Compound-­Specific Hydrogen Isotopes of Lipid Biomarkers in Lake El’gygytgyn, Ne Russia

Recent successful drilling operations at Lake El\u27gygytgyn, NE Russia have recovered sediment cores back to 3.6Ma, representing the longest time-continuous sediment record of past climate change in the terrestrial Arctic. Analysis of the hydrogen isotopic ratio (δD) of specific organic biomarkers allows reconstruction of past hydrological conditions, thereby providing a powerful tool for reconstructing past Arctic climate changes. Compound specific isotopic analysis of sedimentary lipids from this remote basin provides new insights into the climate evolution of the Arctic, capturing the mechanisms and dynamics of the last two glacial-interglacial transitions, potentially enhancing the accuracy of modeled future climate change projections and presenting an opportunity to estimate past polar amplification of climate change. The results of this research document the first continuous, high fidelity continental record of reconstructed δD in precipitation from terrestrial plant leaf waxes in the High Arctic spanning the last 120 ka. The hydrogen isotopic composition of lipid biomarkers were determined from previously obtained Lake El\u27gygytgyn sediment cores and compared with other multi-proxy evidence of past climate change within the lake basin. The modern isotope hydrology and controls on the δD lipid signal were first established within the El\u27gygytgyn Basin from modern precipitation, stream and lake waters, ice cover as well as modern vegetation, water column and lake bottom surface sediments in order to provide a modern context to properly constrain and interpret paleoclimatic proxy data. Reconstructed δD records of paleoprecipitation and temperature at Lake El\u27gygytgyn lead other northern hemisphere climate records (e.g. North Greenland Ice Core Project, NGRIP δ18O records) and are in phase with other continental and Antarctic climate records, suggesting early high northern latitude continental warming prior to established glacial-interglacial transitions. The data set generated here leads to multiple avenues of future work and provides critical insights into Arctic paleoclimate and paleohydrology, contributing to our understanding of high latitude environmental change over geological timescales. Collectively, the results of this dissertation research will provide a context for paleoclimate reconstructions and future organic geochemical and stable isotope analysis. Future application of compound-specific H isotope analyses to long drill cores (recovered in 2009; ~315m of sediment) will potentially provide a quantitative high-resolution record of paleoclimatic and paleoenvironmental changes spanning the last 3.6 Ma

Fluvial response to late Holocene glacier fluctuations in the Nostetuko River valley, southern Coast Mountains, British Columbia

Late Holocene glacier fluctuations and changes in bed elevation are recorded in the alluvial fill of the west fork Nostetuko River valley, southern Coast Mountains, British Columbia. Valley-wide aggradation coincides with periods of local and regional glacier advance on centennial timescales. Peat layers containing in situ tree roots and stumps formed during periods of floodplain stability that coincide with intervals when glaciers were restricted. Radiocarbon ages on roots, tree stems, and woody plant detritus in the peat layers record five major phases of Holocene glacier advance, the most recent at the culmination of the Little Ice Age. A high-resolution record of Little Ice Age glacier fluctuations was derived by cross-dating ring-width series of fossil trees in the peat layers with a previously established master ring-width chronology and by constraining floating ring-width chronologies with radiocarbon ages

Modern isotope hydrology and controls on dD of plant leaf waxes at Lake El’gygytgyn, NE Russia

Stable isotope data from lipid biomarkers and diatom silica recovered from lake sediment cores hold great promise for paleoclimate and paleohydrological reconstructions. However, these records rely on accurate calibration with modern precipitation and hydrologic processes and only limited data exist on the controls on the δD values for n-alkanoic acids from plant leaf waxes. Here we investigate the stable isotopic composition of modern precipitation, streams, lake water and ice cover, and use these data to constrain isotope systematics of the Lake El'gygytgyn Basin hydrology. Compound-specific hydrogen isotope ratios determined from n-alkanoic acids from modern vegetation are compared with modern precipitation and lake core top sediments. Multi-species net (apparent) fractionation values between source water (precipitation) and modern vegetation (e.g., ϵwax/precip mean value is −107 ± 12‰) agree with previous results and suggest a consistent offset between source waters and the δD values of alkanoic acids. We conclude that although there may be some bias towards a winter precipitation signal, overall δD values from leaf wax n-alkanoic acids record annual average precipitation within the El'gygytgyn Basin. A net fractionation calculated for 200-yr-integrated lake sediments yields ϵ30/precip = −96 ± 8‰ and can provide robust net "apparent" fractionation to be used in future paleohydrological reconstructions

