 143), notably outperforming pH in our dataset (adjusted R2 = 0.73, RMSE = 0.57, n = 154) and providing a potential new proxy for paleohydrology applications. We recommend these calibrations for use in lake sediments globally, including at high latitudes, and detail the advantages and disadvantages of each.

scholarly journals Revised fractional abundances and warm-season temperatures substantially improve brGDGT calibrations in lake sediments

2021 ◽  
Vol 18 (12) ◽  
pp. 3579-3603
Author(s):  
Jonathan H. Raberg ◽  
David J. Harning ◽  
Sarah E. Crump ◽  
Greg de Wet ◽  
Aria Blumm ◽  
...  
Keyword(s):  
Lake Sediments ◽  
Lake Sediment ◽  
Membrane Lipids ◽  
Warm Season ◽  
Environmental Parameters ◽  
Structural Diversity ◽  
Temperature Conductivity ◽  
Advantages And Disadvantages ◽  
Natural Logarithm ◽  
Air Temperatures

Abstract. Distributions of branched glycerol dialkyl glycerol tetraethers (brGDGTs) are frequently employed for reconstructing terrestrial paleotemperatures from lake sediment archives. Although brGDGTs are globally ubiquitous, the microbial producers of these membrane lipids remain unknown, precluding a full understanding of the ways in which environmental parameters control their production and distribution. Here, we advance this understanding in three ways. First, we present 43 new high-latitude lake sites characterized by low mean annual air temperatures (MATs) and high seasonality, filling an important gap in the global dataset. Second, we introduce a new approach for analyzing brGDGT data in which compound fractional abundances (FAs) are calculated within structural groups based on methylation number, methylation position, and cyclization number. Finally, we perform linear and nonlinear regressions of the resulting FAs against a suite of environmental parameters in a compiled global lake sediment dataset (n = 182). We find that our approach deconvolves temperature, conductivity, and pH trends in brGDGTs without increasing calibration errors from the standard approach. We also find that it reveals novel patterns in brGDGT distributions and provides a methodology for investigating the biological underpinnings of their structural diversity. Warm-season temperature indices outperformed MAT in our regressions, with the mean temperature of months above freezing yielding the highest-performing model (adjusted R2 = 0.91, RMSE = 1.97 ∘C, n = 182). The natural logarithm of conductivity had the second-strongest relationship to brGDGT distributions (adjusted R2 = 0.83, RMSE = 0.66, n = 143), notably outperforming pH in our dataset (adjusted R2 = 0.73, RMSE = 0.57, n = 154) and providing a potential new proxy for paleohydrology applications. We recommend these calibrations for use in lake sediments globally, including at high latitudes, and detail the advantages and disadvantages of each.

scholarly journals Traces of sunlight in the organic matter biogeochemistry of two shallow subarctic lakes

2021 ◽  
Author(s):  
Marttiina V. Rantala ◽  
Carsten Meyer-Jacob ◽  
E. Henriikka Kivilä ◽  
Tomi P. Luoto ◽  
Antti. E. K. Ojala ◽  
...  
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Lake Sediments ◽  
Lake Water ◽  
Human Impacts ◽  
Global Environmental Change ◽  
Carbon Export ◽  
Subarctic Lakes ◽  
Carbon Regulation ◽  
In Situ Experiments

AbstractGlobal environmental change alters the production, terrestrial export, and photodegradation of organic carbon in northern lakes. Sedimentary biogeochemical records can provide a unique means to understand the nature of these changes over long time scales, where observational data fall short. We deployed in situ experiments on two shallow subarctic lakes with contrasting light regimes; a clear tundra lake and a dark woodland lake, to first investigate the photochemical transformation of carbon and nitrogen elemental (C/N ratio) and isotope (δ13C, δ15N) composition in lake water particulate organic matter (POM) for downcore inferences. We then explored elemental, isotopic, and spectral (inferred lake water total organic carbon [TOC] and sediment chlorophyll a [CHLa]) fingerprints in the lake sediments to trace changes in aquatic production, terrestrial inputs and photodegradation before and after profound human impacts on the global carbon cycle prompted by industrialization. POM pool in both lakes displayed tentative evidence of UV photoreactivity, reflected as increasing δ13C and decreasing C/N values. Through time, the tundra lake sediments traced subtle shifts in primary production, while the woodland lake carried signals of changing terrestrial contributions, indicating shifts in terrestrial carbon export but possibly also photodegradation rates. Under global human impact, both lakes irrespective of their distinct carbon regimes displayed evidence of increased productivity but no conspicuous signs of increased terrestrial influence. Overall, sediment biogeochemistry can integrate a wealth of information on carbon regulation in northern lakes, while our results also point to the importance of considering the entire spectrum of photobiogeochemical fingerprints in sedimentary studies.

