Changes in Sr/Ca, Ba/Ca and 87Sr/86Sr ratios between trophic levels in two forest ecosystems in the northeastern U.S.A.

The variability and biologicalfractionation of Sr/Ca, Ba/Ca and ⁸⁷Sr/⁸⁶Srratios were studied in a soil–plant–invertebrate–bird food chain in two forested ecosystems withcontrasting calcium availability in the northeasternU.S.A. Chemical measurements were made of the soilexchange pool, leaves, caterpillars, snails, and boththe femurs and eggshells of breeding insectivorousmigratory songbirds. ⁸⁷Sr/⁸⁶Sr values weretransferred up the food chain from the soil exchangepool to leaves, caterpillars, snails and eggshellswithout modification. Adult birds were the oneexception; their ⁸⁷Sr/⁸⁶Sr values generallyreflected those of lower trophic levels at each site,but were lower and more variable, probably becausetheir strontium was derived in part from foods intropical winter habitats where lower⁸⁷Sr/⁸⁶Sr ratios are likely to predominate. Sr/Ca and Ba/Ca ratios decreased at each successive trophiclevel, supporting previous suggestions that Sr/Ca andBa/Ca ratios can be used to identify the trophic levelat which an organism is primarily feeding. The changesin Sr/Ca and Ba/Ca ratios we measured for vegetationand insects were comparable to similar measurementsmade previously (but based on single samples of eachorganism) in an alpine ecosystem. Changes in Sr/Ca andBa/Ca ratios between birds and their food have notpreviously been measured, but the values we obtainedwere similar to those for herbivorous and carnivorousmammals at similar trophic levels. Our results provideevidence that supports the use of Sr/Ca ratios in thedetermination of human paleodiets and suggests thatSr/Ca ratios may also provide a useful tool in studiesof modern food webs. Furthermore, our findings suggestthat ⁹⁰Sr from nuclear fallout will notbioaccumulate in forests and that changes in Sr/Caratios between trophic levels will need to beconsidered in some cases when using⁸⁷Sr/⁸⁶Sr as a tracer of calciumbiogeochemistry.     

Distinguishing sources of base cations in irrigated and natural soils: evidence from strontium isotopes

Strontium isotope ratios (⁸⁷Sr/⁸⁶Sr) of soil solids, soil cation extracts, irrigation water and plant material are used to determine strontium and therefore cation sources and fluxes in irrigated and natural soil–plant systems. Strontium isotopes of soil solids from four soil profiles (two irrigated vineyard soils and two 'natural' profiles from nearby reserves) show large differences between soil horizons with depth. These differences are not reflected in ⁸⁷Sr/⁸⁶Sr ratios of soil labile cations, which show both little variation down-profile and much lower ratios than soil solids. In the undisturbed, natural soil profiles, labile cation ⁸⁷Sr/⁸⁶Sr ratios are close to the ratio of modern seawater, indicating that solutes of marine origin from precipitation are the primary input of strontium (and calcium) to the labile cation pool. In the irrigated soil profiles, ⁸⁷Sr/⁸⁶Sr ratios of labile cations are consistently shifted towards that of the irrigation water. Mass-balance calculations using ⁸⁷Sr/⁸⁶Sr ratios of the different inputs to the labile cation pool indicate more than 90% of labile strontium is derived from precipitation solutes in unirrigated soils, and up to 44% from irrigation water solutes as an additional source in irrigated soils. The ⁸⁷Sr/⁸⁶Sr ratios of grapes grown in irrigated soils match precisely with those of the labile soil cations, demonstrating that cation nutrients are drawn wholly from the labile cation pool and have the same mix of precipitation, irrigation, and soil solid sources. The ⁸⁷Sr/⁸⁶Sr ratios of grapes grown in the irrigated soils may therefore vary over time depending on (1) the changing mix of irrigation water and local precipitation and (2) potential change to irrigation water. These findings suggest limitations to the use of strontium isotopes in the tracing of grapes and wines to their soil of origin.     

青海喇家遗址人类遗骸的锶同位素比值分析

喇家遗址位于青海省民和县,主体为齐家文化的遗存,距今大约3900~4300年。喇家遗址古代人类迁移活动的研究,对于探索黄河上游古代文明,推动该地区齐家文化研究,有着积极的学术意义。本文首先采用电感耦合等离子体质谱技术对喇家遗址出土的22个个体的44份牙釉质和骨骼样品进行了元素分析,根据检测结果排除了受到污染的2份骨骼样品。其次,通过热电离质谱分析方法对喇家遗址出土22个个体的42份牙釉质和骨骼样品及8个猪牙釉质样品的锶同位素比值进行了测定。检测数据表明,猪牙釉质的锶同位素比值的标准偏差远小于其他动物,可以推断猪由当地饲养的可能性是最大的,因此其牙釉质锶同位素比值可以代表当地的锶同位素水平。经过计算得到8个猪牙釉质的锶同位素比值的平均值为0.710930,将该平均值加或减2倍标准偏差可以得到喇家遗址当地的锶同位素比值范围在0.711058~0.710802之间。以此为前提可以推测,本次检测的22个个体中,有17个个体牙釉质的锶同位素比值在遗址当地的锶同位素比值范围内,可能为本地出生。还有2个个体牙釉质在当地的锶同位素比值范围上下限附近,姑且存疑;仅有3个个体牙釉质的锶同位素比值在遗址当地的锶同位素比值范围以外,表明这些个体可能在其他地区出生,去世后埋葬在遗址中。此外,数据分析还显示,本地出生人群牙釉质的锶同位素比值平均值与骨骼的锶同位素比值平均值比较接近,暗示喇家遗址当地古人类生活方式可能比较统一。     

