Lombards on the Move – An Integrative Study of the Migration Period Cemetery at Szólád,Hungary

In 2005 to 2007 45 skeletons of adults and subadults were excavated at the Lombard period cemetery at Szólád (6^th century A.D.), Hungary. Embedded into the well-recorded historical context, the article presents the results obtained by an integrative investigation including anthropological, molecular genetic and isotopic (δ¹⁵N, δ¹³C, ⁸⁷Sr/⁸⁶Sr) analyses. Skeletal stress markers as well as traces of interpersonal violence were found to occur frequently. The mitochondrial DNA profiles revealed a heterogeneous spectrum of lineages that belong to the haplogroups H, U, J, HV, T2, I, and K, which are common in present-day Europe and in the Near East, while N1a and N1b are today quite rare. Evidence of possible direct maternal kinship was identified in only three pairs of individuals. According to enamel strontium isotope ratios, at least 31% of the individuals died at a location other than their birthplace and/or had moved during childhood. Based on the peculiar ⁸⁷Sr/⁸⁶Sr ratio distribution between females, males, and subadults in comparison to local vegetation and soil samples, we propose a three-phase model of group movement. An initial patrilocal group with narrower male but wider female Sr isotope distribution settled at Szólád, whilst the majority of subadults represented in the cemetery yielded a distinct Sr isotope signature. Owing to the virtual absence of Szólád-born adults in the cemetery, we may conclude that the settlement was abandoned after approx. one generation. Population heterogeneity is furthermore supported by the carbon and nitrogen isotope data. They indicate that a group of high-ranking men had access to larger shares of animal-derived food whilst a few individuals consumed remarkable amounts of millet. The inferred dynamics of the burial community are in agreement with hypotheses of a highly mobile lifestyle during the Migration Period and a short-term occupation of Pannonia by Lombard settlers as conveyed by written sources.     

Fractionation of the stable isotopes of inorganic carbon by seagrasses

The δ¹³C values for seagrasses collected along the Texas Gulf Coast range from −10.9 to −11.4‰. These values are similar to the δ¹³C values of terrestrial C₄ plants, but seagrasses lack bundle sheath cells which are important in determining the δ¹³C values of C₄ plants. This work attempts to explain the reason the δ¹³C values of seagrasses resemble the δ¹³C values of C₄ plants.     

Compensation point and isotopic characteristics of c(3)/c(4) intermediates and hybrids in panicum

Leaf CO₂ compensation points and stable hydrogen, oxygen and carbon isotope ratios were determined for Panicum species including C₃/C₄ intermediate photosynthesis plants, hybrids between C₃/C₄ intermediates and C₃ plants, C₃ and C₄ plants in the Panicum genus as well as several other C₃ and C₄ plants. C₃ plants had the highest compensation points, followed by hybrids, C₃/C₄ intermediates, and C₄ plants. δ¹³C values of cellulose nitrate and saponifiable lipids from C₄ plants were about 10‰ higher than those observed for cellulose nitrate and saponifiable lipids of C₃/C₄ intermediates, hybrids, and C₃ plants. Oxygen isotope ratios of cellulose as well as those of leaf water were similar for all plants. There was substantial variability in the δD values of cellulose nitrate among the plants studied. In contrast, such variability was not observed in δD values of water distilled from the leaves, nor in the δD values of the saponifiable lipids. Variability in δD values of cellulose nitrate from C₃/C₄ intermediates, hybrids, C₃, and C₄ plants is due to fractionations occurring during biochemical reactions specific to leaf carbohydrate metabolism.     

