δ18O‐derived incubation temperatures of oviraptorosaur eggs

In order to determine the incubation temperature of eggs laid by non‐avian dinosaurs, we analysed the oxygen isotope compositions of both eggshell carbonate (δ¹⁸O_c) and embryo bone phosphate (δ¹⁸O_p) from seven oviraptorosaur eggs with preserved in ovo embryo bones. These eggs come from the Upper Cretaceous Nanxiong Formation of Jiangxi Province, China. Oviraptorosaur theropods were selected because of their known brooding behaviour as evidenced by preserved adult specimens fossilized in brooding posture on their clutch. Incubation temperature of these embryos was estimated based on the following considerations: eggshell δ¹⁸O_c value reflects the oxygen isotope composition of egg water fluid; embryo bones precipitate from the same egg fluid; and oxygen isotope fractionation between phosphate and water is controlled by the egg temperature. A time‐dependent model predicting the δ¹⁸O_p evolution of the embryo skeleton during incubation as a function of egg temperature was built, and measured δ¹⁸O_c and δ¹⁸O_p values used as boundary conditions. According to the model outputs, oviraptorosaurs incubated their eggs within a 35–40°C range, similar to extant birds and compatible with the known active brooding behaviour of these theropod dinosaurs. Provided that both eggshell and embryo bones preserved their original oxygen isotope compositions, this method could be extended to investigate some reproductive traits of other extinct groups of oviparous amniotes.     

Cribra orbitalia as a potential indicator of childhood stress: Evidence from paleopathology,stable C,N, and O isotopes,and trace element concentrations in children from a 17th⿿18th century cemetery in JĿkabpils,Latvia

Cribra orbitalia (CO), or porotic hyperostosis (PH) of the orbital roof, is one of the most common pathological conditions found in archaeological subadult skeletal remains. Reaching frequencies higher than 50% in many prehistoric samples, CO has been generally attributed to a variety of factors including malnutrition (e.g., megaloblastic anemia) and parasitism. In this study, we tested the relationship between CO, trace element concentrations, and stable isotope values (δ¹³C, δ¹⁵N, δ¹⁸O) in subadult skeletons from a 17^th to 18^th century cemetery in the historic town of JĿkabpils, Latvia. A total of 28 subadults were examined, seven of which (25%) showed evidence of CO. Bioarchaeological evidence indicated high mortality for children in this cemetery: half of the burials were subadults under the age of 14, while a third were under the age of four. Life expectancy at birth was estimated to have been only 21.6 years. Trace element concentrations measured by Inductively Coupled Plasma ⿿ Mass Spectrometry (ICP-MS) showed no relationship between presence or absence of CO and levels of manganese, zinc, strontium, barium, copper, cadmium, or lead in the bones (p > 0.05). However, a significant correlation (p < 0.05) was found between the presence of CO and decreased levels of iron. The correlations between CO and decreased levels of copper and lead approached significance (p = 0.056 for both elements). Individuals with CO furthermore displayed significantly lower δ¹⁵N isotope values, suggesting greater consumption of lower trophic level food resources than those unaffected by CO; δ¹³C and δ¹⁸O values, in contrast, showed no significant differences. These results suggest that the prevalence of CO may be related to dietary deficiencies. In this case, low iron levels may also signify a diet low in other key vitamins (e.g., B₉ and B₁₂), which are known to cause megaloblastic anemia.     

Oxygen isotope fractionations across individual leaf carbohydrates in grass and tree species

Almost no δ¹⁸O data are available for leaf carbohydrates, leaving a gap in the understanding of the δ¹⁸O relationship between leaf water and cellulose. We measured δ¹⁸O values of bulk leaf water (δ¹⁸O_LW) and individual leaf carbohydrates (e.g. fructose, glucose and sucrose) in grass and tree species and δ¹⁸O of leaf cellulose in grasses. The grasses were grown under two relative humidity (rH) conditions. Sucrose was generally ¹⁸O‐enriched compared with hexoses across all species with an apparent biosynthetic fractionation factor (ε_bio) of more than 27‰ relative to δ¹⁸O_LW, which might be explained by isotopic leaf water and sucrose synthesis gradients. δ¹⁸O_LW and δ¹⁸O values of carbohydrates and cellulose in grasses were strongly related, indicating that the leaf water signal in carbohydrates was transferred to cellulose (ε_bio = 25.1‰). Interestingly, damping factor p_exp_x, which reflects oxygen isotope exchange with less enriched water during cellulose synthesis, responded to rH conditions if modelled from δ¹⁸O_LW but not if modelled directly from δ¹⁸O of individual carbohydrates. We conclude that δ¹⁸O_LW is not always a good substitute for δ¹⁸O of synthesis water due to isotopic leaf water gradients. Thus, compound‐specific δ¹⁸O analyses of individual carbohydrates are helpful to better constrain (post‐)photosynthetic isotope fractionation processes in plants.     

