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To this date, the extent of microbial biodegradation of plastics is still an open question. The presence of hydrocarbon degraders as part of the plastisphere identified from marine plastic debris (MPD) samples has prompted different ideas about the role of such a group of microorganisms in the degradation of these synthetic polymers. In this investigation, we have tested the potential of the hydrocarbonoclastic bacteria Alcanivorax sp. 24 (bacterial isolate obtained from MPD) to degrade polyethelene (PE) –one of the most recalcitrant carbon-based synthetic materials produced and, currently, the most ubiquitous plastic pollutant found in nature. Evidence indicates that an array of abiotic and biotic processes eventually breaks down PE. However, the biological impact and mechanistic understanding of the process are unclear. Here, using high-throughput proteomics, we investigated the molecular processes that take place in the hydrocarbon-degrading marine bacterium Alcanivorax sp. 24 when grown in the presence of low-density PE (LDPE). As well as efficiently utilising and assimilating the leachate of weathered LDPE, the bacterium was able to reduce the molecular weight distribution and overall mass of pristine LDPE films (0.9 % after 34 days of incubation). Most interestingly, Alcanivorax acquired the isotopic signature of the pristine plastic and induced an extensive array of metabolic pathways for aliphatic compound degradation. Presumably, the primary biodegradation of LDPE by Alcanivorax sp. 24 is possible via the production of extracellular reactive oxygen species as observed both by the material's surface oxidation and the measurement of superoxide in the culture with LDPE. Our findings confirm that hydrocarbon-biodegrading bacteria within the plastisphere may in fact have a role in degrading PE. Also see: https://micro2022.sciencesconf.org/427350/document, In MICRO 2022, Online Atlas Edition: Plastic Pollution from MACRO to nano

Fluvial sediments are important archives of paleoenvironments. However, variations in sediment production and transport processes greatly influence sediment geochemistry and resultant interpretations of ancient conditions. Tectonically-active tropical regions are particularly sensitive to climate feedbacks because these areas are often characterized by high precipitation rates, rapid erosion and short sediment residence times. We analyzed the hydrogen and carbon isotope composition of plant-derived n-alkanes (δ2Hn-alkane and δ13Cn-alkane) in sediment cores along the Gaoping River-submarine canyon system in southwestern Taiwan to examine climatic and geomorphic controls on isotope geochemical signatures of fluvial sedimentary archives. These records span the last ∼26 kyr and provide critical insight into the temporal and spatial variations in sedimentary biomarker isotopes within a source-to-sink system. Isotope data are coupled with new results from an iCESM 1.2 Earth System Model of precipitation isotopes during the last glacial-interglacial cycle. Biomarker isotope and modeling results support two important conclusions. First, biomarker isotope values change by ∼10 to 15‰ in δ2Hn-alkane and ∼1 to 2‰ δ13Cn-alkane in offshore SW Taiwan through the late Quaternary deglaciation. These shifts are consistent with iCESM predictions and other records from the South China Sea and are best explained by a shift in isotope hydrology due to regional warming and biologic responses to increased atmospheric pCO2. Second, the δ2Hn-alkane of biomarkers preserved in onshore sediments proximal to the mountain range is ∼15 to 20‰ more negative than biomarkers deposited in offshore sites, and the temporal change in carbon isotopes exceeds that observed in the offshore deposits. The onshore core locality is proximal to the orogen and characterized by a mean elevation > 1 km compared to the offshore site, which has a mean catchment elevation of ∼500 m. These data show that depositional setting and catchment hypsometry strongly bias the geochemical signature of sediments transported through the river system. The magnitude of isotopic variability generated by catchment geometry and sediment integration greatly exceeds the change associated with warming during deglaciation. This result suggests that catchment integration processes may play a similar or larger role in shaping fluvial geochemical records in tropical mountain systems than climatic factors.

The carbon isotopic composition of plant wax n-alkanes (δ13Cn-alkane) is a well-established proxy for bulk plant δ13C, which itself reflects plant community composition and palaeohydrology in the geologic record. Although the biosynthetic processes which form n-alkanes cause a depletion in 13C relative to bulk plant tissue, it is generally presumed that this depletion is constant. In particular, on geologic timescales bulk plant δ13C is invariant to changes in atmospheric CO2, and it is therefore assumed that δ13Cn-alkane follows the same pattern. However, this assumption has not been tested, and it is possible that the biosynthetic fractionation during the formation of n-alkanes and other lipid biomarkers is affected by atmospheric CO2 concentration independently of trends in bulk plant tissue. Here, I use the Birmingham Institute of Forest Research (BIFoR)’s Free Air Carbon Enrichment experiment (FACE) to investigate the impact of elevated CO2 on both bulk and n-alkane δ13C in order to identify any such influence of elevated CO2 on n-alkane isotopic composition. If any such effects are detected, CO2 levels should be accounted for in interpretations of deep-time δ13Cn-alkane records.