Assessment of nutrients and heavy metals in the surface sediments of the artificially lake water reservoir Karla, Thessaly, Greece

2014 ◽  
Vol 73 (8) ◽  
pp. 4483-4493 ◽  
Author(s):  
Konstantinos Skordas ◽  
Efstratios Kelepertzis ◽  
Dimitrios Kosmidis ◽  
Panagiota Panagiotaki ◽  
Dimitrios Vafidis
Keyword(s):  
Heavy Metals ◽  
Lake Water ◽  
Surface Sediments ◽  
Water Reservoir

Metabarcoding of modern sedimentary DNA from the Tibetan Plateau and Siberia as a training dataset for vegetation reconstructions

2021 ◽  
Author(s):  
Weihan Jia ◽  
Kathleen Stoof-Leichsenring ◽  
Sisi Liu ◽  
Kai Li ◽  
Sichao Huang ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Lake Sediments ◽  
Plant Diversity ◽  
Lake Water ◽  
Aquatic Plant ◽  
Freshwater Ecosystems ◽  
The Tibetan Plateau ◽  
Plant Dna ◽  
Continental Scale ◽  
Dna Metabarcoding

<p>Lake sedimentary DNA (<em>sed</em>DNA) is an established tool to trace past changes in vegetation composition and plant diversity. However, little is known about the relationships between sedimentary plant DNA and modern vegetational and environmental conditions. In this study, we investigate i) the relationships between the preservation of sedimentary plant DNA and environmental variables, ii) the modern analogue of ancient plant DNA assemblages archived in lake sediments, and iii) the usability of sedimentary plant DNA for characterization of terrestrial and aquatic plant composition and diversity based on a large dataset of PCR-amplified plant DNA data retrieved from 259 lake surface sediments from the Tibetan Plateau and Siberia. Our results indicate the following: i) Lake-water electrical conductivity and pH are the most important variables for the preservation of plant DNA in lake sediments. We expect the best preservation conditions for sedimentary plant DNA in small deep lakes characterized by high water conductivities (≥100 μS cm<sup>-1</sup>) and neutral to slightly alkaline pH conditions (7–9). ii) Plant DNA metabarcoding is promising for palaeovegetation reconstruction in high mountain regions, where shifts in vegetation are solely captured by the <em>sed</em>DNA-based analogue matching and fossil pollen generally has poor modern analogues. However, the biases in the representation of some taxa could lead to poor analogue conditions. iii) Plant DNA metabarcoding is a reliable proxy to reflect modern vegetation types and climate characteristics at a sub-continental scale. However, the resolution of the <em>trn</em>L P6 loop marker, the incompleteness of the reference library, and the extent of <em>sed</em>DNA preservation are still the main limitations of this method. iv) Plant DNA metabarcoding is a suitable proxy to recover modern aquatic plant diversity, which is mostly affected by July temperature and lake-water conductivity. Ongoing warming might decrease macrophyte richness in the Tibetan Plateau and Siberia, and ultimately threaten the health of these important freshwater ecosystems. To conclude, sedimentary plant DNA presents a high correlation with modern vegetation and may therefore be an important proxy for reconstruction of past vegetation.</p>

scholarly journals Environmental Variables of the Seti Gandaki River Basin Pokhara, Nepal

2018 ◽  
Vol 22 (2) ◽  
pp. 129-139 ◽  
Author(s):  
Kishor Kumar Pokharel ◽  
Khadga Bahadur Basnet ◽  
Trilok Chandra Majupuria ◽  
Chitra Bahadur Baniya
Keyword(s):  
Water Temperature ◽  
River Basin ◽  
Environmental Variables ◽  
Temporal Variations ◽  
Total Alkalinity ◽  
Urban Site ◽  
Water Conductivity ◽  
Free Carbon Dioxide ◽  
Spatio Temporal ◽  
Carbon Dioxide Co2