Ontogenetic effects on stable carbon and oxygen isotopes in tests of live (Rose Bengal stained) benthic foraminifera from the Pakistan continental margin

We determined the stable oxygen and carbon isotopic composition of live (Rose Bengal stained) tests belonging to different size classes of two benthic foraminiferal species from the Pakistan continental margin. Samples were taken at two sites, with water depths of about 135 and 275 m, corresponding to the upper boundary and upper part of the core region of the oxygen minimum zone (OMZ). For Uvigerina ex gr. Uvigerina semiornata and Bolivina aff. Bolivina dilatata, δ¹³C and δ¹⁸O values increased significantly with increasing test size. In the case of Uvigerina ex gr. U. semiornata, δ¹³C increased linearly by about 0.105‰ for each 100-μm increment in test size, whereas δ¹⁸O increased by 0.02 to 0.06‰ per 100 μm increment. For Bolivina aff. B. dilatata the relationship between test size and stable isotopic composition is better described by logarithmic equations. A strong positive linear correlation is observed between δ¹⁸O and δ¹³C values of both taxa, with a constant ratio of δ¹⁸O and δ¹³C values close to 2:1. This suggests that the strong ontogenetic effect is mainly caused by kinetic isotope fractionation during CO₂ uptake. Our data underline the necessity to base longer δ¹⁸O and δ¹³C isotope records derived from benthic foraminifera on size windows of 100 μm or less. This is already common practice in down-core isotopic studies of planktonic foraminifera.     

Tracing prey origins,proportions and feeding periods for predatory beetles from agricultural systems using carbon and nitrogen stable isotope analyses

Predatory beetles are an important component of the natural enemy complex that preys on insect pests such as aphids within agroecosystems. Tracing diet origins and movement of natural enemies aids understanding their role in the food web and informs strategies for their effective conservation. Field sampling and laboratory experiments were carried out to examine the changes of carbon and nitrogen stable isotope ratios (δ¹³C and δ¹⁵N) among crops (cotton and maize), pests (cotton and maize aphids), and between wing and abdomen of predatory beetles, Propylea japonica, and to test the hypothesis that prey origins, proportions and feeding periods of the predatory beetles can be deduced by this stable isotope analysis. Results showed that the δ¹³C values both in wing and abdomen of adult P. japonica were changing from a C₃- to a C₄-based diet of aphids reared on maize or cotton, respectively; the isotope ratio of their new C₄ substrates were detectable within 7 days and the δ¹⁵N values began to reflect their new C₄ substrates within 3 days. The relationship between δ¹³C and δ¹⁵N values of P. japonica adults in wing or abdomen and diets of aphids from a C₃-based resource transitioning to a C₄-based resource were described best in linear or quadratic equations. Results suggest that integrative analysis of δ¹³C and δ¹⁵N values can be regarded as a useful method for quantifying to trace prey origins, proportions of diets and feeding periods of natural enemies. The results can provide quantifying techniques for habitat management of natural enemies.     

Soil and tree ring chemistry of Pinus banksiana and Populus tremuloides stands as indicators of changes in atmospheric environments in the oil sands region of Alberta,Canada