Seasonality and Paleoecology of the Late Cretaceous Multi-Taxa Vertebrate Assemblage of “Lo Hueco” (Central Eastern Spain)

Isotopic studies of multi-taxa terrestrial vertebrate assemblages allow determination of paleoclimatic and paleoecological aspects on account of the different information supplied by each taxon. The late Campanian-early Maastrichtian “Lo Hueco” Fossil-Lagerstätte (central eastern Spain), located at a subtropical paleolatitude of ~31°N, constitutes an ideal setting to carry out this task due to its abundant and diverse vertebrate assemblage. Local δ¹⁸O_PO4 values estimated from δ¹⁸O_PO4 values of theropods, sauropods, crocodyliforms, and turtles are close to δ¹⁸O_H2O values observed at modern subtropical latitudes. Theropod δ¹⁸O_H2O values are lower than those shown by crocodyliforms and turtles, indicating that terrestrial endothermic taxa record δ¹⁸O_H2O values throughout the year, whereas semiaquatic ectothermic taxa δ¹⁸O_H2O values represent local meteoric waters over a shorter time period when conditions are favorable for bioapatite synthesis (warm season). Temperatures calculated by combining theropod, crocodyliform, and turtle δ¹⁸O_H2O values and gar δ¹⁸O_PO4 have enabled us to estimate seasonal variability as the difference between mean annual temperature (MAT, yielded by theropods) and temperature of the warmest months (TWMs, provided by crocodyliforms and turtles). ΔTWMs-MAT value does not point to a significantly different seasonal thermal variability when compared to modern coastal subtropical meteorological stations and Late Cretaceous rudists from eastern Tethys. Bioapatite and bulk organic matter δ¹³C values point to a C₃ environment in the “Lo Hueco” area. The estimated fractionation between sauropod enamel and diet is ~15‰. While waiting for paleoecological information yielded by the ongoing morphological study of the “Lo Hueco” crocodyliforms, δ¹³C and δ¹⁸O_CO3 results point to incorporation of food items with brackish influence, but preferential ingestion of freshwater. “Lo Hueco” turtles showed the lowest δ¹³C and δ¹⁸O_CO3 values of the vertebrate assemblage, likely indicating a diet based on a mixture of aquatic and terrestrial C₃ vegetation and/or invertebrates and ingestion of freshwater.     

Using the Stable Carbon and Nitrogen Isotope Compositions of Vervet Monkeys (Chlorocebus pygerythrus) to Examine Questions in Ethnoprimatology

This study seeks to understand how humans impact the dietary patterns of eight free-ranging vervet monkey (Chlorocebus pygerythrus) groups in South Africa using stable isotope analysis. Vervets are omnivores that exploit a wide range of habitats including those that have been anthropogenically-disturbed. As humans encroach upon nonhuman primate landscapes, human-nonhuman primate interconnections become increasingly common, which has led to the rise of the field of ethnoprimatology. To date, many ethnoprimatological studies have examined human-nonhuman primate associations largely in qualitative terms. By using stable carbon (δ¹³C) and nitrogen (δ¹⁵N) isotope analysis, we use quantitative data to understand the degree to which humans impact vervet monkey dietary patterns. Based on initial behavioral observations we placed the eight groups into three categories of anthropogenic disturbance (low, mid, and high). Using δ¹³C and δ¹⁵N values we estimated the degree to which each group and each anthropogenically-disturbed category was consuming C₄ plants (primarily sugar cane, corn, or processed foods incorporating these crops). δ¹³C values were significantly different between groups and categories of anthropogenic-disturbance. δ¹⁵N values were significantly different at the group level. The two vervet groups with the highest consumption of C₄ plants inhabited small nature reserves, appeared to interact with humans only sporadically, and were initially placed in the mid level of anthropogenic-disturbance. However, further behavioral observations revealed that the high δ¹³C values exhibited by these groups were linked to previously unseen raiding of C₄ crops. By revealing these cryptic feeding patterns, this study illustrates the utility of stable isotopes analysis for some ethnoprimatological questions.     