The Antarctic coastal zone is an area of high primary productivity, particularly within coastal polynyas, where large phytoplankton blooms and drawdown of CO2 occur. Reconstruction of historical primary productivity changes and the associated driving factors could provide baseline insights on the role of these areas as sinks for atmospheric CO2, especially in the context of projected changes in coastal Antarctic sea ice. Here we investigate the potential for using carbon isotopes (δ13C) of fatty acids in marine sediments as a proxy for primary productivity. We use a highly resolved sediment core from off the coast of Adélie Land spanning the last ∼ 400 years and monitor changes in the concentrations and δ13C of fatty acids along with other proxy data from the same core. We discuss the different possible drivers of their variability and argue that C24 fatty acid δ13C predominantly reflects phytoplankton productivity in open-water environments, while C18 fatty acid δ13C reflects productivity in the marginal ice zone. These new proxies have implications for better understanding carbon cycle dynamics in the Antarctica coastal zone in future palaeoclimate studies.

The Antarctic coastal zone is an area of high primary productivity, particularly within coastal polynyas where large phytoplankton blooms and drawdown of CO2 occur. Reconstruction of historical primary productivity changes, and the associated driving factors, could provide baseline insights on the role of these areas as sinks for atmospheric CO2, especially in the context of projected changes in coastal Antarctic sea ice. Here we investigate the potential for using carbon isotopes (δ13C) of fatty acids in marine sediments as a proxy for primary productivity. We use a highly resolved sediment core from off the coast of Adélie Land spanning the last ~ 400 years and monitor changes in the concentrations and δ13C of fatty acids along with other proxy data from the same core. We discuss the different possible drivers of their variability and argue that C24 fatty acid δ13C predominantly reflects phytoplankton productivity in open water environments, while C18 fatty acid δ13C reflects productivity in the marginal ice zone. These new proxies have implications for better understanding carbon cycle dynamics in the Antarctica coastal zone in future paleoclimate studies.

The invention of pottery was a fundamental technological advancement with far-reaching economic and cultural consequences. Pottery containers first emerged in East Asia during the Late Pleistocene in a wide range of environmental settings, but became particularly prominent and much more widely dispersed after climatic warming at the start of the Holocene. Some archaeologists argue that this increasing usage was driven by environmental factors, as warmer climates would have generated a wider range of terrestrial plant and animal resources that required processing in pottery. However, this hypothesis has never been directly tested. Here, in one of the largest studies of its kind, we conducted organic residue analysis of >800 pottery vessels selected from 46 Late Pleistocene and Early Holocene sites located across the Japanese archipelago to identify their contents. Our results demonstrate that pottery had a strong association with the processing of aquatic resources, irrespective of the ecological setting. Contrary to expectations, this association remained stable even after the onset of Holocene warming, including in more southerly areas, where expanding forests provided new opportunities for hunting and gathering. Nevertheless, the results indicate that a broader array of aquatic resources was processed in pottery after the start of the Holocene. We suggest this marks a significant change in the role of pottery of hunter-gatherers, corresponding to an increased volume of production, greater variation in forms and sizes, the rise of intensified fishing, the onset of shellfish exploitation, and reduced residential mobility.

