δ13C Data Research Articles

Carbon translocation within land snails affects the carbon isotopic fractionation

Stable carbon isotope composition (δ13C) of land snail materials is widely used as a proxy for reconstructing past vegetation and environmental changes. Interpretation δ13C data is challenging due to the complexities of snail physiology. This study cultured Lissachatina fulica (Bowdich, 1822) snails to investigate δ13C of their soft tissues and excrement under various plant types and dietary carbonate content. Our results show that snails primarily assimilate organic matter (OM), with limited use of dietary carbonates. δ13C of organic matter in excrement correlates positively with that in the diet, but exhibits deviations due to variable carbon isotopic fractionation during assimilation. Tissue δ13C (δ13Ctissue) is positively related to the δ13C of OM (δ13COM) in the diet, varying by turnover rates, with faster turnover rate, such as the digestive gland, exhibiting more negative δ13Ctissue values. Moreover, carbon isotopic fractionation between tissues and diet (Δ13Ctissue-OM) differs based on plant type. Snails fed with C3 plants show positive Δ13Ctissue-OM values, whereas those fed with C4 plants exhibit negative values. These Δ13Ctissue-OM values are far from equilibrium (Δ13Ctissue-OM = 0) with conditions of rapid snail growth. Our findings indicate that the snails fed with C3 and C4 plants result in distinct carbon isotopic fractionation, leading to the deviation in δ13C between plants and land snail materials (e.g., excrement, tissues, shells and shell-bound organic matter). A comprehensive model of carbon metabolism and isotopic fractionation in snails is proposed including the assimilation process from diet to soft tissues and excretion. This study highlights the importance of physiological factors such as growth rates and turnover rates when interpreting δ13C of land snail materials for paleoenvironmental reconstructions.

Evolution of carbon isotope composition in atmospheric CO2 during the early Toarcian

The large negative carbon isotope excursions during the Toarcian Oceanic Anoxic Event (T-CIE) implicate the injections of 13C-depleted CO2 into the Earth's ocean-atmosphere system, with multiple climate-sensitive carbon reservoirs as possible carbon sources. The carbon isotopic composition of atmospheric CO2 (δ13Cco2) is an important parameter of the Earth's carbon cycle and is crucial for exploring the causes of carbon-isotope excursions and understanding the carbon cycle-climate feedbacks. Here we compile δ13C and δ18O data of brachiopod shells and belemnite rostra sampled from two well-known sections calibrated with high-resolution biostratigraphy in Peniche (Portugal) and Yorkshire (England). According to the equilibrium between δ13CDIC (carbon isotopic composition of oceanic dissolved inorganic carbon) and δ13Cco2, we reconstruct the evolution of δ13Cco2 from brachiopod and belemnite δ13C records from the late Pliensbachian to the early Toarcian. Our results indicate that the brachiopod-based δ13Cco2 trend shows a short negative carbon isotope excursion from −7 ‰ to −8 ‰ at the Pliensbachian–Toarcian boundary, followed by a gradual positive excursion from −8 ‰ to −5 ‰ in the Polymorphum Zone, which is interrupted by a ∼ 3 ‰ negative excursion during the T-OAE. After careful consideration of the vital fractionation and living habitats of the belemnites, the belemnite-based δ13Cco2 trend shows a similar trend of temporal variations to that from the coeval brachiopods with a clear negative CIE (∼2.2 ± 0.4 ‰) during T-OAE. The low atmospheric δ13Cco2 values relative to volcanic gas (−3.8 to −4.6 ‰) suggest that volcanogenic CO2 is unlikely to result in such negative carbon-isotopic excursion directly during the Early Toarcian. Using the carbon isotopic records of plant tissue from Portugal section, combined with our reconstructed δ13Cco2, we conclude that plant carbon isotopic discrimination (△δ13Cplant) varied from 15.7 ‰ to 24.3 ‰ during the early Toarcian, with a maximum occurring during the T-OAE, which should be a combined record of environmental factors.

