Introduction to “isotopic signatures and sedimentary records”

AbstractEarth’s crust contains a substantial proportion of global biomass, hosting microbial life up to several kilometers depth. Yet, knowledge of the evolution and extent of life in this environment remains elusive and patchy. Here we present isotopic, molecular and morphological signatures for deep ancient life in vein mineral specimens from mines distributed across the Precambrian Fennoscandian shield. Stable carbon isotopic signatures of calcite indicate microbial methanogenesis. In addition, sulfur isotope variability in pyrite, supported by stable carbon isotopic signatures of methyl-branched fatty acids, suggest subsequent bacterial sulfate reduction. Carbonate geochronology constrains the timing of these processes to the Cenozoic. We suggest that signatures of an ancient deep biosphere and long-term microbial activity are present throughout this shield. We suggest that microbes may have been active in the continental igneous crust over geological timescales, and that subsurface investigations may be valuable in the search for extra-terrestrial life.

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Ontogenetic shift in the trophic role of the invasive killer shrimp Dikerogammarus villosus: a stable isotope study

Biological Invasions ◽

10.1007/s10530-021-02472-0 ◽

2021 ◽

Author(s):

Francesco Mancini ◽

Raffaele De Giorgi ◽

Alessandro Ludovisi ◽

Salvatrice Vizzini ◽

Giorgio Mancinelli

Keyword(s):

Dietary Habits ◽

Trophic Position ◽

Ecological Impact ◽

Central Italy ◽

Local Conditions ◽

Dikerogammarus Villosus ◽

Isotopic Signatures ◽

Depth Analysis ◽

Stable Isotope Study ◽

The Impact

AbstractThe introduction of the amphipod Dikerogammarus villosus in European fresh waters is to date recognized as a threat to the integrity of invaded communities. Predation by D. villosus on native benthic invertebrates is assumed as the key determinant of its ecological impact, yet available information describe the species as a primary consumer as well as a carnivore depending on local conditions. Here, we assessed the trophic position (TP) of D. villosus in Lake Trasimeno, a recently invaded lentic system in central Italy, using the CN isotopic signatures of individuals captured in winter spanning two orders of magnitude in body size. TP estimations were compared with those characterizing the native amphipod Echinogammarus veneris and other representative invertebrate predators. On average, D. villosus showed a trophic position higher than E. veneris, and comparable with that of odonate nymphs. An in-depth analysis revealed that large-sized individuals had a trophic position of 3.07, higher than odonates and close to that of the hirudinean predator Erpobdella octoculata, while small-sized specimens had a trophic position of 2.57, similar to that of E. veneris (2.41). These findings indicate that size-related ontogenetic shifts in dietary habits may per se vary the nature of the interaction between Dikerogammarus villosus and native invertebrates from competition to predation. Information collated from published isotopic studies corroborated the generality of our results. We conclude that intra-specific trophic flexibility may potentially amplify and make more multifaceted the impact of the species on other invertebrate species in invaded food webs.

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Noble gas isotopic signatures of sulfides in carbonatites of the Vuoriyarvi alkaline-ultrabasic complex (Kola Region, NW Russia)

Arabian Journal of Geosciences ◽

10.1007/s12517-021-07884-9 ◽

2021 ◽

Vol 14 (17) ◽

Author(s):

Evgeniy Kozlov ◽

Vladimir Skiba ◽

Ekaterina Fomina ◽

Mikhail Sidorov

Keyword(s):

Noble Gas ◽

Isotopic Signatures ◽

Kola Region

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Temperature affects carbon and nitrogen stable isotopic signatures of aquatic plants

Aquatic Sciences ◽

10.1007/s00027-021-00794-8 ◽

2021 ◽

Vol 83 (2) ◽

Author(s):

Peiyu Zhang ◽

Xianghong Kong ◽

Elisabeth S. Bakker ◽

Jun Xu ◽

Min Zhang

Keyword(s):

Aquatic Plants ◽

Isotopic Signatures ◽

Carbon And Nitrogen ◽

Stable Isotopic

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Radiogenic Pb Enrichment of Mississippi Valley-Type Metallic Ore Deposits, Southern Ozarks: Constraints Based on Geochemical Studies of Source Rocks and Their Diagenetic History

Geosciences ◽

10.3390/geosciences11040172 ◽

2021 ◽

Vol 11 (4) ◽

pp. 172

Author(s):

Jonathan Chick ◽

Sydney E. McKim ◽

Adriana Potra ◽

Walter L. Manger ◽

John R. Samuelsen

Keyword(s):

Linear Trend ◽

Ore Deposits ◽

Source Rocks ◽

Mississippi Valley ◽

Isotopic Signatures ◽

Boone Formation ◽

Tripolitic Chert ◽

Geochemical Studies ◽

Mississippi Valley Type ◽

Valley Type

Southern Ozark Mississippi Valley-type ores are enriched in radiogenic Pb, with isotopic signatures suggesting that metals were supplied by two end-member components. While the less radiogenic component appears to be derived from various shale and sandstone units, the source of the more radiogenic component has not yet been identified. Analyses of cherts from the Early Ordovician Cotter Dolomite and tripolitic chert from the Early Mississippian Boone Formation contain highly radiogenic Pb, with isotopic ratios comparable to those of ores. However, most samples have lower 208Pb/204Pb and 207Pb/204Pb for a given 206Pb/204Pb compared to ores. These relationships demonstrate that the enriched Pb isotopic values of the ore array cannot be related to the host and regional lithologies sampled, suggesting that the source of high ratios may lay further afield. The slope of the linear trend defined by the Pb isotope ratios of ores corresponds to an age of about 1.19 Ga. Therefore, an alternative for the linear array is the involvement of Precambrian basement in supplying ore Pb. Rare earth element patterns show that diagenetic processes involving the action of groundwater and hydrothermal fluids affected the sampled lithologies to various degrees, with Cotter Dolomite having experienced the highest degree of alteration.

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