We conducted a series of heating experiments using pure n -alkane mixtures and natural soil organic extracts to evaluate isotopic and molecular changes during cracking and exchange associated with thermal alteration. Experiments included controlled heating of pure n- alkane mixtures (C 7 –C 40 ) and a total lipid extract from a modern wetland sediment under both ambient air and anhydrous, closed-system conditions. In an argon-purged, closed-system (at temperatures of 60–300 °C), the distribution of pure n- alkane mixtures predictably shifted towards a higher proportion of shorter chain lengths ( 20 ), with no odd-over-even preference. During the heating process, the δ 2 H values of long-chain n -alkanes (> C 20 ) became 2 H-enriched by up to 12‰, while the δ 2 H of short chain n -alkanes were 2 H-depleted by up to 28‰. When repeating these experiments with the total lipid extract from soils, we observed 2 H-enrichment of individual n -alkanes and mean-weighted δ 2 H n C27–31 of soil n- alkanes under both ambient air (up to 15‰ at 300 °C over 72 h) and Ar-purged, anhydrous, closed-system (up to 10‰ at 300 °C over 720 h) conditions. Carbon preference indices (CPI) decreased during the thermal alteration process in tandem with isotopic changes. The average chain length (ACL) of the n -alkanes decreased by more than 1 unit during heating, even at temperatures as low as 60 °C, when in the ambient air. This highlights the potential for differences in sediment lithology and gas permeability on an outcrop scale to alter primary organic signatures during thermal alteration. In the presence or absence of oxygen, the hydrogen isotopic composition of pure n- alkane mixtures and natural extracts change from the original composition, though for most compounds this was less than 10–15‰ at temperatures below 150 °C. The magnitude of change is greatest for shorter chain n -alkanes and at temperatures above 150 °C. We conclude that degradation and/or production during heating, such as may be expected during sediment burial or contact heating, could drive shifts in the measured hydrogen isotope composition of sedimentary leaf wax biomarkers. This is especially rapid at temperatures in excess of 200 °C, but the magnitude of isotopic change is generally in the range 10–15‰ before the loss of compounds reaches levels that are below analytical relevance for isotope work. Collectively, our results highlight the need for careful consideration of the depositional environment (particularly for information pertaining to oxygen availability) when interpreting molecular and/or isotopic information from sedimentary alkanes. In addition, they also demonstrate the general fidelity of hydrogen isotopes of n -alkanes under shallow burial temperatures with only modest isotopic enrichment prior to complete loss of long carbon chain compounds.

The early Eocene (56 to 48 million years ago) is inferred to have been the most recent time that Earth's atmospheric CO2 concentrations exceeded 1000 ppm. Global mean temperatures were also substantially warmer than present day. As such, study of early Eocene climate provides insight into how a super-warm Earth system behaves and offers an opportunity to evaluate climate models under conditions of high greenhouse gas forcing. The Deep Time Model Intercomparison Project (DeepMIP) is a systematic model-model and model-data intercomparison of three early Paleogne time slices: latest Paleocene, Paleocene-Eocene thermal maximum and early Eocene climatic optimum. A previous article outlined the model experimental design for climate model simulations. In this article, we outline the methodologies to be used for the compilation and analysis of climate proxy data, primarily proxies for temperature and CO2. This paper establishes the protocols for a concerted and coordinated effort to compile the climate proxy records across a wide geographic range. The resulting climate atlas will be used to constrain and evaluate climate models for the three selected time intervals, and provide insights into the mechanisms that control these warm climate states. We provide version 0.1 of this database, in anticipation that this will be expanded in subsequent publications.

The Early Jurassic break-up of Pangea and the formation of the Central Atlantic Ocean are associated with changes to the atmosphere, climate, and environment, as recorded in marine carbonates from the western Tethys Ocean. However, the expression of these global changes in terrestrial successions is less well known. To better understand terrestrial-response, we investigated organic carbon isotope composition (δ13Corg), weathering trends and geochemistry in Lower Jurassic lacustrine strata in the Qaidam Basin, China, on the northern margin of the eastern Tethys Ocean. Four negative δ13Corg carbon isotope excursions are identified in lacustrine black shales during the Pliensbachian to early Toarcian stages. These negative excursions correspond to the early Pliensbachian Warming Interval, the Subnodonus Negative Event at the beginning of the late Pliensbachian, the Pliensbachian–Toarcian Boundary Event, and the early Toarcian Oceanic Anoxia Event (T-OAE), respectively, well documented in western Tethys Ocean successions. In our terrestrial successions from the Qaidam Basin, the first three events occurred under relatively warm and humid climates associated with enhanced weathering, lake transgression, and the prevalence of swamp environments. In contrast, the T-OAE was a period of intense warming and arid climate, expressed by the deposition of red beds, a hiatus in coal deposition, a sharp reduction in plant diversity, and a floristic turnover in palynoflora. Our findings show that each negative excursion is associated with peaks in mercury and nickel concentrations, supporting the hypothesis that magma intrusion into organic-rich rocks and accompanying the volcanic eruption was responsible.

