ABSTRACT
The Devonian-Carboniferous transition marks a fundamental shift in the surface environment primarily related to changes in ocean-atmosphere oxidation states1,2, resulting from the continued proliferation of vascular land plants that stimulated the hydrological cycle and continental weathering3,4, glacioeustasy5,6, eutrophication and anoxic expansion in epicontinental seas3,4, and mass extinction events2,7,8. Here we present a comprehensive spatial and temporal compilation of geochemical data from 90 cores across the entire Bakken Shale (Williston Basin, North America). Our dataset allows for the detailed documentation of stepwise transgressions of toxic euxinic waters into the shallow oceans that drove a series of Late Devonian extinction events. Other Phanerozoic extinctions have also been related to the expansion of shallow-water euxinia, indicating that hydrogen sulfide toxicity was a key driver of Phanerozoic biodiversity.
Subject(s)
Extinction, Biological , Hydrogen Sulfide , Oceans and Seas , Oxygen , Spatio-Temporal Analysis , Biodiversity , Hydrogen Sulfide/analysis , Hydrogen Sulfide/poisoning , Atmosphere/chemistry , Water Cycle , Eutrophication , Datasets as Topic , Oxygen/analysis , Oxygen/metabolism , Oxidation-Reduction , Plants/metabolism , North America , History, Ancient , Geologic Sediments/chemistry , AnimalsABSTRACT
We used stable isotope ratios to determine the metabolic routing fraction of carbon and nitrogen in feathers in addition to faecal analysis to estimate diet overlap of six sympatric species of manakins in the eastern lowland forest of Ecuador. Collectively, all species varied from-23.7 to-32.7 for δ(13)C, and from 6.0 to 9.9 for δ(15)N, with Machaeropterus regulus showing isotopic differences from the other species. We developed a mixing model that explicitly addresses the routing of carbon and nitrogen to feathers. Interestingly, these results suggest a higher proportion of nitrogen and carbon derived from insects than anticipated based on feeding observations and faecal analysis. A concentration-dependent mixing isotopic model was also used to look at dietary proportions. While larvae and arachnids had higher δ(15)N values, these two groups may also be preferred prey of manakins and may be more assimilated into tissues, leading to a potential overestimation of the contribution to diet. This study supports the finding that manakin species, previously thought be primarily frugivorous, contain a significant amount of arthropods in their diet.
Subject(s)
Diet , Food Chain , Magnoliopsida/chemistry , Passeriformes/physiology , Animals , Carbon Isotopes/metabolism , Ecuador , Feathers/chemistry , Feces/chemistry , Female , Fruit/chemistry , Male , Mass Spectrometry , Nitrogen Isotopes/metabolismABSTRACT
A novel metal-organic replica of α-PbO(2) exhibits high capacity for capture of nerve agent surrogate.
Subject(s)
Chemical Terrorism/prevention & control , Chemical Warfare Agents/analysis , Lead/chemistry , Organometallic Compounds/chemistry , Organothiophosphorus Compounds/analysis , Oxides/chemistry , Crystallography , Organometallic Compounds/chemical synthesis , Oxides/chemical synthesis , Porosity , Solvents/chemistryABSTRACT
A method for the removal of siderite from geological samples to determine organic carbon isotope compositions using elemental analysis isotope ratio mass spectrometry is presented which includes calculations for % organic carbon in samples that contain diagenetic carbonate. The proposed method employs in situ acidification of geological samples with 6 N HCl and silver capsule sample holders and was tested on modern peach leaf samples (NIST 1547) and ancient lacustrine samples from Valles Caldera, New Mexico. The in situ acidification technique eliminates potential errors associated with the removal of soluble organic material using standard acid decanting techniques and allows for removal of the less soluble siderite, which is not efficiently removed using vapor acidification techniques.