Assessing Human Diet and Movement in the Tongan Maritime Chiefdom Using Isotopic Analyses

The rise of stratified societies fundamentally influences the interactions between status, movement, and food. Using isotopic analyses, we assess differences in diet and mobility of individuals excavated from two burial mounds located at the `Atele burial site on Tongatapu, the main island of the Kingdom of Tonga (c. 500 - 150 BP). The first burial mound (To-At-1) was classified by some archaeologists as a commoner’s mound while the second burial mound (To-At-2) was possibly used for interment of the chiefly class. In this study, stable isotope analyses of diet (δ¹³C, δ¹⁵N, and δ³⁴S; n = 41) are used to asses paleodiet and ⁸⁷Sr/⁸⁶Sr ratios (n = 30) are analyzed to investigate individual mobility to test whether sex and social status affected these aspects of life. Our results show significant differences in diet between burial mounds and sexes. Those interred in To-At-2 displayed lower δ¹³C values, indicating they ate relatively more terrestrial plants (likely starchy vegetable staples) compared with To-At-1 individuals. Females displayed significantly lower δ¹⁵N values compared with males within the entire assemblage. No differences in δ³⁴S values were observed between sexes or burial mound but it is possible that sea spray or volcanism may have affected these values. One individual displayed the strontium isotopic composition representative of a nonlocal immigrant (outside 2SD of the mean). This suggests the hegemonic control over interisland travel, may have prevented long-term access to the island by non-Tongans exemplifying the political and spiritual importance of the island of Tongatapu in the maritime chiefdom.     

Stable isotope canopy effects for sympatric monkeys at Ta? Forest,C?te d'Ivoire

This study tests the hypothesis that vertical habitat preferences of different monkey species inhabiting closed canopy rainforest are reflected in oxygen isotopes. We sampled bone from seven sympatric cercopithecid species in the Taï forest, Côte d''Ivoire, where long-term study has established taxon-specific patterns of habitat use and diet. Modern rib samples (n = 34) were examined for oxygen (δ¹⁸O_ap) and carbon (δ¹³C_ap) from bone apatite (‘bioapatite’), and carbon (δ¹³C_co) and nitrogen (δ¹⁵N_co) from bone collagen. Results are consistent for C₃ feeders in a closed canopy habitat. Low irradiance and evapotranspiration, coupled with high relative humidity and recycled CO₂ in forest understory, contribute to observed isotopic variability. Both δ¹³C_co and δ¹³C_ap results reflect diet; however, δ¹³C values are not correlated with species preference for canopy height. By contrast, δ¹⁸O_ap results are correlated with mean observed height and show significant vertical partitioning between taxa feeding at ground, lower and upper canopy levels. This oxygen isotope canopy effect has important palaeobiological implications for reconstructing vertical partitioning among sympatric primates and other species in tropical forests.     

Carbon Isotope Composition of Nighttime Leaf-Respired CO2 in the Agricultural-Pastoral Zone of the Songnen Plain,Northeast China

Variations in the carbon isotope signature of leaf dark-respired CO₂ (δ¹³C_R) within a single night is a widely observed phenomenon. However, it is unclear whether there are plant functional type differences with regard to the amplitude of the nighttime variation in δ¹³C_R. These differences, if present, would be important for interpreting the short-term variations in the stable carbon signature of ecosystem respiration and the partitioning of carbon fluxes. To assess the plant functional type differences relating to the magnitude of the nighttime variation in δ¹³C_R and the respiratory apparent fractionation, we measured the δ¹³C_R, the leaf gas exchange, and the δ¹³C of the respiratory substrates of 22 species present in the agricultural-pastoral zone of the Songnen Plain, northeast China. The species studied were grouped into C₃ and C₄ plants, trees, grasses, and herbs. A significant nocturnal shift in δ¹³C_R was detected in 20 of the studied species, with the magnitude of the shift ranging from 1‰ to 5.8‰. The magnitude of the nighttime variation in δ¹³C_R was strongly correlated with the daytime cumulative carbon assimilation, which suggests that variation in δ¹³C_R were influenced, to some extent, by changes in the contribution of malate decarboxylation to total respiratory CO₂ flux. There were no differences in the magnitude of the nighttime variation in δ¹³C_R between the C₃ and C₄ plants, as well as among the woody plants, herbs and graminoids. Leaf respired CO₂ was enriched in ¹³C compared to biomass, soluble carbohydrates and lipids; however the magnitude of enrichment differed between 8 pm and 4 am, which were mainly caused by the changes in δ¹³C_R. We also detected the plant functional type differences in respiratory apparent fractionation relative to biomass at 4 am, which suggests that caution should be exercised when using the δ¹³C of bulk leaf material as a proxy for the δ¹³C of leaf-respired CO₂.     

