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.

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 Statistical Characteristics of Unsteady Storms in Radar Observations for the Beijing–Tianjin Region

2015 ◽  
Vol 54 (1) ◽  
pp. 106-116 ◽  
Author(s):  
Yu Wang ◽  
Hong-Qing Wang ◽  
Lei Han ◽  
Yin-Jing Lin ◽  
Yan Zhang
Keyword(s):  
Warm Season ◽  
Environmental Parameters ◽  
Statistical Characteristics ◽  
Movement Speed ◽  
Movement Direction ◽  
Upper Troposphere ◽  
Maximum Value ◽  
Dynamic Factors ◽  
The Mean ◽  
Wind Profiles

AbstractThis study was designed to provide basic information for the improvement of storm nowcasting. According to the mean direction deviation of storm movement, storms were classified into three types: 1) steady storms (S storms, extrapolated efficiently), 2) unsteady storms (U storms, extrapolated poorly), and 3) transitional storms (T storms). The U storms do not fit the linear extrapolation processes because of their unsteady movements. A 6-yr warm-season radar observation dataset was used to highlight and analyze the differences between U storms and S storms. The analysis included geometric features, dynamic factors, and environmental parameters. The results showed that storms with the following characteristics changed movement direction most easily in the Beijing–Tianjin region: 1) smaller storm area, 2) lower thickness (echo-top height minus base height), 3) lower movement speed, 4) weaker updrafts and the maximum value located in the mid- and upper troposphere, 5) storm-relative vertical wind profiles dominated by directional shear instead of speed shear, 6) lower relative humidity in the mid- and upper troposphere, and 7) higher surface evaporation and ground roughness.

Interstadial Conifer Wood from Northern Maine

1988 ◽  
Vol 30 (1) ◽  
pp. 98-101
Author(s):  
R. Scott Anderson ◽  
Ronald B. Davis ◽  
Robert Stuckenrath ◽  
Harold W. Borns
Keyword(s):  
Organic Matter ◽  
New England ◽  
Lake Sediments ◽  
Lake Sediment ◽  
Radiocarbon Dating ◽  
Late Glacial ◽  
Local Source ◽  
Northern New England ◽  
Upper South ◽  
Conifer Wood

Conifer wood, probably spruce (Picea sp.), of middle Wisconsinan age (29,200 ± 500 yr B.P.) was recovered from late-glacial lake sediments from Upper South Branch Pond, Maine. If the wood was derived from a local source, deglaciation of part of northern New England is suggested for this time. The occurrence also has implications for understanding the problem associated with radiocarbon dating of bulk lake sediment containing small amounts of organic matter.

scholarly journals The Cell Membrane of Sulfolobus spp.—Homeoviscous Adaption and Biotechnological Applications

2020 ◽  
Vol 21 (11) ◽  
pp. 3935 ◽  
Author(s):  
Kerstin Rastädter ◽  
David J. Wurm ◽  
Oliver Spadiut ◽  
Julian Quehenberger
Keyword(s):  
Cell Membrane ◽  
Environmental Changes ◽  
Specific Growth ◽  
Membrane Lipids ◽  
Environmental Parameters ◽  
Coping Mechanism ◽  
Biotechnological Applications ◽  
Head Groups ◽  
Tetraether Lipids ◽  
Archaeal Lipids

The microbial cell membrane is affected by physicochemical parameters, such as temperature and pH, but also by the specific growth rate of the host organism. Homeoviscous adaption describes the process of maintaining membrane fluidity and permeability throughout these environmental changes. Archaea, and thereby, Sulfolobus spp. exhibit a unique lipid composition of ether lipids, which are altered in regard to the ratio of diether to tetraether lipids, number of cyclopentane rings and type of head groups, as a coping mechanism against environmental changes. The main biotechnological application of the membrane lipids of Sulfolobus spp. are so called archaeosomes. Archaeosomes are liposomes which are fully or partly generated from archaeal lipids and harbor the potential to be used as drug delivery systems for vaccines, proteins, peptides and nucleic acids. This review summarizes the influence of environmental parameters on the cell membrane of Sulfolobus spp. and the biotechnological applications of their membrane lipids.

Carbon Isotope Composition of Lake Sediments in Relation to Lake Productivity and Radiocarbon Dating

1992 ◽  
Vol 37 (3) ◽  
pp. 333-345 ◽  
Author(s):  
Ramon Aravena ◽  
Barry G. Warner ◽  
Glen M. MacDonald ◽  
Karen I. Hanf
Keyword(s):  
Lake Sediments ◽  
Lake Sediment ◽  
Lake Water ◽  
Dissolved Inorganic Carbon ◽  
Isotope Composition ◽  
Hard Water ◽  
Lake Basin ◽  
Lake Productivity ◽  
Radiocarbon Dates ◽  
Organic Sediment