The impact of chronic air pollution such as increased CO₂ and NO_x emissions on forest ecosystems in the Athabasca oil sands region in Alberta, Canada, was investigated in Pinus banksiana (jack pine) and Populus tremuloides (trembling aspen, aspen) stands in two watersheds (NE7 and SM8) located at different distances from the main emission sources of oil sands mining and upgrading facilities, using δ¹³C, δ¹⁵N, and Ca/Al of soil and tree ring samples as indicators. Watershed NE7 was exposed to greater amounts of acid deposition due to its closeness to the mining and upgrading area. The δ¹⁵N in the forest floor was lower (p < 0.05) in NE7 (ranged from −1.42 to −0.87‰) than in SM8 (−0.54 to 1.43‰), implying a greater amount of recent deposition of ¹⁵N-depleted N in NE7. Tree ring δ¹³C gradually decreased over time for both tree species/watersheds, indicating the influence of ¹³C-depleted CO₂ emitted from industrial sources. Tree ring N concentration and δ¹⁵N were not different between watersheds and did not significantly change with time. Interestingly, however, the difference between watersheds (NE7–SM8) that is expressed as Diff_N (for N) increased with concomitant decreases in Diff_δ¹⁵N over time, implying greater increases in ¹⁵N-depleted N input in NE7 than in SM8. Such trends were stronger in aspen stands (R² = 0.64 and p < 0.001 for Diff_N and R² = 0.44 and p < 0.01 for Diff_δ¹⁵N between 1964 and 2009) than in jack pine stands. We conclude that δ¹⁵N in the forest floor and differences in N and δ¹⁵N of tree rings between watersheds are useful indicators reflecting the impact of spatial variations of air pollution on forest stands in the Athabasca oil sands region in western Canada.     

Tarbellastraea (Scleractinia): A new stable isotope archive for Late Miocene paleoenvironments in the Mediterranean

Geochemical proxy records of sea surface temperature (SST) or sea surface salinity (SSS) variability on intra- and interannual time-scales in corals from geological periods older than Pleistocene are extremely rare due to pervasive diagenetic alteration of coralline aragonite. Very recently, however, stable isotope data (δ¹⁸O, δ¹³C) from specimens of Porites of Late Miocene age (10 Ma) have been shown to preserve original environmental signatures. In this paper we describe new finds of the zooxanthellate corals Porites and Tarbellastraea in exceptional aragonite preservation from the island of Crete in sediments of Tortonian (～ 9 Ma) and Early Messinian (～ 7 Ma) age. Systematic, comparative stable isotope analysis of massive Tarbellastraea and Porites sampled from the same beds and localities reveal identical stable isotope fractionation patterns in both genera. Therefore, extinct Tarbellastraea represents an additional environmental archive fully compatible and mutually exchangeable with Porites. Provided that seasonal variations in δ¹⁸O reflect SST changes only, seasonal SST contrasts of 7.3 °C for the Tortonian and 4.8 °C for the Early Messinian are inferred, implying warmer summer and cooler winter SSTs during the Tortonian than during the Messinian. However, reduced δ¹⁸O seasonality (1.1‰ in the Tortonian and 0.7‰ in the Messinian) and slightly less negative mean δ¹⁸O in Messinian corals (? 2.4‰) compared to Tortonian specimens (? 2.7‰) may not necessarily indicate a long-term fall in SSTs, but changes in surface water δ¹⁸O, i.e. global ice build-up or enhanced evaporation during summer or increased precipitation/river discharge during winter and changes in insolation. On the other hand, coral communities of Tortonian and Messinian age in central Crete are identical, and compatible annual extension rates indicate similar average SSTs during the two investigated time periods. In addition, lithological and paleobotanical data from Central Crete document a change from humid to dry climatic conditions during the Late Miocene. Therefore, a likely explanation for the observed shift in coral mean δ¹⁸O and reduced δ¹⁸O seasonality from the Tortonian to the Early Messinian is a change in ambient seawater δ¹⁸O caused by a change in the hydrological balance towards high evaporation/high salinity during summer.     

Mg/Ca and δ18O in the brackish shallow-water benthic foraminifer Ammonia ‘beccarii’

Specimens of the benthic foraminifer Ammonia beccarii were cultured in the laboratory in order to determine the relation between temperature and Mg/Ca and oxygen isotope values in their tests. Asexual reproduction in this species provides a large number of juveniles that were allowed to grow into maturity at temperatures ranging from 10 to 27 °C and at salinities ranging from 18 to 33 PSU. The Mg/Ca in a calcite increase exponentially and δ¹⁸O decreases linearly with the temperature. Salinity has no significant impact on either Mg/Ca or δ¹⁸O. We show how the combination of these two parameters can be used to reconstruct seawater δ¹⁸O and temperature in shallow marine habitats.     