Stable Carbon Isotope Ratios of Lipid Biomarkers of Sulfate-Reducing Bacteria

We examined the potential use of natural-abundance stable carbon isotope ratios of lipids for determining substrate usage by sulfate-reducing bacteria (SRB). Four SRB were grown under autotrophic, mixotrophic, or heterotrophic growth conditions, and the δ¹³C values of their individual fatty acids (FA) were determined. The FA were usually ¹³C depleted in relation to biomass, with Δδ¹³C_{(FA − biomass)} of −4 to −17‰; the greatest depletion occurred during heterotrophic growth. The exception was Desulfotomaculum acetoxidans, for which substrate limitation resulted in biomass and FA becoming isotopically heavier than the acetate substrate. The δ¹³C values of FA in Desulfotomaculum acetoxidans varied with the position of the double bond in the monounsaturated C₁₆ and C₁₈ FA, with FA becoming progressively more ¹³C depleted as the double bond approached the methyl end. Mixotrophic growth of Desulfovibrio desulfuricans resulted in little depletion of the i17:1 biomarker relative to biomass or acetate, whereas growth with lactate resulted in a higher proportion of i17:1 with a greater depletion in ¹³C. The relative abundances of 10Me16:0 in Desulfobacter hydrogenophilus and Desulfobacterium autotrophicum were not affected by growth conditions, yet the Δδ¹³C_{(FA − substrate)} values of 10Me16:0 were considerably greater during autotrophic growth. These experiments indicate that FA δ¹³C values can be useful for interpreting carbon utilization by SRB in natural environments.     

Desert Tortoise (Gopherus agassizii) Dietary Specialization Decreases across a Precipitation Gradient

We studied the plant resource use between and within populations of desert tortoise (Gopherus agassizii) across a precipitation gradient in the Sonoran Desert of Arizona. The carbon and nitrogen stable isotope values in animal tissues are a reflection of the carbon and nitrogen isotope values in diet, and consequently represent a powerful tool to study animal feeding ecology. We measured the δ¹³C and δ¹⁵N values in the growth rings on the shells of tortoises in different populations to characterize dietary specialization and track tortoise use of isotopically distinct C₄/CAM versus C₃ plant resources. Plants using C₃ photosynthesis are generally more nutritious than C₄ plants and these trait differences can have important growth and fitness consequences for consumers. We found that dietary specialization decreases in successively drier and less vegetated sites, and that broader population niche widths are accompanied by an increase in the dietary variability between individuals. Our results highlight how individual consumer plant resource use is bounded under a varying regime of precipitation and plant productivity, lending insight into how intra-individual dietary specialization varies over a spatial scale of environmental variability.     

Physiological and isotopic aspects of photosynthesis in peperomia

Physiological and isotopic aspects of several Peperomia species were investigated. All but one species had C₃-like stomatal behavior, in that stomata were open during the day and closed during the night. In these species, most atmospheric CO₂ uptake occurred during the day. Concurrent with this stomatal behavior, there were Crassulacean acid metabolism-like acid fluctuations in most species. Carbon and hydrogen isotope ratios of cellulose nitrate from Peperomia reflect their physiological behavior. The δ¹³C values of cellulose nitrate from Peperomia species were similar to values observed in C₃ plants and consistent with the daytime uptake of exogeneous CO₂ via the C₃ photosynthetic pathway. The δD values of cellulose nitrate from Peperomia species approach those of Crassulacean acid metabolism plants. These elevated δD values are caused by fractionations occurring during biochemical reactions and not as a consequence of water relations.     