AbstractCarbon-13 profiles and radiocarbon dates were obtained from two Canadian kettle basins having similar geological and hydrological characteristics to develop criteria for evaluating the validity of radiocarbon dates on lake sediment from basins in calcareous terrain. Radiocarbon dates from a site in Alberta show a variable hard-water effect related to local hydrological changes during postglacial history of the lake basin, whereas radiocarbon dates from the other site in Ontario show no noticeable influence of old carbon during its history. These differences are mainly related to lake water residence time, which has influenced carbon isotopic exchange between atmospheric CO2 and dissolved inorganic carbon in lake water. δ13C values for bulk organic sediment and terrestrial and aquatic macrofossils reveal that the main component of lake sediment at both sites is autocthonous in origin. Furthermore, each site supported different submerged aquatic plant communities that used different sources of carbon for photosynthesis, thereby imprinting the organic sediments with a characteristic 13C composition. Both sites reflect a clear relationship between 13C values and paleoproductivity. This study shows the individualistic response of the developing lake system to the hydrology, lake biota, and local geology, and demonstrates the problem of using 13C in lake sediments as a single criterion to recognize the validity of radiocarbon dates of lake sediment without supporting paleoecological information.

scholarly journals Assessing the Efficacy of A Marine Reserve to Protect Sharks With Differential Habitat Use

2020 ◽  
Author(s):  
Cesar Peñaherrera-Palma ◽  
Alistair Hobday ◽  
Alex Hearn ◽  
Eduardo Espinoza ◽  
George Shillinger ◽  
...  
Keyword(s):  
Marine Reserve ◽  
Warm Season ◽  
Environmental Parameters ◽  
Marine Species ◽  
Cold Season ◽  
Utilization Distribution ◽  
The North ◽  
South Central ◽  
Central Regions ◽  
Hammerhead Sharks

Abstract Spatial management through the implementation of marine protected areas is one strategy to limit the extraction of sensitive marine species. Understanding the area used by marine life is thus a key step towards the evaluation of the management framework and efficacy of a protected area. To provide information of the protective coverage of the Galapagos Marine Reserve (GMR), we assessed the habitat utilization distribution (UD) of hammerhead and blacktip sharks in the GMR. Fifteen hammerhead sharks and 27 blacktip sharks were tagged with SPOT and SPLASH satellite tags in the north and south-central regions of the GMR between 2007 and 2012. Our results show nearly 90% of hammerhead shark’s UD was enclosed by the reserve boundary during the cold season (June-October), yet this decreased to only ~30% with the advent of the warm season (December-April). Conversely, blacktip sharks’ UD was 100% enclosed by the reserve boundaries in all seasons. Season and depth were the most important environmental parameters defining the UD of hammerhead sharks; whilst year and eddy kinetic energy were the most important parameters for blacktip sharks. These findings suggest the size of the GMR may be effective for blacktip sharks but seasonally effective for hammerhead sharks.

scholarly journals Radiocarbon Dating of Lake Sediment from Two Karst Lakes in Yugoslavia

Radiocarbon ◽  
1986 ◽  
Vol 28 (2A) ◽  
pp. 495-502 ◽  
Author(s):  
Dušan Srdoč ◽  
Bogomil Obelić ◽  
Nada Horvatinčić ◽  
Ines Krajcar-Bronić ◽  
Elena Marčenko ◽  
...  
Keyword(s):  
Lake Sediments ◽  
Lake Sediment ◽  
Sedimentation Rate ◽  
National Park ◽  
Radiocarbon Dating ◽  
Sediment Cores ◽  
Karst Area ◽  
Seismic Profiles ◽  
Karst Lakes ◽  
Isotopic Studies

Samples of sediment cores from two lakes in the karst area of northwest Yugoslavia were analyzed. Both Lakes Kozjak and Prošće are in the Plitvice National Park, Central Croatia. 14C dating, sedimentologic, seismic, and isotopic studies, and distribution of diatoms are presented.14C dating of lake marl revealed a uniforn sedimentation rate in Lake Prošće as opposed to Lake Kozjak. Both lake sediments belong to the Holocene period. 14C dating of lake sediment is in agreement with seismic profiles, sedimentologic analysis, and diatom frequency measurements both in an undisturbed as well as in a disturbed lake sediment.

Comparative assessment of the microclimate in the «Cape Martyan» Nature Reserve according to two weather stations

2019 ◽  
pp. 34-43
Author(s):  
S. P. Korsakova ◽  
P. B. Korsakov
Keyword(s):  
Relative Humidity ◽  
Nature Reserve ◽  
Warm Season ◽  
Comparative Assessment ◽  
Meteorological Station ◽  
Air Temperatures ◽  
Spatio Temporal ◽  
Meteorological Observations ◽  
Conducting Research ◽  
Night Period

A comparative assessment of the microclimate in the «Cape Martyan» Nature Reserve according to meteorological observations in meteorological station "Lavrovoe" and the climate agrometeorological station "Nikitsky sad" is given. As a result of the conducted researches homogeneity and spatio-temporal connectedness of climatic parameters within the investigated territory is established. Statistically significant differences in average and maximum values of air temperature, precipitation and relative humidity between the meteorological station "Lavrovoe" and the climate agrometeorological station "Nikitsky sad" were not revealed. This indicates to the representativeness of the data agrometeorological station for the territory of the «Cape Martyan» Nature Reserve. Statistically significant differences established for minimum air temperatures and relative humidity during the cold period should be taken into account when conducting research in the Eastern part of the Nature Reserve. It was found that the wind regime in the area of the observations by meteorological station "Lavrovoe" in the night period is characterized by air drainage phenomena and the predominance of breeze circulation in the warm season, which largely determine the microclimatic differences between observed meteorological values by station "Lavrovoe" and by station "Nikitsky sad", especially when the radiation weather type.

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