Present paper focuses on the spatio-temporal variations and correlations among the environmental variables of the Seti Gandaki River basin, Pokhara, Nepal. A total of five sites, three along the river and two in tributaries were selected for this study. Water sampling was done fortnightly for environmental variables following standard methods during July 2011 to June 2012. Mean and standard deviation of the environmental variables revealed that the depth (0.9 ± 0.3), pH (8 ± 0.4), total phosphates (PO4) (0.10 ± 0.03) and nitrates (NO3) (0.13 ± 0.04) were normally variable among the sites. But the discharge (40.00 ± 37.00), width (32.30 ± 13.00), turbidity (81.40 ± 51.00), transparency (29.10 ± 15.00), conductivity (166.00 ± 80.00), water temperature (18.00 ±4.00), dissolved oxygen (DO) (8.00 ± 2.00), free carbon dioxide (CO2) (7.00 ± 2.00) and total alkalinity (98.00 ± 22.00) varied among sites equally. Correlation coefficient between the sites and environmental variables revealed that sites were found significantly correlated with water conductivity (r2 = 0.6), DO (r2 = -0.52), and free CO2 (r2 = 0.6); depth of water with width (r2 = 0.94), discharge (r2 = 0.96), turbidity (r2 = 0.71), transparency (r2 = -0.62), water temperature (r2 = 0.60), pH (r2 = -0.52) and DO (r2 = -0.48); water temperature with pH (r2 = -0.54), DO (r2 = -0.79), free CO2 (r2 = 0.69), total alkalinity (r2 = -0.58), total PO4 (r2 = 0.54) and NO3 (r2 = 0.62), etc. The enhancement of turbidity, conductivity, free CO2, phosphates and nitrates, while, suppression of transparency, pH and DO at the urban site indicated the urban influence. Journal of Institute of Science and TechnologyVolume 22, Issue 2, January 2018, page: 129-139

Staurosirella andino-patagonica sp. nov. (Bacillariophyta) from lake sediments in Patagonia, Argentina

Phytotaxa ◽  
2019 ◽  
Vol 402 (3) ◽  
pp. 131 ◽  
Author(s):  
JOSÉ MARÍA GUERRERO ◽  
MARÍA LUJÁN GARCÍA ◽  
EDUARDO A. MORALES
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Lake Sediments ◽  
Surface Sediments ◽  
Geographic Area ◽  
New Taxon ◽  
Diatom Flora ◽  
The Andes ◽  
Distinct Morphology ◽  
Scanning Electron

Staurosirella andino-patagonica, a new araphid diatom found in Holocene and recent surface sediments from lakes located in the Andes and adjacent steppe of Patagonia (Argentina), is described on the basis of light and scanning electron microscopy observations and comparison with related taxa. Although the elliptic valve outline of the new taxon resembles the smaller specimens of several Staurosirella species, ultrastructural features such as the presence of two spines on each virga and their distinct morphology -serrated with thickenings at the base- make Staurosirella andino-patagonica unique within the genus. Our study contributes to the knowledge of the Patagonian araphid diatom flora, a rather unexplored geographic area, and so we assume that, as additional areas are studied in detail, they will likely continue to yield new taxa.

Biogeochemistry of macrophytes, sediments and porewaters in thermokarst lakes of western Siberia in the discontinuous and continuous permafrost zone

2020 ◽  
Author(s):  
Rinat Manasypov ◽  
Oleg Pokrovsky ◽  
Liudmila Shirokova
Keyword(s):  
Trace Elements ◽  
Lake Sediments ◽  
Aquatic Plants ◽  
Lake Water ◽  
Western Siberia ◽  
The Arctic ◽  
Formation Mechanisms ◽  
Thermokarst Lakes ◽  
Continuous Permafrost ◽  
Thaw Lakes

<p>Despite high importance of macrophytes in shallow thaw lakes for control of major and trace nutrients in lake water, the chemical composition of different aquatic plants and trace element (TE) partitioning between macrophytes and lake water and sediments in the permafrost regions remain totally unknown. Here we sampled dominant macrophytes of thermokarst (thaw) lakes of discontinuous and continuous permafrost zones in Western Siberia Lowland (WSL) and we measured major and trace elements in plant biomass, lake water, lake sediments and sediment porewater. All 6 studies plants (Hippuris vulgaris L., Glyceria maxima (Hartm.) Holmb., Comarum palustre L., Ranunculus spitzbergensis Hadac, Carex aquatilis Wahlenb s. str., Menyanthes trifoliata L.), sizably accumulate macronutrients (Na, Mg, Ca), micronutrients (B, Mo, Nu, Cu, Zn, Co) and toxicants (As, Cd) relative to lake sediments. The accumulation of other trace elements including rare earth elements (REE) in macrophytes relative to pore waters and sediments was strongly species-specific. Under climate warmings scenario and the propagation of southern species northward, the accumulation of trace metals in aquatic plants of thermokarst lakes will produce preferential uptake of Cd, Pb, Ba from thermokarst lake water and sediments by the biomass of aquatic macrophytes. This may eventually diminish the transport of metal micronutrients from lakes to rivers and further to the Arctic Ocean.</p><p>Support from the RSF (RNF) grant 19-77-00073 “Experimental modeling of the formation mechanisms for elemental composition of water in thermokarst lakes of Western Siberia: vegetation effect”.</p>

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