An organic record of terrestrial ecosystem collapse and recovery at the Triassic–Jurassic boundary in East Greenland

Terrestrial ecosystem collapse at the end of the Triassic Period coincided with a major mass extinction in the marine realm and has been linked to increasing atmospheric carbon dioxide, global warming, and fire activity. Extractable hydrocarbons in samples from the fluvial Triassic–Jurassic boundary section at Astartekløft, East Greenland were analyzed to investigate the molecular and isotopic organic record of biotic and environmental change during this event. Carbon isotopic compositions of individual plant wax lipids show a >4‰ negative excursion coinciding with peak extinction and a further decrease of 2‰ coinciding with peak pCO2 as estimated from the stomatal indices of fossil Gingkoales. An increase of ∼30‰ in the hydrogen isotopic compositions of the same plant wax lipids coincides with ecosystem collapse, suggesting that the biotic crisis was accompanied by strong hydrologic change. Concentrations of polycyclic aromatic hydrocarbons related to combustion also increase together with abrupt plant diversity loss and peak with fossil charcoal abundance and maximum plant turnover, supporting the role of fire in terrestrial extinctions. Anomalously high concentrations of a monoaromatic diterpenoid related to gymnosperm resin derivatives (and similar to dehydroabietane) occur uniquely in samples from the boundary bed, indicating that environmental stress factors leading to peak plant extinction stimulated increased resin production, and that plant resin derivatives may be effective biomarkers of terrestrial ecosystem stress

Bitumen II from the Paleoproterozoic Here’s Your Chance Pb/Zn/Ag deposit: Implications for the analysis of depositional environment and thermal maturity of hydrothermally-altered sediments

The formation of sedimentary exhalative (SEDEX) Pb/Zn deposits is linked to ocean euxinia, but recent evidence suggests that ferruginous conditions may have dominated the deep ocean during the Middle Proterozoic, a maximum period for SEDEX distribution. Biomarkers of sulfate-reducing and sulfide-oxidising bacteria are valuable indicators of euxinic conditions in such settings. Organic matter (OM) from SEDEX deposits is often affected by alteration and/or migration, but OM entrapped within the kerogen/mineral matrix (Bitumen II) may be less affected than the freely-extractable OM (Bitumen I). We analysed Bitumen II from the Paleoproterozoic Here’s Your Chance (HYC) Pb/Zn/Ag deposit to find evidence of euxinic conditions in the depositional environment. n-Alkane distributions in Bitumen II are markedly distinct from previously reported Bitumen I. Bitumen II contains long-chain n-alkanes (up to C36 or C38) and a strong even-over-odd distribution in a number of samples, which are 4& to 7& depleted in 13C compared to n-alkanes in Bitumen I and verified as indigenous by comparison with d13C of isolated kerogen.These features are interpreted as evidence of sulfate-reducing and sulfide-oxidising bacteria, confirming that HYC was deposited under euxinic conditions. Bitumen II has the potential to reveal information from OM that is degraded and/or overprinted in Bitumen I. Commonly-used methylphenanthrene maturity ratios give conflicting information as to the relative maturity of Bitumens I and II. Bitumen I contains a far higher proportion of methylated phenanthrenes than Bitumen II. As Bitumen II is sequestered within the kerogen/mineral matrix it may have restricted access to the ‘methyl pool’ of organic compounds that can donate methyl groups to aromatic hydrocarbons. Parameters that include both phenanthrene and methylphenanthrenes do not appear suitable to compare the maturity of Bitumens I and II; hence there is no clear evidence that Bitumen II is of lower thermal maturity than Bitumen I

New aspects of sulfur biogeochemistry during ore deposition from δ34S of elemental sulfur and organic sulfur from the Here's Your Chance Pb/Zn/Ag deposit

Sulfur isotope studies of base metal sulfide deposits have mostly focussed on sulfide minerals, but elemental sulfur and organic sulfur are also potentially significant components of the sulfur cycle during ore deposition. The δ34S of elemental sulfur and organic sulfur isolated from the Paleoproterozoic Here's Your Chance (HYC) Pb/Zn/Ag deposit (McArthur Basin, northern Australia) were measured to be between + 5 and + 8‰, approximately 6 to 7‰ heavier than the median values of first-generation HYC sulfides. Elemental sulfur and organic sulfur are thought to have been formed contemporaneously with the first generation of metal sulfides. The δ34S of organic sulfur showed an increasing trend along the path of the mineralising fluid, as sulfate was progressively 34S-enriched due to Rayleigh distillation. The δ34S data support a model in which bacterial sulfate reduction produced dissolved sulfide with δ34S of 0 to + 5‰. The subsequent oxidation of sulfide produced reactive sulfur species such as polysulfide ions, which were then incorporated into organic matter