ACTN3 (R577X) genotype is associated with Australian football league players

Jacob, Y, Hart, NH, Cochrane, JL, Spiteri, T, Laws, SM, Jones, A, Rogalski, B, Kenna, J, and Anderton, RS. ACTN3 (R577X) genotype is associated with Australian Football League players. J Strength Cond Res XX(X): 000–000, 2020—Genetic variants in the angiotensin-converting enzyme (ACE) and alpha actinin-3 (ACTN3) genes have been associated with elite sport athletic performance. This study aimed to investigate the frequency of each polymorphism in a cohort of elite Australian football (AF) players. To achieve this, 47 players from an Australian Football League (AFL) club and 59 healthy age matched controls with no history of elite sporting competition were recruited for this study. Each subject provided saliva samples through buccal swab for DNA extraction and genotyping, with group comparisons made using χ2 and odds ratio analysis. There was no significant difference in ACE I/D genotype between healthy control and elite AF players. The ACTN3 XX genotype was significantly underrepresented in AFL players (4.3%) compared with healthy controls (28.8%, p = 0.003). In addition, there was a greater representation of the R allele in elite AF players (70.2%) when compared with healthy controls (50%; χ2 = 8.834, p = 0.002). This is the first study to investigate genetic variants in elite AF players, with results suggesting that the ACTN3 gene may play a significant role explaining aspects of athletic performance in AF

Variations in microbial carbon sources and cycling in the deep continental subsurface

Deep continental subsurface fracture water systems, ranging from 1.1 to 3.3 km below land surface (kmbls), were investigated to characterize the indigenous microorganisms and elucidate microbial carbon sources and their cycling. Analysis of phospholipid fatty acid (PLFA) abundances and direct cell counts detected varying biomass that was not correlated with depth. Compound-specific carbon isotope analyses (δ13C and Δ14C) of the phospholipid fatty acids (PLFAs) and carbon substrates combined with genomic analyses did identify, however, distinct carbon sources and cycles between the two depth ranges studied. In the shallower boreholes at circa 1 kmbls, isotopic evidence indicated microbial incorporation of biogenic CH4 by the in situ microbial community. At the shallowest site, 1.05 kmbls in Driefontein mine, this process clearly dominated the isotopic signal. At slightly deeper depths, 1.34 kmbls in Beatrix mine, the isotopic data indicated the incorporation of both biogenic CH4 and dissolved inorganic carbon (DIC) derived from CH4 oxidation. In both of these cases, molecular genetic analysis indicated that methanogenic and methanotrophic organisms together comprised a small component (<5%) of the microbial community. Thus, it appears that a relatively minor component of the prokaryotic community is supporting a much larger overall bacterial community in these samples. In the samples collected from >3 kmbls in Tau Tona mine (TT107, TT109 Bh2), the CH4 had an isotopic signature suggesting a predominantly abiogenic origin with minor inputs from microbial methanogenesis. In these samples, the isotopic enrichments (δ13C and Δ14C) of the PLFAs relative to CH4 were consistent with little incorporation of CH4 into the biomass. The most 13C-enriched PLFAs were observed in TT107 where the dominant CO2-fixation pathway was the acetyl-CoA pathway by non-acetogenic bacteria. The differences in the δ13C of the PLFAs and the DIC and DOC for TT109 Bh2 were ∼−24‰ and 0‰, respectively. The dominant CO2-fixation pathways were 3-HP/4-HB cycle > acetyl-CoA pathway > reductive pentose phosphate cycle