Interpreting species‐specific variation in tree‐ring oxygen isotope ratios among three temperate forest trees

Although considerable variation has been documented in tree‐ring cellulose oxygen isotope ratios (δ¹⁸O_cell) among co‐occurring species, the underlying causes are unknown. Here, we used a combination of field measurements and modelling to investigate the mechanisms behind variations in late‐wood δ¹⁸O_cell (δ¹⁸O_lc) among three co‐occurring species (chestnut oak, black oak and pitch pine) in a temperate forest. For two growing seasons, we quantified among‐species variation in δ¹⁸O_lc, as well as several variables that could potentially cause the δ¹⁸O_lc variation. Data analysis based on the δ¹⁸O_cell model rules out leaf water enrichment (Δ¹⁸O_lw) and tree‐ring formation period (Δt), but highlights source water δ¹⁸O (δ¹⁸O_sw) as an important driver for the measured difference in δ¹⁸O_lc between black and chestnut oak. However, the enriched δ¹⁸O_lc in pitch pine relative to the oaks could not be sufficiently explained by consideration of the above three variables only, but rather, we show that differences in the proportion of oxygen exchange during cellulose synthesis (p_ex) is most likely a key mechanism. Our demonstration of the relevance of some species‐specific features (or lack thereof) to δ¹⁸O_cell has important implications for isotope based ecophysiological/paleoclimate studies.     

The influence of seawater carbonate ion concentration [CO32−] on the stable carbon isotope composition of the planktic foraminifera species Globorotalia inflata

We sampled the upper water column for living planktic foraminifera along the SW-African continental margin. The species Globorotalia inflata strongly dominates the foraminiferal assemblages with an overall relative abundance of 70–90%. The shell δ¹⁸O and δ¹³C values of G. inflata were measured and compared to the predicted oxygen isotope equilibrium values (δ¹⁸O_eq) and to the carbon isotope composition of the total dissolved inorganic carbon (δ¹³C_DIC) of seawater. The δ¹⁸O of G. inflata reflects the general gradient observed in the predicted δ¹⁸O_eq profile, while the δ¹³C of G. inflata shows almost no variation with depth and the reflection of the δ¹³C_DIC in the foraminiferal shell seems to be covered by other effects. We found that offsets between δ¹⁸O_shell and predicted δ¹⁸O_eq in the surface mixed layer do not correlate to changes in seawater [CO₃²⁻].To calculate an isotopic mass balance of depth integrated growth, we used the oxygen isotope composition of G. inflata to estimate the fraction of the total shell mass that is grown within each plankton tow depth interval of the upper 500 m of the water column. This approach allows us to calculate the Δδ¹³C_{interval added-DIC}; i.e. the isotopic composition of calcite that was grown within a given depth interval. Our results consistently show that the Δδ¹³C_IA-DIC correlates negatively with in situ measured [CO₃²⁻] of the ambient water. Using this approach, we found Δδ¹³C_IA-DIC/[CO₃²⁻] slopes for G. inflata in the large size fraction (250–355 μm) of − 0.013‰ to 0.015‰ (μmol kg^− 1)^− 1 and of − 0.013‰ to 0.017‰ (μmol kg^− 1)^− 1 for the smaller specimens (150–250 μm). These slopes are in the range of those found for other non-symbiotic species, such as Globigerina bulloides, from laboratory culture experiments. Since the Δδ¹³C_IA-DIC/[CO₃²⁻] slopes from our field data are nearly identical to the slopes established from laboratory culture experiments we assume that the influence of other effects, such as temperature, are negligibly small. If we correct the δ¹³C values of G. inflata for a carbonate ion effect, the δ¹³C_shell and δ¹³C_DIC are correlated with an average offset of 2.11.     