White sharks exploit the sun during predatory approaches

There is no conclusive evidence of any nonhuman animal using the sun as part of its predation strategy. Here, we show that the world\u27s largest predatory fish-the white shark (Carcharodon carcharias)-exploits the sun when approaching baits by positioning the sun directly behind them. On sunny days, sharks reversed their direction of approach along an east-west axis from morning to afternoon but had uniformly distributed approach directions during overcast conditions. These results show that white sharks have sufficient behavioral flexibility to exploit fluctuating environmental features when predating. This sun-tracking predation strategy has a number of potential functional roles, including improvement of prey detection, avoidance of retinal overstimulation, and predator concealment

Observational study of the association of first insulin type in uncontrolled type 2 diabetes with macrovascular and microvascular disease

<p>Aims: To compare the risk of vascular disease, HbA1c and weight change, between first prescribed insulins in people with type 2 diabetes.</p> <p>Methods: People included in THIN United Kingdom primary care record database who began insulin (2000–2007) after poor control on oral glucose-lowering agents (OGLD) were grouped by the number of OGLDs in their treatment regimen immediately before starting insulin (n = 3,485). Within OGLD group, Cox regression compared macrovascular (all-cause mortality, myocardial infarction, acute coronary syndrome and stroke) and microvascular disease (peripheral neuropathy, nephropathy, and retinopathy) between insulin type (basal, pre-mix or Neutral Protamine Hagedorn, NPH) while ANCOVAs compared haemoglobin A1c (HbA1c) and weight change.</p> <p>Results: Mean follow-up was 3.6 years. Rates of incident macrovascular events were similar when basal insulin was compared to pre-mix or NPH, adjusted hazard ratio versus basal: pre-mix 1.08 (95% CI 0.73, 1.59); NPH 1.00 (0.63, 1.58) after two OGLDs, and pre-mix 0.97 (0.46, 2.02); NPH 0.77 (0.32, 1.86) after three OGLDs. An increased risk of microvascular disease in NPH versus basal after 3 OGLDs, adjusted hazard ratio1.87 (1.04, 3.36), was not seen after two agents or in comparisons of basal and pre-mix. At one year, after two OGLDs, weight increase was less with basal compared with pre-mix. After three OGLDs, mean HbA1c had reduced less in basal versus pre-mix or NPH at 6–8 and at 9–11 months, and versus pre-mix at 12–14 months.</p> <p>Conclusion: We found no difference in the risk of macrovascular events between first insulins in the medium term when started during poor glycaemia control. The increased risk of microvascular events with NPH warrants further study. In certain groups, first use of basal insulin was associated with less gain in weight and decrease in HbA1c compared to other insulins.</p&gt

Physical and digital architecture for collection and analysis of imparted accelerations on Zip Line attractions

The accelerations experienced by riders of Zip Line attractions is an underexplored area of public safety assurance. These amusement devices require complex processes to collect and analyze acceleration data. Highly versatile and effective rider-worn and ride-carried devices are necessary to collect acceleration and velocity data without affecting the integrity of the ride. This paper introduces the use of a sensor device for collecting Zip Line acceleration data in the form of a Trailing Trolley. This architecture extends the work of Sicat et. al.’s which proposed the use of a Sensor Vest and Headwear to collect linear and rotational accelerations of a Zip Line rider. We investigate the logistics of combining the two sensor platforms and formulate a procedure to post-process and analyze the data. Techniques to extract, filter, and process the accelerations recorded is discussed and the potential for the synthesis of positioning linear and rotational data is described. Additional testing of data collection and analysis is necessary to prove the viability of these techniques and apparatuses as potential parts of a standardized test method for measuring rider experienced g-forces on Zip Lines

Carbon and sulfur isotopic composition of alkyl- and benzo-thiophenes provides insights into their origins and formation pathways

Thiophenic compounds can provide significant geochemical information and may be used as paleoenvironmental indicators as long as their biological origins and formation pathways are understood. To this end, we investigated the structures, distributions, δ13C and δ34S values, of specific thiophenic compounds extracted from immature sedimentary rocks from the Upper Cretaceous (Ghareb Formation, Shefela Basin, Israel). Isoprenoidal alkylthiophenes (ATs) showed a general trend of depletion in their 13C and 34S values relative to the normal (linear) ATs extracted from the studied samples. In addition, a consistent enrichment of up to 2‰ in 13C and 8‰ in 34S of methylated ATs (m/z = 111), relative to non-methylated ones (m/z = 97), was recorded. This suggests that AT precursors derived from different organisms and diagenetic pathways, which later affected their sulfurization mechanisms. The large variation, of ∼15‰, in the δ34S values of individual ATs, along with the general trend of 13C depletion with increasing Tmax, suggests that ATs formed by a set of diagenetic processes of mild thermochemical alteration. The δ13C values of benzothiophenes (BTs) were enriched in 13C relative to the rest of the organic sulfur compounds; by ∼3‰ on average. This in turn suggests that BTs were generated mainly by sulfurization and subsequent ring closure, or aromatization of 13C-enriched aromatic/alkyl cyclohexane compounds with unsaturation and/or functional groups in their alkyl chain. Such 13C-enriched precursors can be generated from carotenoids and terrestrial compounds (e.g., by lignin degradation). The large variation in δ34S values of individual BTs, of ∼15‰, suggests that the BTs in our samples were formed during diagenesis and did not experience advanced thermal alteration processes. Therefore, their occurrence in immature sedimentary rocks might be used as a proxy for early thermochemical alteration that cannot be detected using conventional geochemical indicators, such as Tmax. The combination of structural, 13C and 34S investigations of individual organic sulfur compounds enhanced an understanding of their sulfurization pathways and origins, which in turn may expand their utilization as paleoenvironmental indicators