Resource partitioning among top predators in a Miocene food web

The exceptional fossil sites of Cerro de los Batallones (Madrid Basin, Spain) contain abundant remains of Late Miocene mammals. From these fossil assemblages, we have inferred diet, resource partitioning and habitat of three sympatric carnivorous mammals based on stable isotopes. The carnivorans include three apex predators: two sabre-toothed cats (Felidae) and a bear dog (Amphicyonidae). Herbivore and carnivore carbon isotope (δ¹³C) values from tooth enamel imply the presence of a woodland ecosystem dominated by C₃ plants. δ¹³C values and mixing-model analyses suggest that the two sabre-toothed cats, one the size of a leopard and the other the size of a tiger, consumed herbivores with similar δ¹³C values from a more wooded portion of the ecosystem. The two sabre-toothed cats probably hunted prey of different body sizes, and the smaller species could have used tree cover to avoid encounters with the larger felid. For the bear dog, δ¹³C values are higher and differ significantly from those of the sabre-toothed cats, suggesting a diet that includes prey from more open woodland. Coexistence of the sabre-toothed cats and the bear dog was likely facilitated by prey capture in different portions of the habitat. This study demonstrates the utility of stable isotope analysis for investigating the behaviour and ecology of members of past carnivoran guilds.     

Autotrophy in maize husk leaves : evaluation using natural abundance of stable isotopes

The natural abundance of carbon and hydrogen isotopic composition, expressed as a δ¹³C value of plant dry matter and cellulose in the hypsophylls (husk leaves) of maize (Zea mays L.) was measured and compared with that of leaves and cobs. The δ¹³C values of outer hypsophylls were usually 2 to 3%‰ more negative than leaves or other tissues, and became more negative with increasing chlorophyll content, indicating significant local C₃ pathway fixation of CO₂ in the outer hypsophylls. The δD values indicated a significant part of hypsophyll cellulose was derived from heterotrophic sources (sucrose from C₄ photosynthesis in other tissues). Isotopic mass balance calculations allowed quantitative estimation of these carbon sources and, in the samples examined, about 16% of hypsophyll cellulose was derived from local C₃ photosynthesis, about 62% from local C₄ photosynthesis, and about 22% from sucrose imported from other leaves.     

Photosynthetic carbon metabolism of a marine grass

The δ¹³C value of a tropical marine grass Thalassia testudinum is −9.04‰. This value is similar to the δ¹³C value of terrestrial tropical grasses. The δ¹³C values of the organic acid fraction, the amino acid fraction, the sugar fraction, malic acid, and glucose are: −11.2‰, −13.1‰, −10.1‰, −11.1‰, and −11.5‰, respectively. The δ¹³C values of malic acid and glucose of Thalassia are similar to the δ¹³C values of these intermediates in sorghum leaves and attest to the presence of the photosynthetic C₄-dicarboxylic acid pathway in this marine grass. The inorganic HCO₃⁻ for the growth of the grass fluctuates between −6.7 to −2.7‰ during the day. If CO₂ fixation in Thalassia is catalyzed by phosphoenolpyruvate carboxylase (which would result in a −3‰ fractionation between HCO₃⁻ and malic acid), the predicted δ¹³C value for Thalassia would be −9.7 to −5.7‰. This range is close to the observed range of −12.6 to −7.8‰ for Thalassia and agree with the operation of the C₄-dicarboxylic acid pathway in this plant. The early products of the fixation of HCO₃⁻ in the leaf sections are malic acid and aspartic acid which are similar to the early products of CO₂ fixation in C₄ terrestrial plants.     