Distinct responses of climate-growth and iWUE in Fagus sylvatica L. at two low elevation sites in southern Italy

In this study, using a dendrological and isotopic approaches, we investigated the responses to climate of two pure Fagus sylvatica L. stands (Campobraca and Falode) in the southernmost part of the distribution range in southern Italy. The δ13C data were used for calculating the intrinsic water use efficiency (iWUE) as a proxy of the balance between the water and carbon cycles. The results showed that the iWUE of both stands was sensitive to the amount of precipitation during the summer months (negative, significant effect) and to atmospheric CO2 concentration. Growth was sensitive to climate only in the Campo Braca site; the most influential variables were the VPD (vapour pressure deficit) and precipitation of the summer months that had a negative and a positive effect, respectively. The iWUE showed a negative correlation with growth in Campo Braca and a non-significant one in Falode. Water availability was the most influential variable on F. sylvatica growth and physiology. The iWUE increase was mainly driven by atmospheric CO2 concentration, and by decreased precipitation, as a response of the trees to drought. Our results highlight the importance of understanding the hydrological changes due to climate change for forecasting/modelling forest responses. CO2 increase does not compensate for the effect of adverse climate on F. sylvatica in the forests of southern Italy, while local conditions play an important role in determining tree growth.

Using DIC‐δ13C Pair to Constrain Anthropogenic Carbon Increase in the Southeastern Atlantic Ocean Over the Most Recent Decade (2010–2020)

AbstractThe southeastern Atlantic Ocean is a crucial yet understudied region for the ocean absorption of anthropogenic carbon (Canth). Data from the A12 (2020) and A13.5 (2010) cruises offer an opportunity to examine changes in dissolved inorganic carbon (DIC), its stable isotope (δ13C), and Canth over the past decade within a limited region (1∼3°E, 32∼42°S). For the decade of 2010–2020, Canth invasion was observed from the sea surface down to 1,200 m based on both DIC and δ13C data. The mean Canth increase rate (1.08 ± 0.26 mol m−2 yr−1) during this period accelerated from 0.87 ± 0.05 mol m−2 yr−1 during the previous period (1983/84–2010). The δ13C‐based Canth increase closely matches the DIC‐based estimation below 500 m but is 26% higher in the upper ocean. This discrepancy is likely due to δ13C's longer air‐sea exchange timescale, seasonal variability in the upper ocean, and the chosen ratio of anthropogenically induced changes in δ13C and DIC. Finally, column inventory changes based on the two methods also exhibit very similar mean Canth uptake rates. The paired DIC concentration and stable isotope dataset may enhance our ability to constrain Canth accumulation and its controlling mechanisms in the ocean.

Carbon Cycle and Circulation Change in the North Pacific Ocean at the Initiation of Northern Hemisphere Glaciation Constrained by Boron‐Based Proxies in Diatoms

AbstractThe intensification of Northern Hemisphere glaciation (iNHG) at 2.73 Ma is associated with a reorganization of the subarctic Pacific Ocean and abrupt drop in opal mass accumulation rates. Uncertainty, however, remains around the extent to which these changes altered carbon dynamics and contributed to a reduction in atmospheric pCO2 and global temperatures. These issues are addressed here using the boron isotope (δ11B) proxy in diatom frustules to reconstruct past changes in the pH and pCO2 of ambient seawater. Diatom δ11B and [B] indicate a subarctic Pacific surface water increase of 0.3–0.5 pH units over the iNHG. This confirms that delivery of carbon and nutrients into surface waters was reduced at this time, explaining the drop in opal productivity and limiting CO2 outgassing from the ocean interior. We consider two hypotheses to explain this based on potential changes in circulation from the late Pliocene to early Pleistocene: “ventilation to stratification” or “stratification to ventilation.” The ventilation to stratification hypothesis, which posits a switch from vigorous Pacific Meridional Overturning Circulation in the Pliocene to stratification over iNHG, has received more attention in the literature. The stratification to ventilation hypothesis, which posits a modest increase in ventilation, is more consistent with modern and late Pleistocene analogs, the majority of models and δ13C data. These late Pliocene changes in the subarctic Pacific, in conjunction with other external and internal processes including those in the Southern Ocean, would have contributed to a lowering of atmospheric pCO2 and the long‐term expansion of ice‐sheets across the Northern Hemisphere.