Much of our existing knowledge of Middle Jurassic paleoclimate is based on well-dated marine isotopic records that show fluctuations between warm (greenhouse effected) and cool climates. In contrast, much less is known from contemporaneous terrestrial deposits that are often difficult to correlate stratigraphically with marine successions, and are typically considered as showing regional rather than global signals. In this paper we show that the carbon-isotopic, petrological and floral record through 20 m thick coals in the Northern Qaidam Basin (NW, China) represents a relatively comprehensive northern hemisphere Bajocian (Middle Jurassic) record for terrestrial climatic change. δ13Ccoal values for 88 samples from the Yuqia area in Northern Qaidam Basin range from–25.3‰ to –22.5‰, indicating that C3 plants were the main coal-forming vegetation in the region during the Middle Jurassic. This isotopic variation follows fluctuations in the composition of ferns and gymnosperms, where higher ratios correspond to more negative δ13C values. The similar carbon isotope values of gymnosperms and coal from the Yuqia area indicate that the coal comprises a high proportion of organic material derived from gymnosperm taxa, which is consistent with the very high abundance of diterpenoids in coal and especially pimarane and abietane that are produced primarily by gymnosperms. Results from the coal matrix provide an opportunity to record paleoclimate changes, showing several striking and regular coal-forming cycles with distinct long- and short-term variations. Trends of δ13Ccoal values changes coupled with the evolution of coal-forming plants may record a gradual increase in paleo-CO2 (pCO2) concentration, water-table level changes and the decrease in abundance of Classopollis conifer pollen through Bajocian. This result is in accordance with the published marine carbonate records for this time, with correlation enabled through matching carbon isotope curves from the terrestrial succession at Yuqia and marine records. The similarity of the terrestrial and marine geochemical and floral record is an indication that the observed paleoclimate signal is a global phenomenon. Furthermore, the high-frequency fluctuation of δ13Ccoal values, along with the coal petrologic variations may record short-term changes of environmental factors (e.g. temperature or humidity/precipitation), especially during intervals when palaeobotanical composition has not fluctuated intensely.

Estimates of atmospheric moisture are critical for understanding the links and feedbacks between atmospheric CO2 and global climate. At present, there are few quantitative moisture proxies that are applicable to deep time. We present a new proxy for atmospheric moisture derived from modern climate and leaf biomarker data from North and Central America. Plants have a direct genetic pathway to regulate the production of lipids in response to osmotic stress, which is manifested in a change in the distribution of simple aliphatic lipids such as n-alkanes. The Average Chain Length (ACL) of these lipids is therefore statistically related to mean annual vapor pressure deficit (VPDav), enabling quantitative reconstruction of VPD from sedimentary n-alkanes. We apply this transfer function to the Armantes section of the Calatayud-Daroca Basin in Central Spain, that spans the Middle Miocene Climatic Optimum (MMCO) and the Middle Miocene Climate Transition (MMCT). Reconstructed VPDav rises from 0.13 to 0.92 kPa between 16.5 and 12.4 Ma, indicating a substantial drying through the MMCT. These data are consistent with fossil assemblages and mammalian stable isotope data, highlighting the utility of this new organic molecular tool for quantifying hydrologic variability over geologic timescales.

Carbon isotope measurements of individual fatty acids (C16:0 and C18:0) recovered from archaeological pottery vessels are widely used in archaeology to investigate past culinary and economic practices. Typically, such isotope measurements are matched with reference to food sources for straightforward source identification, or simple linear models are used to investigate mixing of contents. However, in cases where multiple food sources were processed in the same vessel, these approaches result in equivocal solutions. To address this issue, we tested the use of a Bayesian mixing model to determine the proportional contribution of different food sources to a series of different mixed food compositions, using data generated both by simulation and by experiment. The model was then applied to previously published fatty acid isotope datasets from pottery from two prehistoric sites: Durrington Walls, near Stonehenge in southern Britain and Neustadt in northern Germany. We show that the Bayesian approach to the reconstruction of pottery use offers a reliable probabilistic interpretation of source contributions although the analysis also highlights the relatively low precision achievable in quantifying pottery contents from datasets of this nature. We suggest that, with some refinement, the approach outlined should become standard practice in organic residue analysis, and also has potential application to a wide range of geological and geochemical investigations.

Interpretation of sedimentary n-alkyl lipid d2H data is complicated by a limited understanding of factors controlling interspecies variation in biomarker 2H/1H composition. To distinguish between the effects of interrelated environmental, physical and biochemical controls on the hydrogen isotope composition of n-alkyl lipids, we conducted linked d2H analyses of soil water, xylem water, leaf water and n-alkanes from a range of C3 and C4 plants growing at a UK saltmarsh (i) across multiple\ud sampling sites, (ii) throughout the 2012 growing season, and (iii) at different times of the day. Soil waters varied isotopically by up to 35& depending on marsh sub-environment, and exhibited site-specific seasonal shifts in d2H up to a maximum of 31 per mil. Maximum interspecies variation in xylem water was 38 per mil, while leaf waters differed seasonally by a maximum of 29 per mil. Leaf wax n-alkane 2H/1H, however, consistently varied by over 100 per mil throughout the 2012 growing season, resulting in an interspecies range in the ewax/leaf water values of -79 per mil to –227 per mil. From the discrepancy in the magnitude of these isotopic differences, we conclude that mechanisms driving variation in the 2H/1H composition of leaf water, including (i) spatial changes in soil water 2H/1H, (ii) temporal changes in soil water 2H/1H, (iii) differences in xylem water 2H/1H, and (iv) differences in leaf water evaporative 2H-enrichment due to varied plant life forms, cannot explain the range of n-alkane d2H values we observed. Results from this study suggests that accurate reconstructions of palaeoclimate regimes from sedimentary n-alkane d2H require further research to constrain those biological mechanisms influencing species-specific differences in 2H/1H fractionation during lipid biosynthesis, in particular where plants have developed biochemical adaptations to water-stressed conditions. Understanding how these mechanisms interact with environmental conditions will be crucial to ensure accurate\ud interpretation of hydrogen isotope signals from the geological record.