Flow velocity affects internal oxygen conditions in the seagrass Cymodocea nodosa

The internal oxygen status of seagrass tissues, which is believed to play an important role in events of seagrass die-off, is partly determined by the rates of gas exchange between leaves and water column. In this study, we examined whether water column flow velocity has an effect on gas exchange, and hence on internal oxygen partial pressures (pO₂) in the Mediterranean seagrass, Cymodocea nodosa. We measured the internal pO₂ in the horizontal rhizomes of C. nodosa in darkness at different mainstream flow velocities, combined with different levels of water column oxygen pO₂ using an experimental flume in the laboratory. Flow velocity clearly had an effect on the internal oxygen status. In stagnant, but fully aerated water the mean internal pO₂ was 6.9 kPa, corresponding to about 30% of air saturation. The internal pO₂ increased with increasing flow velocity reaching saturation of around 12.2 kPa (60% of air saturation) at flow velocities ≥7 cm s⁻¹. Flow had a relatively larger influence on internal pO₂ at lower water column oxygen concentrations. By extrapolating linear relationships between internal and water column pO₂ in this experimental setup, rhizomes would become anoxic at a water column oxygen pO₂ of 4–4.5 kPa (∼20% of air saturation) in flowing water, but already at 6.4 kPa (∼30% of air saturation) in stagnant water. Water flow may play an important role for seagrass performance and survival in areas with poor water column oxygen conditions and may, in general, be of importance for the distribution of submerged rooted plants.     

Nitrogen fertilization and δ18O of CO2 have no effect on 18O‐enrichment of leaf water and cellulose in Cleistogenes squarrosa (C4) – is VPD the sole control?

The oxygen isotope composition of cellulose (δ¹⁸O_Cel) archives hydrological and physiological information. Here, we assess previously unexplored direct and interactive effects of the δ¹⁸O of CO₂ (δ¹⁸O_CO2), nitrogen (N) fertilizer supply and vapour pressure deficit (VPD) on δ¹⁸O_Cel, ¹⁸O‐enrichment of leaf water (Δ¹⁸O_LW) and cellulose (Δ¹⁸O_Cel) relative to source water, and p_exp_x, the proportion of oxygen in cellulose that exchanged with unenriched water at the site of cellulose synthesis, in a C₄ grass (Cleistogenes squarrosa). δ¹⁸O_CO2 and N supply, and their interactions with VPD, had no effect on δ¹⁸O_Cel, Δ¹⁸O_LW, Δ¹⁸O_Cel and p_exp_x. Δ¹⁸O_Cel and Δ¹⁸O_LW increased with VPD, while p_exp_x decreased. That VPD‐effect on p_exp_x was supported by sensitivity tests to variation of Δ¹⁸O_LW and the equilibrium fractionation factor between carbonyl oxygen and water. N supply altered growth and morphological features, but not ¹⁸O relations; conversely, VPD had no effect on growth or morphology, but controlled ¹⁸O relations. The work implies that reconstructions of VPD from Δ¹⁸O_Cel would overestimate amplitudes of VPD variation, at least in this species, if the VPD‐effect on p_exp_x is ignored. Progress in understanding the relationship between Δ¹⁸O_LW and Δ¹⁸O_Cel will require separate investigations of p_ex and p_x and of their responses to environmental conditions.     

Correlating δ13C and δ18O in cellulose of trees

We measured the carbon and oxygen isotopic composition of stem cellulose of Pinus sylvestris, Picea abies, Fagus sylvatica and Fraxinus excelsior. Several sites along a transect of a small valley in Switzerland were selected which differ in soil moisture conditions. At every site, six trees per species were sampled, and a sample representing a mean value for the period from 1940 to 1990 was analysed. For all species, the mean site δ¹³C and δ¹⁸O of stem cellulose are related to the soil moisture availability, whereby higher isotope ratios are found at drier sites. This result is consistent with isotope fractionation models when assuming enhanced stomatal resistance (thus higher δ¹³C of incorporated carbon) and increased oxygen isotope enrichment in the leaf water (thus higher δ¹⁸O) at the dry sites. δ¹⁸ O-δ¹³C plots reveal a linear relationship between the carbon and oxygen isotopes in cellulose. To interpret this relationship we developed an equation which combines the above-mentioned fractionation models. An important new parameter is the degree to which the leaf water enrichment is reflected in the stem cellulose. In the combined model the slope of the δ¹⁸O-δ¹³C plot is related to the sensitivity of the p_i/p_a of a plant to changing relative humidity.     