Carbon-14 cycling in a nuclearized river: A first study in the downstream part of the Rhône River (France)

Carbon-14 (14C) has a natural origin but is also anthropogenically released from civil nuclear facilities. Due to its long decay period (half-life: 5700 ± 30 years), it is a persistent radionuclide in the environment. In rivers, the complex speciation of carbon makes the fate of industrial 14C difficult to track. This study reports a first overview of artificial 14C cycling in a nuclearized river. A one-year sampling campaign was conducted on the French nuclearized Rhône River and two of its non-nuclearized tributaries (Durance and Ardèche rivers). Isotopic (δ13C, Δ14C) and carbon concentrations analyses were performed on the particulate organic carbon (POC), dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC). Chlorophyll-a (Chl-a) and tritium analyses were performed to assess the dynamic of aquatic organic matter and the nuclear industry contribution, respectively. Comparisons of Δ14C data obtained from the Rhône River with those from the tributaries highlight significant industrial radiocarbon labelling in all carbon forms, with medians of 142, 130 and 42 ‰ for POC, DOC and DIC, that are 2–3 times higher than those of the tributaries. The high values of Chl-a/POC ratios with Δ14C-enriched POC suggest a biological uptake of artificial Δ14C in DIC by aquatic photosynthesis. The relationship of Δ14C-DIC with tritium activity indicates a response to recent releases and enables the contribution of nuclear power plants to be estimated at a median of 26 %. Sampling at the Rhône's mouth would reinforce our understanding of the fate of riverine 14C when entering the marine environment.

Paleoenvironmental conditions across the Coniacian-Santonian in the Kometan Formation, northeastern Iraq: Insights from planktonic foraminifera distribution, mineralogy and geochemistry

The paleoenvironmental conditions during the Coniacian-Santonian interval within the Kometan Formation in northeastern Iraq have been analyzed through the distribution of depth-related planktonic foraminifera in the carbonate rocks (limestone and marly limestone) of the Kometan Formation using standard washing method for soft samples and thin section method for hard samples supported by mineralogical investigations, geochemical analysis and stable isotopic δ13C and δ18O data. The findings indicate that saline marine waters and a hot, dry to semi-arid climate with low to medium oxygen conditions were conducive to deposition, which was characterized by high organic productivity due to marine transgression. The study revealed that the distribution of shallow water forms (SWF) of globular-shaped foraminifera, compared to deep water forms (DWF) of keeled-shaped genera, along with δ13C data from the late Turonian-early Campanian succession, indicated a relatively low sea level throughout the Late Turonian period. The water level began to rise in the early Coniacian, continuing gradually until the late Coniacian, when a noticeable increase in sea level was observed. This elevated sea level persisted through the early and late Santonian periods, before starting to drop. A slight marine transgression was noted at the beginning of the early Campanian period, followed by a significant drop in sea level. During the late Turonian, a subtropical climate prevailed. Temperature increased during the early to middle Coniacian, decreased slightly at the beginning of the late Coniacian, and then rose again at the end of the late Coniacian, indicating a shift from tropical to subtropical climatic conditions. Similar hot climatic conditions persisted in a tropical-subtropical climate during the early to late Santonian and early Campanian, with a relative temperature drop near the end of the early Campanian. No evidence of an oceanic anoxic event (OAE3) was found in the Kometan Formation during the late Coniacian–early Santonian period. The hypothesized event, based on biostratigraphy, facies analysis, stable isotopes, geochemical evidence, and field study, was limited to demonstrating an increase in the ratio of keeled chamber planktonic foraminifera compared to globular chamber ones. This ratio increase of the keeled chamber types is believed to result from a deepening sedimentary environment due to rising sea levels, creating organic matter-rich beds with high productivity and relatively low oxygen conditions during the Coniacian-Santonian boundary.