The Influence of Growth Rate on 2H/1H Fractionation in Continuous Cultures of the Coccolithophorid Emiliania huxleyi and the Diatom Thalassiosira pseudonana

The hydrogen isotope (²H/¹H) ratio of lipids from phytoplankton is a powerful new tool for reconstructing hydroclimate variations in the geologic past from marine and lacustrine sediments. Water ²H/¹H changes are reflected in lipid ²H/¹H changes with R² > 0.99, and salinity variations have been shown to cause about a 1‰ change in lipid δ²H values per unit (ppt) change in salinity. Less understood are the effects of growth rate, nutrient limitation and light on ²H/¹H fractionation in phytoplankton. Here we present the first published study of growth rate effects on ²H/¹H fractionation in the lipids of coccolithophorids grown in continuous cultures. Emiliania huxleyi was cultivated in steady state at four growth rates and the δ²H value of individual alkenones (C_37:2, C_37:3, C_38:2, C_38:3), fatty acids (C_14:0, C_16:0, C_18:0), and 24-methyl cholest-5,22-dien-3β-ol (brassicasterol) were measured. ²H/¹H fractionation increased in all lipids as growth rate increased by 24‰ to 79‰ (div d^-1)^-1. We attribute this response to a proportional increase in the fraction of NADPH from Photosystem I (PS1) of photosynthesis relative to NADPH from the cytosolic oxidative pentose phosphate (OPP) pathway in the synthesis of lipids as growth rate increases. A 3-endmember model is presented in which lipid hydrogen comes from NADPH produced in PS1, NADPH produced by OPP, and intracellular water. With published values or best estimates of the fractionation factors for these sources (α_PS1 = 0.4, α_OPP = 0.75, and α_H2O = 0) and half of the hydrogen in a lipid derived from water the model indicates α_lipid = 0.79. This value is within the range measured for alkenones (α_alkenone = 0.77 to 0.81) and fatty acids (α_FA = 0.75 to 0.82) in the chemostat cultures, but is greater than the range for brassicasterol (α_{brassicasterol} = 0.68 to 0.72). The latter is attributed to a greater proportion of hydrogen from NADPH relative to water in isoprenoid lipids. The model successfully explains the increase in ²H/¹H fractionation in the sterol 24-methyl-cholesta-5,24(28)-dien-3β-ol from marine centric diatom T. pseudonana chemostat cultures as growth rate increases. Insensitivity of α_FA in those same cultures may be attributable to a larger fraction of hydrogen in fatty acids sourced from intracellular water at the expense of NADPH as growth rate increases. The high sensitivity of α to growth rate in E. huxleyi lipids and a T. pseudonana sterol implies that any change in growth rate larger than ~0.15 div d^-1 can cause a change in δ²H_lipid that is larger than the analytical error of the measurement (~5‰), and needs to be considered when interpreting δ²H_lipid variations in sediments.     

Quantifying Inter-Laboratory Variability in Stable Isotope Analysis of Ancient Skeletal Remains