δ13C and stomatal number variability in the Cretaceous conifer Frenelopsis

The ¹³C/¹²C ratios of leaves of the conifer morphotype Frenelopsis were measured to decipher the influences of water and salt stress on stomatal density (SD), epidermal cell density (ECD) and stomatal index (SI). Three morphospecies were analyzed: F. ugnaensis from freshwater fluvio-lacustrine deposits (Upper Barremian), F. turolensis and alata from coastal deposits (Lower-Middle Albian and Upper Albian respectively). The cuticle δ¹³C values show a large variation from ? 28‰ to ? 21‰. Comparison with previously published marine carbonate δ¹³C records indicate that the difference in cuticle δ¹³C between the different deposits are mainly due to difference in CO₂-plant isotope fractionation rather than to change in isotopic composition of inorganic carbon in the atmosphere and ocean. The less negative δ¹³C and wide range in δ¹³C of F. turolensis and alata (? 27.5 to ? 21‰), compared to F. ugnaensis, (? 28 to ? 25‰) are interpreted as a result of salt and/or water stress. The data as a whole yield a good relationship between the ¹³C/¹²C ratio and SD (r = 0.67, n = 42, p < 0.001), SI (r = 0.53, n = 41, p < 0.001), hence suggesting that the differences in SD and SI between the three morphospecies are related to freshwater/saline environment. Looking at single morphospecies, the SD of F. ugnaensis decreases with increasing δ¹³C value (r = ? 0.57, n = 15, p = 0.026) as well as a decrease of SI (r = ? 0.62, n = 15, p = 0.013), possibly reflecting warmer and drier conditions. Average SI of F. alata does not significantly change with δ¹³C and inferred soil salinity in contrast to SD (p < 0.01).     

Dentine oxygen isotopes (δ18O) as a proxy for odontocete distributions and movements

Spatial variation in marine oxygen isotope ratios (δ¹⁸O) resulting from differential evaporation rates and precipitation inputs is potentially useful for characterizing marine mammal distributions and tracking movements across δ¹⁸O gradients. Dentine hydroxyapatite contains carbonate and phosphate that precipitate in oxygen isotopic equilibrium with body water, which in odontocetes closely tracks the isotopic composition of ambient water. To test whether dentine oxygen isotope composition reliably records that of ambient water and can therefore serve as a proxy for odontocete distribution and movement patterns, we measured δ¹⁸O values of dentine structural carbonate (δ¹⁸O_SC) and phosphate (δ¹⁸O_P) of seven odontocete species (n = 55 individuals) from regional marine water bodies spanning a surface water δ¹⁸O range of several per mil. Mean dentine δ¹⁸O_SC (range +21.2 to +25.5‰ VSMOW) and δ¹⁸O_P (+16.7 to +20.3‰) values were strongly correlated with marine surface water δ¹⁸O values, with lower dentine δ¹⁸O_SC and δ¹⁸O_P values in high‐latitude regions (Arctic and Eastern North Pacific) and higher values in the Gulf of California, Gulf of Mexico, and Mediterranean Sea. Correlations between dentine δ¹⁸O_SC and δ¹⁸O_P values with marine surface water δ¹⁸O values indicate that sequential δ¹⁸O measurements along dentine, which grows incrementally and archives intra‐ and interannual isotopic composition over the lifetime of the animal, would be useful for characterizing residency within and movements among water bodies with strong δ¹⁸O gradients, particularly between polar and lower latitudes, or between oceans and marginal basins.     

Physiological and isotopic signals in epilithic mosses for indicating anthropogenic sulfur on the urban–rural scale

The strength and source of anthropogenic sulfur (S) deposition is an important area of research in both environmental and ecological disciplines. Here S concentration, stable isotope (δ³⁴S) and photosynthetic pigments analyses were performed on epilithic mosses at Guiyang area (SW China) for investigating the distribution, origin and effect of urban-derived S at the urban–rural scale. Based on the variation of moss S, anthropogenic S was estimated to account for about 52% of total S in urban mosses and 35% in rural mosses within 30 km. The deposition of urban-derived S was biologically determined within 57 km from the urban center, but only 22% (about 24.4 × 10⁶ kg-S annually) reached over 30 km, with 78% (about 85.9 × 10⁶ kg-S) deposited within 30 km. δ³⁴S_moss signatures suggested the major source of anthropogenic S was still from coal combustion, and comparable δ³⁴S_moss values along the urban–rural transect suggested the inputs of urban-derived S into rural ecosystems. Unexpectedly, moss photosynthetic pigments did not show a decrease with S deposition, but express higher concentrations in the urban than in the rural. In contrast, correlations between moss photosynthetic pigments, and tissue nitrogen (N) and δ¹⁵N demonstrated a fertilizing effect of elevated N deposition on moss photosynthesis, which might buffer or offset the negative effect of S deposition on urban mosses. Collective evidences suggest that S% and δ³⁴S in epilithic mosses provided useful information for determining anthropogenic S deposition on the urban–rural scale, but moss photosynthetic pigments may not be applicable for reflecting S loading under high N deposition.     