Chemostratigraphy and mineralogical characterization of Piacenzian sapropels cluster A (2.75–2.57 Ma) in the Gelasian GSSP type-section of Monte San Nicola (Sicily, Italy): Paleoenvironmental and paleogeographic implications

Mineralogical, geochemical and stable isotope (δ18O, δ13C) data from Marine Isotope Stages (MIS) G4 to 103 are here presented. The studied interval includes the sapropelic cluster A (A2-A5) from the Gelasian GSSP type-section, outcropping at Monte San Nicola (Sicily, Italy). The studied section exhibits a good response of the δ18O measured on the bulk carbonate to the Earth's astronomical parameters. The sapropelic red/brown layers (A2- A5) are alternated to grey marls and this cyclicity is clearly evident by the difference in colour, organic matter content, redox-sensitive elements and runoff indicators, tied to the precession/insolation cycles. Further, the obliquity signal is well evident in paleoproductivity indicators and mineralogical composition, driven by glacial-interglacial cycles. The obtained dataset has allowed the reconstruction of the paleoenvironmental conditions during marls/sapropels deposition, which appears to be influenced by the precessional forcing that induced strong changes in the marine water circulation. This scenario is also integrated by an original paleogeographic model including the presence of a high topographic structure in SE Sicily that limited water exchanges between the Ionian and Central Mediterranean Seas during sea level drawdowns, caused by glacial phases, triggered by obliquity minima.

Holocene hillslope evolution through extreme rainfall induced landslides in the mountainous region of Rio de Janeiro, Brazil: Geochronology and paleoenvironmental evidence

AbstractGeomorphological, geochronological and paleoenvironmental data were integrated to examine how Holocene environmental changes have influenced geomorphic responses, particularly recurrent landslides and colluvial deposition on the steep slopes of the Rio de Janeiro mountains. This study focuses on a pilot hillslope (32°) with a concave‐up topographic hollow and associated shallow translational landslides, enhancing our understanding of how extreme climatic events shaped landscape evolution in the region prior to significant human impact. Recently, the hillslope was reactivated by a shallow landslide triggered by the extreme rainfall event of January 2011, which resulted in over 3600 landslides in the region. Subsequent deep gullying exposed a deposit (>3 m) containing buried, organic‐rich colluvial layers. Comprehensive analysis was conducted on sedimentological, geochronological (AMS 14C), palynological, taphonomic and carbon isotope (δ13C) data from this deposit. The geochronological results indicate that the hillslope's evolution involves recurrent shallow translational landslides throughout the Holocene, with organic colluvial layers dating from 10 148 cal years BP at the base to 663 cal years BP at the top. Charcoal fragments of various sizes suggest frequent paleofires during the Holocene. Palynological and taphonomic analyses reveal post‐fire herbaceous‐shrubby vegetation and ferns (Asteraceae, Poaceae, Alchornea, Baccharis, Celtis and Polypodium), with predominant pollen grains and spores showing mechanical damage indicative of high transport energy and physical stress conditions. The rarefied post‐fire vegetation and pioneer forest genera identified in the deposit are associated with a hydrological and mechanical dynamics that likely created less stable conditions on the slope system, promoting the occurrence of shallow landslides throughout the Holocene.

Soil organic carbon pools as influenced by 21 years of conservation agriculture management practices in Saskatchewan

Soil organic carbon (SOC) content is a key metric of soil quality and limited work has been done to examine the effect of long-term conservation agriculture management practices (CAMP) on SOC pools within western Canadian soils. We assessed the nature and permanence of sequestered SOC within 90 diverse Saskatchewan surface (0–10 cm) agricultural soils before and after 21 years of CAMP. Comparisons were made of total SOC, labile and dynamic SOC fractions (light fraction, water-extractable, and microbial biomass), respirable CO2–C during a 6-week incubation, along with spectroscopic characterization using 13C/12C stable isotope ratio and ATR-FTIR. Among soil climatic zones, the SOC content increased in the semi-arid Brown and Dark Brown soils, ranging from 2.4 to 3.7 Mg C ha−1 (111.4–187.7 kg C ha−1 year−1), but did not change in the subhumid Black, Dark Gray, and Gray soils. Overall, soils having the smallest initial SOC level were most responsive to CAMP and accumulated more SOC. According to the δ13C data, CAMP appeared to reduce annual crop moisture stress, especially within the Brown soil zone. Decreased light fraction and water-extractable SOC contents in Black, Dark Gray, and Gray soils could reflect more intense decomposition and greater surface stratification of crop residues. Brown soils experienced the largest increase in microbial biomass-C content. The CO2–C emissions from the Brown, Dark Brown, and Gray soils under CAMP suggest greater SOC stability in 2018 compared with 1996. The ATR-FTIR data pointed to enhanced SOC persistence, via more stabilized SOC forms and mineral-associated organic C fractions.