Analysis of organic residues in pottery vessels has been successful in detecting a range of animal and plant products as indicators of food preparation and consumption in the past. However, the identification of plant remains, especially grain crops in pottery, has proved elusive. Extending the spectrum is highly desirable, not only to strengthen our understanding of the dispersal of crops from centres of domestication but also to determine modes of food processing, artefact function and the culinary significance of the crop. Here, we propose a new approach to identify millet in pottery vessels, a crop that spread throughout much of Eurasia during prehistory following its domestication, most likely in northern China. We report the successful identification of miliacin (olean-18-en-3β-ol methyl ether), a pentacyclic triterpene methyl ether that is enriched in grains of common/broomcorn millet (Panicum miliaceum), in Bronze Age pottery vessels from the Korean Peninsula and northern Europe. The presence of millet is supported by enriched carbon stable isotope values of bulk charred organic matter sampled from pottery vessel surfaces and extracted n-alkanoic acids, consistent with a C4 plant origin. These data represent the first identification of millet in archaeological ceramic vessels, providing a means to track the introduction, spread and consumption of this important crop.

The carbon isotope composition of terrestrial plants records valuable ecophysiological and palaeoecological information. However, interspecies variability in 13C/12C, at both the bulk and compound-specific (CS) level, requires further exploration across a range of ecosystem types. Here, we present bulk and n-alkane δ13C values, and n-alkane concentrations, from seven plants (C3 and C4) growing in a temperate UK saltmarsh. Inter- and intra-species variation in n-alkane δ13C values among C3 plants ranged from 8‰ (n-C31) to 10‰ (n-C27) across the 2011 and 2012 growing seasons, exceeding variability in bulk tissue (7‰). In contrast, the C4 monocot showed < 2‰ seasonal shifts in bulk and CS values. As a result of the variability in our CS data, we calculate that n-alkane based C3/C4 reconstructions in temperate saltmarshes have a maximum uncertainty of ∼11%. For dicots and succulents, seasonal bulk and CS δ13C trends diverged, while for C3 and C4 monocots, bulk and CS values followed similar temporal patterns. Fractionation between bulk and n-alkane carbon isotope values varied from −4 to −10‰ for C3 plants, and reached −13‰ for the C4 monocot. We explain discrepancies between bulk and n-alkane δ13C values by referring to possible interspecies variation in salinity adaptation, which may influence the partitioning of pyruvate, shifting the isotopic composition of lipid biomarkers. These findings open new avenues for empirical studies to further understand the metabolic processes fractionating carbon during the synthesis of n-alkanes, enhancing interpretation of the biomarker signal from the geological record.

The earliest pots in the world are from East Asia and date to the Late Pleistocene. However, ceramic vessels were only produced in large numbers during the warmer and more stable climatic conditions of the Holocene. It has long been assumed that the expansion of pottery was linked with increased sedentism and exploitation of new resources that became available with the ameliorated climate, but this hypothesis has never been tested. Through chemical analysis of their contents, we herein investigate the use of pottery across an exceptionally long 9,000-y sequence from the Jomon site of Torihama in western Japan, intermittently occupied from the Late Pleistocene to the mid-Holocene. Molecular and isotopic analyses of lipids from 143 vessels provides clear evidence that pottery across this sequence was predominantly used for cooking marine and freshwater resources, with evidence for diversification in the range of aquatic products processed during the Holocene. Conversely, there is little indication that ruminant animals or plants were processed in pottery, although it is evident from the faunal and macrobotanical remains that these foods were heavily exploited. Supported by other residue analysis data from Japan, our results show that the link between pottery and fishing was established in the Late Paleolithic and lasted well into the Holocene, despite environmental and socio-economic change. Cooking aquatic products in pottery represents an enduring social aspect of East Asian hunter-gatherers, a tradition based on a dependable technology for exploiting a sustainable resource in an uncertain and changing world.