Ecology and physiology of White River mammals based on stable isotope ratios of teeth

To characterize the ecology and physiology of common late Eocene–early Oligocene White River mammals, we analyzed the carbon and oxygen isotope composition of tooth enamel carbonate for six of the most abundant taxa: the perissodactyls Brontops (brontothere), Mesohippus (equid) and Subhyracodon (rhino); and the artiodactyls Merycoidodon (oreodont), Leptomeryx (leptomerycid) and Poebrotherium (camelid).δ¹³C values of middle and rear molars (M2s and M3s) and premolars range from ? 13.1‰ to ? 7.7‰ (V-PDB), consistent with pure C3 diets. In the late Eocene, Mesohippus, Merycoidodon, and Leptomeryx show indistinguishable average δ¹³C values (～ ? 10‰). In contrast, Brontops and Subhyracodon exhibit lower (? 11.2‰) and higher (? 8.7‰) values, respectively. Early Oligocene values for Mesohippus and Merycoidodon remain indistinguishable from each other and lower than the value of Leptomeryx, Poebrotherium, and Subhyracodon (～ ? 8.5‰). These results likely indicate niche separation in terms of habitat preference between the investigated sympatric taxa. More specifically, assuming a δ¹³C value of atmospheric CO₂ of ? 5.5‰, our data suggest a preference of Brontops for mesic forested areas, of Mesohippus and Merycoidodon for woodlands, and of Subhyracodon and Poebrotherium for more open habitats (e.g., grasslands). The higher Oligocene versus Eocene average δ¹³C exhibited by Leptomeryx possibly reflects a preference of the new Oligocene species L. evansi for more open and/or xeric habitats relative to the Eocene species L. speciosus.Late Eocene and early Oligocene average δ¹⁸O of Mesohippus, Merycoidodon, Leptomeryx, and Subhyracodon are similar (～ 25‰, V-SMOW), possibly indicating comparable water dependency for these taxa. In contrast, the higher δ¹⁸O of Poebrotherium (26.6‰) suggests lower water dependency whereas the lower δ¹⁸O of Brontops (23.0‰) may result from a high water dependency or, more likely, from its preference for humid habitats. Because hind-gut fermentation in perissodactyls requires high water intake, whereas fore-gut fermentation does not, our results might indicate the presence of fore-gut fermentation in early Oligocene camelids but its absence or incomplete development in late Eocene–early Oligocene oreodonts and leptomerycids.     

Comparison of carbonate C and O stable isotope records across the Jurassic/Cretaceous boundary in the Tethyan and Boreal Realms

Carbon and oxygen stable isotope records were compared for Jurassic/Cretaceous (J/K) boundary sections located in the Tethyan Realm (Brodno, Western Slovakia, and Puerto Escaño, Southern Spain; bulk limestones), and the Boreal Realm (Nordvik Peninsula, Northern Siberia, belemnites). Since a detailed biostratigraphic correlation of these Tethyan and Boreal sections is impossible due to different faunal assemblages, correlation of the isotope records was based on paleomagnetic data. This novel approach can improve our understanding of the synchroneity of individual isotope excursions in sections where detailed biostratigraphic correlation is impossible. No significant excursions in either the carbon or oxygen isotope records to be used for future Boreal/Tethyan correlations were found around the J/K boundary (the upper Tithonian and lower Berriasian; magnetozones M20n to M18n) in the studied sections. At the Nordvik section, where a much longer section (middle Oxfordian–basal Boreal Berriasian) was documented, the transition from the middle Oxfordian to the Kimmeridgian and further to the Volgian is characterized by a decrease in belemnite δ¹⁸O values (from δ¹⁸O values up to + 1.6‰ vs. V-PDB in the Oxfordian to values between + 0.3 and ? 0.8‰ in the late Volgian and earliest Boreal Berriasian). This trend, which has previously been reported from the Russian Platform and Tethyan Realm sections, corresponds either to gradual warming or a decrease in seawater δ¹⁸O. Supposing that the oxygen isotope compositions of seawater in the Arctic/Boreal and Tethyan Realms were similar, then the differences between oxygen isotope datasets for these records indicate differences in temperature. The Boreal/Tethyan temperature difference of 7–9 °C in the middle and late Oxfordian decreases towards the J/K boundary, indicating a significant decrease in latitudinal climatic gradients during the Late Jurassic. Two positive carbon isotope excursions recorded for the middle Oxfordian and upper Kimmeridgian in the Nordvik section can be correlated with a similar excursion described earlier for the Russian Platform. Minor influence of biofractionation at the carbon isotopes, and the influence of migration of belemnites to deeper, slightly cooler water at the oxygen isotopes, cannot be excluded for the obtained belemnite data.     