Preadult diets in the prehistoric Lima-city: Stable isotopes from Huaca 20 (620–780 CE), Maranga Complex, Peru

Using stable isotope and Bayesian Mixing Models, this study aims to understand the preadult dietary patterns of human individuals from Huaca 20 (H20, 620–780 CE), a residential sector of the main urban center in the lower Rimac Valley of the Peruvian Central Coast. Due to preservation issues, a practical approach was employed to understand the diet of this population, using data for δ13C and δ15N obtained from the dentine of anatomic tooth segments of 20 adult individuals, which were analyzed by sex and broad life-stages (i.e., infant, child, adolescent). We then conducted individual paleodietary reconstructions using a Bayesian Mixing Model to obtain the quantitative contribution of four food groups. The results indicate that this population relied on a mixed diet mainly composed of C4 (maize) and C3 resources complemented with marine protein in variable proportions, and minimal contributions of terrestrial protein. Maize and C3 resources were the main foods during infancy and childhood of these adults, whereas the diet during adolescence shows more marine protein, possibly more similar to the adult diet of this community. This isotopic evidence from Huaca 20 suggests the use of specific infant feeding strategies.

Preliminary isotopic assessment of weaning in bonobos shows evidence for extended nursing, sibling competition and invested first-time mothers.

Although considered a hallmark in early ontogeny, weaning from breastmilk is difficult to monitor in wild primates and weaning ages remain unknown for wild bonobos (Pan Paniscus). Here, we calculated inter-birth intervals from demographic data and measured the isotopic offsets (Δ15N and Δ13C) between mother (n = 17) and offspring (n = 28) fecal sample pairs (n = 131, total n = 246) in the LuiKotale bonobos to assess nutritional weaning for the first time. We tested the effects of infant age, female parity, and sibling competition on Δ15N and Δ13C values. We found bonobo inter-birth intervals ranging from 2.2 to 7.3 years (x̄ = 4.7 ± 1.3 years) at LuiKotale. The Δ15N and Δ13C values suggested nutritional weaning on average by 6.6 and 7.0 years of age respectively, considerably exceeding weaning ages reported for chimpanzees (P. troglodytes) using the same approach. Our Δ13C data suggested that the number of offspring present affected nursing, with first-time mothers nursing more and possibly longer. The Δ15N and Δ13C values decreased with the arrival of the next sibling, suggesting sibling competition reduces milk access. Nevertheless, offspring may continue nursing 2.5-3 years after the birth of the next sibling, corresponding well with observations on low infant mortality. In conclusion, bonobo mothers provide remarkably enduring materna l support in the form of nursing concurrently to several offspring.

Compound-specific radiocarbon analysis of sedimentary fatty acids: Potential as a dating tool for lake sediments of Mt. Fuji volcanic region, Japan