Over the past forty years, stable isotope analysis of bone (and tooth) collagen and hydroxyapatite has become a mainstay of archaeological and paleoanthropological reconstructions of paleodiet and paleoenvironment. Despite this method''s frequent use across anthropological subdisciplines (and beyond), the present work represents the first attempt at gauging the effects of inter-laboratory variability engendered by differences in a) sample preparation, and b) analysis (instrumentation, working standards, and data calibration). Replicate analyses of a ¹⁴C-dated ancient human bone by twenty-one archaeological and paleoecological stable isotope laboratories revealed significant inter-laboratory isotopic variation for both collagen and carbonate. For bone collagen, we found a sizeable range of 1.8‰ for δ¹³C_col and 1.9‰ for δ¹⁵N_col among laboratories, but an interpretatively insignificant average pairwise difference of 0.2‰ and 0.4‰ for δ¹³C_col and δ¹⁵N_col respectively. For bone hydroxyapatite the observed range increased to a troublingly large 3.5‰ for δ¹³C_ap and 6.7‰ for δ¹⁸O_ap, with average pairwise differences of 0.6‰ for δ¹³C_ap and a disquieting 2.0‰ for δ¹⁸O_ap. In order to assess the effects of preparation versus analysis on isotopic variability among laboratories, a subset of the samples prepared by the participating laboratories were analyzed a second time on the same instrument. Based on this duplicate analysis, it was determined that roughly half of the isotopic variability among laboratories could be attributed to differences in sample preparation, with the other half resulting from differences in analysis (instrumentation, working standards, and data calibration). These findings have serious implications for choices made in the preparation and extraction of target biomolecules, the comparison of results obtained from different laboratories, and the interpretation of small differences in bone collagen and hydroxyapatite isotope values. To address the issues arising from inter-laboratory comparisons, we devise a novel measure we term the Minimum Meaningful Difference (MMD), and demonstrate its application.     

Stable Water Use Efficiency of Tibetan Alpine Meadows in Past Half Century: Evidence from Wool δ13C Values

Understanding the influences of climatic changes on water use efficiency (WUE) of Tibetan alpine meadows is important for predicting their long-term net primary productivity (NPP) because they are considered very sensitive to climate change. Here, we collected wool materials produced from 1962 to 2010 and investigated the long-term WUE of an alpine meadow in Tibet on basis of the carbon isotope values of vegetation (δ ¹³C_veg). The values of δ ¹³C_veg decreased by 1.34‰ during 1962–2010, similar to changes in δ ¹³C values of atmospheric CO₂. Carbon isotope discrimination was highly variable and no trend was apparent in the past half century. Intrinsic water use efficiency (W _i) increased by 18 μmol·mol^–1 (approximately 23.5%) during 1962–2010 because the increase in the intercellular CO₂ concentration (46 μmol·mol^–1) was less than that in the atmospheric CO₂ concentration (C _a, 73 μmol·mol^–1). In addition, W _i increased significantly with increasing growing season temperature and C _a. However, effective water use efficiency (W _e) remained relatively stable, because of increasing vapor pressure deficit. C _a, precipitation, and growing season temperature collectively explained 45% of the variation of W _e. Our findings indicate that the W _e of alpine meadows in the Tibetan Plateau remained relatively stable by physiological adjustment to elevated C _a and growing season temperature. These findings improve our understanding and the capacity to predict NPP of these ecosystems under global change scenarios.     

Ethylene Removal at Low Temperatures under Biofilter and Batch Conditions

Removal of the plant hormone ethylene (C₂H₄) is often required by horticultural storage facilities, which are operated at temperatures below 10°C. The aim of this study was to demonstrate an efficient, biological C₂H₄ removal under such low-temperature conditions. Peat-soil, acclimated to degradation of C₂H₄, was packed in a biofilter (687 cm³) and subjected to an airflow (~73 ml min⁻¹) with 2 ppm (μl liter⁻¹) C₂H₄. The C₂H₄ removal efficiencies achieved at 20, 10, and 5°C, respectively, were 99.0, 98.8, and 98.4%. This corresponded to C₂H₄ levels of 0.022 to 0.032 ppm in the biofilter outlet air. At 2°C, the average C₂H₄ removal efficiency dropped to 83%. The detailed temperature response of C₂H₄ removal was tested under batch conditions by incubation of 1-g soil samples in a temperature gradient ranging from 0 to 29°C with increments of 1°C. The C₂H₄ removal rate was highest at 26°C (0.85 μg of C₂H₄ g [dry weight]⁻¹ h⁻¹), but remained at levels of 0.14 to 0.28 μg of C₂H₄ g (dry weight)⁻¹ h⁻¹ at 0 to 10°C. At 35 to 40°C, the C₂H₄ removal rate was negligible (0.02 to 0.06 μg of C₂H₄ g [dry weight]⁻¹ h⁻¹). The Q₁₀ (i.e., the ratio of rates 10°C apart) for C₂H₄ removal was 1.9 for the interval 0 to 10°C. In conclusion, the present results demonstrated microbial C₂H₄ removal, which proceeded at 0 to 2°C and produced a moderately psychrophilic temperature response.     