Oxygen and carbon isotope compositions of middle Cretaceous vertebrates from North Africa and Brazil: Ecological and environmental significance

In order to investigate mid-Cretaceous terrestrial climates of low paleolatitudes, Moroccan, Tunisian and Brazilian vertebrate apatites have been analyzed for their oxygen and carbon isotope compositions of phosphates (δ¹⁸O_p) and carbonates (δ¹⁸O_c, δ¹³C_c). At each site, coexisting theropod dinosaurs, titanosaurid sauropods, pterosaurs, crocodilians, turtles and fish have distinct δ¹⁸O_p and δ¹³C_c values reflecting their ecologies, diets and foraging environments. Oxygen isotope compositions of surface waters (δ¹⁸O_w) estimated from turtle and crocodile δ¹⁸O_p values range from − 5.0 ± 1.0‰ to − 2.4 ± 1.0‰, which do not differ from mean annual rainwater values occurring today under inter-tropical sub-arid to arid climates. High water temperatures ranging from 21 ± 6 °C to 34 ± 2 °C deduced from fish δ¹⁸O_p values are in agreement with those published for mid-Cretaceous low latitudes. Temporary or seasonal droughts are inferred from high δ¹⁸O_p values of lungfish teeth, even though lower reptile δ¹⁸O_p values suggest the use of distinct and most likely larger or regularly renewed bodies of water. Environmental conditions of the studied low latitude regions during the Aptian-Cenomanian interval were somewhat similar to those experienced today under semi-arid to arid tropical or equatorial climates, but with higher mean surface temperatures than present-day ones.     

The oxygen isotope composition of planktonic foraminifera from the Guaymas Basin,Gulf of California: Seasonal,annual, and interspecies variability

Sediment trap samples collected over a seven-year period (February 1991–October 1997) from Guaymas Basin in the Gulf of California were used to study the oxygen isotope composition of five species of planktonic foraminifera, Globigerinoides ruber (white), Globigerina bulloides, Neogloboquadrina dutertrei, Pulleniatina obliquiloculata, and Globorotalia menardii. The δ¹⁸O data were analyzed for temporal and interspecies variability and were compared to local hydrography to evaluate the use of each species in reconstructing past oceanographic applications. The two surface dwelling species, G. ruber and G. bulloides displayed the lowest δ¹⁸O values (～ 0.0 to ? 5.0‰), while δ¹⁸O values for the thermocline dwelling N. dutertrei, P. obliquiloculata, and G. menardii were higher (～ 0.0 to ? 2.0‰). The δ¹⁸O of G. ruber most accurately records measured sea surface temperatures (SSTs) throughout the year. G. bulloides δ¹⁸O tracks SSTs during the winter–spring upwelling period but for the remainder of the year records slightly colder, subsurface temperatures. The difference between the δ¹⁸O of the surface dwelling species, G. ruber and G. bulloides, and that of the thermocline dwelling species, N. dutertrei, P. obliquiloculata, and G. menardii, was used to estimate the surface to thermocline temperature gradient. During the winter these δ¹⁸O differences are small (～ 0.50‰) reflecting a well-mixed water column. These interspecies δ¹⁸O differences increase during the summer (～ 1.90‰) in response to the strong thermal stratification that exists at this time of year.