Compound-specific radiocarbon analysis (CSRA) is a promising tool for dating sediment sequences where traditional dating methods are impractical. However, the applicability of CSRA of short-chain fatty acids as a dating tool remains poorly understood, especially in lacustrine settings. Accordingly, we determined the radiocarbon content (Δ14C) of individual fatty acids in sediments of Lake Yamanaka (central Japan), as well as their stable carbon and hydrogen isotope ratios, to evaluate the potential of CSRA as a dating tool in volcanic lake environments. We found that the Δ14C values of plant-derived (C24, C26, and C28) n-fatty acids (–99‰ to –149‰) were considerably lower than the Δ14C of charred plants (139‰) within the sediments and those of living aquatic plants (–52‰ to –58‰) in Lake Yamanaka, suggesting that contributions from pre-aged terrestrial and aquatic plant materials likely affect these acids. Similarly, the Δ14C of C16n-fatty acid (–95‰) in surface sediments was much lower than the Δ14C of modern aquatic plants (–52‰ to –58‰), as well as the Δ14C of dissolved organic carbon (DIC) in surface water (–48‰). Together with the stable isotope results, we conclude that in addition to autochthonous aquatic sources, contributions from pre-aged terrestrial carbon sources significantly affect the Δ14C of C16n-fatty acids. Comparing fatty acid Δ14C and concentration data across lakes within the Mt. Fuji region suggests that CSRA of the C16 acid provides valid chronological information only when the C16 originates exclusively from autochthonous aquatic sources, with minor allochthonous terrestrial input.

EATING LIKE THE ELITE AT NEO‐PALATIAL KNOSSOS

SummaryDiachronic research of social status differences in diet reveals a dynamic interplay of cultural, economic, and technological forces that have shaped the food choices of individuals across the past centuries. In this paper we focus on food and related practices at Palatial Knossos on Crete in the mid‐second millennium BC and review palaeodietary stable carbon and nitrogen isotope (δ13C and δ15N) data from two cemeteries to explore evidence for embodied social variation during the site’s uncontested heyday in the Neo‐palatial Period (c.1700 to 1500 BC). We show that analysis by sex and tomb suggests no significant social differentiation in access to food resources. Instead, temporal trends reveal increased availability of animal protein during the Neo‐palatial period, aligning with Knossos' political and economic supremacy. We argue that the equitable living circumstances at Knossos during the Neo‐palatial period may have contributed to the absence of factional competition and social unrest, potentially explaining the site's continuity into Post‐palatial times despite widespread destructions elsewhere on Crete. Overall, the findings shed light on the complex interplay between diet, social structure, and historical context at Neo‐palatial Knossos.

Shallow ocean deoxygenation drove trilobite turnover during the late Cambrian SPICE event

The spread of marine anoxia is believed to have played a key role in the development of the SPICE (Steptoean Positive Carbon Isotope Excursion) event and the end-Marjuman extinction in the late Cambrian (∼497.5 m.y. ago), but their cause-and-effect relationship is poorly constrained. Here we present an integrated analysis of carbonate δ13C, cerium anomalies (Ce/Ce*), and genus-level diversity data of trilobites from the North China Platform. Our results show tightly coupled changes between the SPICE, an increase in Ce/Ce*, and a trilobite turnover event, which we interpret as indicating enhanced productivity and organic remineralization, leading to the development of low-oxygen conditions in shallow-water settings. This study therefore establishes a direct link between local ecological stress and trilobite turnover during the global SPICE event. Furthermore, the presence of low-oxygen rather than fully anoxic conditions during the peak of the SPICE event could explain the nature of the end-Marjuman crisis, which was characterized by the replacement of shallow-water fauna by deeper-water counterparts that were potentially more tolerant of hypoxia.

Nature and occurrence, geochemical characteristics, and families of the crude oils in Sirt Basin, Libya: Implication for super rift basin petroleum system