Ratios of Carbon Isotopes in Microbial Lipids as an Indicator of Substrate Usage

The occurrence and abundance of microbial fatty acids have been used for the identification of microorganisms in microbial communities. However, these fatty acids can also be used as indicators of substrate usage. For this, a systematic investigation of the discrimination of the stable carbon isotopes by different microorganisms is necessary. We grew 11 strains representing major bacterial and fungal species with four different isotopically defined carbon sources and determined the isotope ratios of fatty acids of different lipid fractions. A comparison of the differences of δ¹³C values of palmitic acid (C_16:0) with the δ¹³C values of the substrates revealed that the isotope ratio is independent of the growth stage and that most microorganisms showed enrichment of C_16:0 with ¹³C when growing on glycerol. With the exception of Burkholderia gladioli, all microorganism showed depletion of ¹³C in C_16:0 while incorporating the carbons of glucose, and most of them were enriched with ¹³C from mannose, with the exception of Pseudomonas fluorescens and the Zygomycotina. Usually, the glycolipid fractions are depleted in ¹³C compared to the phospholipid fractions. The δ¹³C pattern was not uniform within the different fatty acids of a given microbial species. Generally, tetradecanoic acid (C_14:0) was depleted of ¹³C compared to palmitic acid (C_16:0) while octadecanoic acid (C_18:0) was enriched. These results are important for the calibration of a new method in which δ¹³C values of fatty acids from the environment delineate the use of bacterial substrates in an ecosystem.     

Pastoralism in Northern Peru during Pre-Hispanic Times: Insights from the Mochica Period (100–800 AD) Based on Stable Isotopic Analysis of Domestic Camelids

Llama (Lama glama) and alpaca (Vicugna pacos) are the only large domesticated animals indigenous to the Americas. Pastoralism occupies a fundamental economic, social and religious role in Andean life. Today, camelid livestock are confined to the ecozone of the puna (above 3,500 masl), while their presence on the Pacific coast during pre-Hispanic times is attested by archaeological skeletal remains. This study aims to document herding practices on the northern Peruvian coast during the Early Intermediate Period (200 BC-600 AD) by gaining insights into diet, location of breeding and mobility of archaeological camelids from the funerary and ritual contexts of two Mochica sites, Uhle Platform in Huacas de Moche and El Brujo. The three first early years and the long-term life histories of the animals were documented by the combined bulk analysis of bone collagen (δ¹³C_col and δ¹⁵N_col) and bone structural carbonate (δ¹³C_bone and δ¹⁸O_bone) and the serial analysis of structural carbonate of molar tooth enamel (δ¹³C_enamel and δ¹⁸O_enamel). Mochica camelids were bred in the low and/or middle valleys, unlike their modern counterparts, who are restricted to highland puna C₃ pastures. Archaeological camelids had diverse and complex life histories, usually with substantial maize foddering. An ontogenetic switch in diet and possible residential mobility during the course of life were identified for some specimens. Although the inference of geographic origin from δ¹⁸O_bone and δ¹⁸O_enamel values was limited because of the lack of understanding of the influence of environmental and biological factors, tooth enamel analysis has great potential for exploring camelid herding practices and Andean pastoralism. Our study suggested that Mochica herders adapted their practices to the difficult lowland environment and that herding practices were varied and not restricted to breeding at higher altitudes. The role of maize in different aspects of the economic life of the Mochicas is also underlined.