Levels of autotrophy and heterotrophy in mesophotic corals near the end photic zone

Mesophotic corals live at ~30-150 m depth and can sustain metabolic processes under light-limited conditions by enhancing autotrophy through specialized photoadaptations or increasing heterotrophic nutrient acquisition. These acclimatory processes are often species-specific, however mesophotic ecosystems are largely unexplored and acclimation limits for most species are unknown. This study examined mesophotic coral ecosystems using a remotely operated vehicle (Ashmore Reef, Western Australia at 40 – 75m depth) to investigate the trophic ecology of five species of scleractinian coral (from genera Leptoseris, Pachyseris, and Craterastrea) using stable isotope analyses (δ13C and δ15N) of host and symbiont tissues and protein concentration. Trophic strategies were analyzed between species and between overall corals sampled above and below the end-photic point, where light is only 1% of surface irradiance. Results showed species-specific differences in resource use. Leptoseris hawaiiensis, L. scabra, and P. speciosa had similar Δ13C values (δ13C host - δ13C symbiont) approaching zero ( \u3c 0.5 ‰) which indicated greater dependence on symbiont autotrophy. In contrast, Leptoseris glabra and Craterastrea levis had higher Δ13C values (1.4 to 3.5 ‰) which indicated a greater reliance on external carbon sources. The latter two species also demonstrated tight nitrogen recycling within the holobiont, exhibiting low Δ15N values (host δ15N - symbiont δ15N = \u3c 0.5 ‰), compared to more autotrophic species (Δ15N = \u3e 1.2 ‰). Some species demonstrated the ability to maintain metabolic processes despite substantially reduced light availability (0.5 – 2% of surface irradiance). This research challenges our knowledge of acclimation limits for many scleractinian corals and contributes novel information for Ashmore Reef, the Western Australia region and mesophotic ecosystems in general, and critically examines common methods used to interpretate trophic ecology with bulk stable isotopes δ13C and δ15N

Fire distinguishers: Refined interpretations of polycyclic aromatic hydrocarbons for paleo-applications

Polycyclic aromatic hydrocarbons (PAHs), produced via incomplete combustion of organics, convey signatures of vegetation burned in the geologic past. New and published burn experiments reveal how the quantity, distributions, and isotopic abundances of fire-derived PAHs were influenced by fuel types, burn conditions, and also phase. PAH concentrations were higher in burn residues from moderate burn temperatures (400–500 °C), and significantly lower in residues from cooler (600 °C) conditions, especially when oxygen was limited. PAH forms tended to be smaller in smoke samples and larger in residues, consistent with molecular physical and chemical properties. Plant functional types were distinguished by relative amounts of retene and dimethyl phenanthrene isomers. Isotopically distinct photosynthetic pathways of the burned material were reflected in the δ13C values of PAHs, which faithfully captured biomass signatures as well as the ∼12‰ offset between C3 and C4 plant types. PAH size, alkylation, and isotope characteristics can differentiate combusted plant types and distinguish between air-borne and sedimentary transport mechanisms. New proxy approaches using PAH amounts, distributions, and isotope signatures can aid and refine interpretations of paleofire ecology in the geologic record

Characterizations and comparison of low sulfur fuel oils compliant with 2020 global sulfur cap regulation for international shipping

© The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Nelson, R. K., Scarlett, A. G., Gagnon, M. M., Holman, A. I., Reddy, C. M., Sutton, P. A., & Grice, K. Characterizations and comparison of low sulfur fuel oils compliant with 2020 global sulfur cap regulation for international shipping. Marine Pollution Bulletin, 180, (2022): 113791, https://doi.org/10.1016/j.marpolbul.2022.113791.The International Marine Organization 2020 Global Sulfur Cap requires ships to burn fuels with <0.50% S and some countries require <0.10% S in certain Sulfur Emission Control Areas but little is known about these new types of fuels. Using both traditional GC–MS and more advanced chromatographic and mass spectrometry techniques, plus stable isotopic, δ13C and δ2H, analyses of pristane, phytane and n-alkanes, the organic components of a suite of three 0.50% S and three 0.10% S compliant fuels were characterized. Two oils were found to be near identical but all of the remaining oils could be forensically distinguished by comparison of their molecular biomarkers and by the profiles of the heterocyclic parent and alkylated homologues. Oils could also be differentiated by their δ13C and δ2H of n-alkanes and isoprenoids. This study provides important forensic data that may prove invaluable in the event of future oil spills.This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. CMR and RKN were supported by the National Science Foundation (OCE-1634478 and OCE-1756242). GC × GC analysis support provided by WHOI's Investment in Science Fund