In this study, we investigated the nature and characteristics of petroleum fluids in a super-global basin situated in the central north of Libya. With over 100 discovered fields (comprising oil and gas), this study aimed to understand the basin's petroleum accumulation mechanism (PAM), thereby shedding light on the factors contributing to significant petroleum discoveries in North Africa (Libya). The primary objective of this study was to provide a detailed regional refined oil family distribution and new insights into the total petroleum system (TPS) of the basin. This analysis was based on the integration of regional geology and organic geochemistry. Additionally, we utilized the physical properties of petroleum, such as API and sulphur content (%S), to obtain a better understanding of the regional physical nature of petroleum types and properties. Organic geochemical data for the basin fields were compiled, focusing on key biological marker and carbon isotope (‰ δ13C) data for saturated and aromatic compounds. These data were used to understand the origin, depositional source, and thermal maturity of the generated, migrated, and accumulated petroleum fluids. The study established specific types of organofacies and their relationships with petroleum phase characteristics, including type and quality, categorized into known groups (e.g., B, C, and D/E). Hierarchical cluster analysis (HCA) and map-based presentation approaches were used to determine the spatial types and distributions of oil and gas families in the basin. This was achieved by selecting the input parameters from various datasets and defining the significant parameters to characterize the distribution patterns. The findings indicate that the bulk fluid of the Sirt Basin primarily resembled Brent oil, which was characterized by a very low sulphur content (less than 1.4%). The API gravity ranged from 30 to 65, reflecting a diverse range of oil types within the basin. The crude oils in the basin were primarily derived from marine organofacies, predominantly from type B. This inference is supported by related biomarkers such as regular steranes and isoprenoids. Furthermore, the analysis of carbon isotopes provided a similar indication, with values ranging from −32 to −27 for ‰ δ13C for saturates and −31.2 to −25.4 ‰ δ13C for aromatic compounds. The thermal maturity biomarker ratio (Ts/Ts + Tm) of the Sirt Basin crude oils varied from 0.35 to 0.92, suggesting different levels of thermal maturity, typically ranging from the mid to late mature stages. This observation is consistent with the indication based on the 22S/22S + 22R ratio. The basin exhibited four dominant oil families and eight subfamilies with the same geochemical characteristics (HCA-based analysis), including early and later generations, relatively sulphurized oils, and condensate families.

Interpreting life-history traits, seasonal cycles, and coastal climate from an intertidal mussel species: Insights from 9000 years of synthesized stable isotope data.

Understanding past coastal variability is valuable for contextualizing modern changes in coastal settings, yet existing Holocene paleoceanographic records for the North American Pacific Coast commonly originate from offshore marine sediments and may not represent the dynamic coastal environment. A potential archive of eastern Pacific Coast environmental variability is the intertidal mussel species Mytilus californianus. Archaeologists have collected copious stable isotopic (δ18O and δ13C) data from M. californianus shells to study human history at California's Channel Islands. When analyzed together, these isotopic data provide windows into 9000 years of Holocene isotopic variability and M. californianus life history. Here we synthesize over 6000 δ18O and δ13C data points from 13 published studies to investigate M. californianus shell isotopic variability across ontogenetic, geographic, seasonal, and millennial scales. Our analyses show that M. californianus may grow and record environmental information more irregularly than expected due to the competing influences of calcification, ontogeny, metabolism, and habitat. Stable isotope profiles with five or more subsamples per shell recorded environmental information ranging from seasonal to millennial scales, depending on the number of shells analyzed and the resolution of isotopic subsampling. Individual shell profiles contained seasonal cycles and an accurate inferred annual temperature range of ~ 5°C, although ontogenetic growth reduction obscured seasonal signals as organisms aged. Collectively, the mussel shell record reflected millennial-scale climate variability and an overall 0.52‰ depletion in δ18Oshell from 8800 BP to the present. The archive also revealed local-scale oceanographic variability in the form of a warmer coastal mainland δ18Oshell signal (-0.32‰) compared to a cooler offshore islands δ18Oshell signal (0.33‰). While M. californianus is a promising coastal archive, we emphasize the need for high-resolution subsampling from multiple individuals to disentangle impacts of calcification, metabolism, ontogeny, and habitat and more accurately infer environmental and biological patterns recorded by an intertidal species.

RADIOCARBON VARIATIONS IN ANNUAL TREE RINGS WITH 11-YEAR SOLAR CYCLES DURING 1800–1950

ABSTRACT The results of radiocarbon variation studies observed in annual tree rings from the NW Pacific (USA Northwest) (Stuiver and Braziunas 1993) and Europe (England, Brehm et al. 2021; Slovakia, Povinec 1977, 1987) are reviewed with the aim of better understanding the 11-year radiocarbon cycle and possible impacts of solar proton events on 14C levels in the atmosphere and biosphere. The average Δ14C amplitude in tree rings for the period of 1798–1944 was 1.3 ± 0.3‰, the average periodicity was 11 ± 1 years, and the average time shift between the sunspot numbers and Δ14C records was 3 ± 1 years. A new solar activity minimum (Gleissberg minimum, 1878–1933) has been identified in the Δ14C data sets from the NW Pacific and England, showing Δ14C excess of 7‰, comparable to the Dalton minimum (1797–1823). No significant changes in Δ14C levels were identified that could be associated with solar proton events during 1800–1950.

Impact of thinning on leaf economics, plant hydraulics, and growth dynamics

Integrating climate change concerns into forest management strategies remains challenging. Among management strategies, thinning has been proven to alter major components underlying the carbon and water cycles over the short term. However, the functional adaptability of managed forests to cope with long-term drought remains unclear. This study aims to quantify the influence of thinning on key plant functional traits for two pine species, and their impacts on the fundamental processes of tree growth and transpiration. We conducted an experimental silvicultural trial with varying thinning intensities in two Pinus sylvestris and Pinus nigra plantations with the following specific objectives: i) to assess the impact of thinning on major traits involved in the leaf economic spectrum (LES), and hydraulic relations, and ii) to understand which of these traits reflect fundamental aspects of plant growth and transpiration, and their relations with environment. We used a combination of dendrochronological (basal area increment, BAI), sapflow (Fd), and tree ring isotope (δ13C) data, along with key functional and physiological traits including photosynthesis (A), leaf mass area (LMA), Huber value (Hv), sapwood density (Wd), and predawn to midday water potential (Ψpd, Ψmd).Our results revealed species-specific responses, with P. nigra exhibiting a conservative growth strategy, whereas P. sylvestris displayed increased growth after thinning. Despite thinning influenced both BAI and wood δ13C with notable species-dependent variations, we evidenced a general convergence in the relationships between LES traits and Hv across species, treatments and seasons (p < 0.01). BAI responses to thinning translated into predictable changes in key hydraulic traits and adaptive changes in physiological performance. For instance, BAI was inversely related to LMA and Hv. Consistent with LES, variations in LMA influenced A. In turn, seasonal variations in LMA scaled negatively with Ψpd, and Ψmd (p < 0.01). Such a functional adaptation suggests that thinning promotes growth while favouring forest resilience in the long term. This study provides practical implications for the implementation of a trait-based approach into silvicultural frameworks and anticipating the consequences of climate change for managed forest ecosystems.

Spatial ecology of moose in Sweden: Combined Sr-O-C isotope analyses of bone and antler.

The study of spatial (paleo)ecology in mammals is critical to understand how animals adapt to and exploit their environment. In this work we analysed the 87Sr/86Sr, δ18O and δ13C isotope composition of 65 moose bone and antler samples from Sweden from wild-shot individuals dated between 1800 and 1994 to study moose mobility and feeding behaviour for (paleo)ecological applications. Sr data were compared with isoscapes of the Scandinavian region, built ad-hoc during this study, to understand how moose utilise the landscape in Northern Europe. The 87Sr/86Sr isoscape was developed using a machine-learning approach with external geo-environmental predictors and literature data. Similarly, a δ18O isoscape, obtained from average annual precipitation δ18O values, was employed to highlight differences in the isotope composition of the local environment vs. bone/antler. Overall, 82% of the moose samples were compatible with the likely local isotope composition (n = 53), suggesting that they were shot not far from their year-round dwelling area. 'Local' samples were used to calibrate the two isoscapes, to improve the prediction of provenance for the presumably 'non-local' individuals. For the latter (n = 12, of which two are antlers and ten are bones), the probability of geographic origin was estimated using a Bayesian approach by combining the two isoscapes. Interestingly, two of these samples (one antler and one bone) seem to come from areas more than 250 km away from the place where the animals were hunted, indicating a possible remarkable intra-annual mobility. Finally, the δ13C data were compared with the forest cover of Sweden and ultimately used to understand the dietary preference of moose. We interpreted a difference in δ13C values of antlers (13C-enriched) and bones (13C-depleted) as a joint effect of seasonal variations in moose diet and, possibly, physiological stresses during winter-time, i.e., increased consumption of endogenous 13C-depleted lipids.