Use of foliar Ca/Sr discrimination and <Superscript>87</Superscript>Sr/<Superscript>86</Superscript>Sr ratios to determine soil Ca sources to sugar maple foliage in a northern hardwood forest

Calcium/strontium and ⁸⁷Sr/⁸⁶Sr ratios in foliage can be used to determine the relative importance of different soil sources of Ca to vegetation, if the discrimination of Ca/Sr by the plant between nutrient sources and foliage is known. We compared these tracers in the foliage of sugar maple (Acer saccharum) to the exchange fraction and acid leaches of soil horizons at six study sites in the White Mountains of New Hampshire, USA. In a previous study, sugar maple was shown to discriminate for Ca compared to Sr in foliage formation by a factor of 1.14 ± 0.12. After accounting for the predicted 14% shift in Ca/Sr, foliar Ca/Sr and ⁸⁷Sr/⁸⁶Sr ratios closely match the values in the Oie horizon at each study site across a 3.6-fold variation in foliar Ca/Sr ratios. Newly weathered cations, for which the Ca/Sr and ⁸⁷Sr/⁸⁶Sr ratios are estimated from acid leaches of soils, can be ruled out as a major Ca source to current foliage. Within sites, the ⁸⁷Sr/⁸⁶Sr ratio of the soil exchange pool in the Oa horizon and in the 0–10 cm and 10–20 cm increments of the mineral soil are similar to the Oie horizon and sugar maple foliar values, suggesting a common source of Sr in all of the actively cycling pools, but providing no help in distinguishing among them as sources to foliage. The Ca/Sr ratio in the soil exchange pool, however, decreases significantly with depth, and based on this variation, the exchange pool below the forest floor can be excluded as a major Ca source to the current sugar maple foliage. This study confirms that internal recycling of Ca between litter, organic soil horizons and vegetation dominate annual uptake of Ca in northern hardwood ecosystems. Refinement of our understanding of Ca and Sr uptake and allocation in trees allows improvement in the use of Ca/Sr and ⁸⁷Sr/⁸⁶Sr ratios to trace Ca sources to plants.     

Identifying calcium sources at an acid deposition-impacted spruce forest: a strontium isotope,alkaline earth element multi-tracer approach

Depletion of calcium from forest soils has important implications for forest productivity and health. Ca is available to fine feeder roots from a number of soil organic and mineral sources, but identifying the primary source or changes of sources in response to environmental change is problematic. We used strontium isotope and alkaline earth element concentration ratios of trees and soils to discern the record of Ca sources for red spruce at a base-poor, acid deposition-impacted watershed. We measured ⁸⁷Sr/⁸⁶Sr and chemical compositions of cross-sectional stemwood cores of red spruce, other spruce tissues and sequential extracts of co-located soil samples. ⁸⁷Sr/⁸⁶Sr and Sr/Ba ratios together provide a tracer of alkaline earth element sources that distinguishes the plant-available fraction of the shallow organic soils from those of deeper organic and mineral soils. Ca/Sr ratios proved less diagnostic, due to within-tree processes that fractionate these elements from each other. Over the growth period from 1870 to 1960, ⁸⁷Sr/⁸⁶Sr and Sr/Ba ratios of stemwood samples became progressively more variable and on average trended toward values that considered together are characteristic of the uppermost forest floor. In detail the stemwood chemistry revealed an episode of simultaneous enhanced uptake of all alkaline earth elements during the growth period from 1930 to 1960, coincident with reported local and regional increases in atmospheric inputs of inorganic acidity. We attribute the temporal trends in stemwood chemistry to progressive shallowing of the effective depth of alkaline earth element uptake by fine roots over this growth period, due to preferential concentration of fine roots in the upper forest floor coupled with reduced nutrient uptake by roots in the lower organic and upper mineral soils in response to acid-induced aluminum toxicity. Although both increased atmospheric deposition and selective weathering of Ca-rich minerals such as apatite provide possible alternative explanations of aspects of the observed trends, the chemical buffering capacity of the forest floor-biomass pool limits their effectiveness as causal mechanisms.     

Do deep tree roots provide nutrients to the tropical rainforest?

The contribution of deep tree roots to the nutrition of a tropicalrainforest were studied along an edaphic transect in French Guyana. Soil typeswere mapped in relation to the texture of the upper horizons and the depth ofoccurrence of the loamy saprolite. The position of mature individuals of fourcommon species, differing by they rooting depth, was identified and tree leaveswere analysed for major nutrients and strontium (Sr) isotopic ratios.On average, the range of leaf isotopic ratio (⁸⁷Sr/⁸⁶Sr= 0.714–0.716) was narrow compared to that of bulk soils(⁸⁷Sr/⁸⁶Sr = 0.72–0.77). Steep gradients ofincreasing ⁸⁷Sr/⁸⁶Sr in roots with soil depth were foundin all investigated profiles, which indicated that the flux of Sr deposited inrain and leached from the litter layer was tightly retained in the upper soillayers. Over the whole of the site, as well as within each soil unit, tree⁸⁷Sr/⁸⁶Sr ratios were very similar whatever the species,and close to litter and near-surface roots ⁸⁷Sr/⁸⁶Srratios, suggesting no or very little Sr contribution from deep tree roots.Variations of Ca and Sr concentrations in leaves were strongly correlated butnot with leaf ⁸⁷Sr/⁸⁶Sr ratios. These results support thetheory that Sr and Ca uptake and cycling are mostly superficial in tropicalrainforests.     

Tagging the next generation: validation of trans-generational chemical tagging for an endangered fish

In this study we validated marking offspring through peritoneal injection of ripe females using two concentrations of strontium (strontium chloride hexahydrate). Larvae from treatments were monitored for condition morphometrics and tested for chemical mark incorporation in their otoliths via laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) to quantify the strontium concentration (Sr/Ca) and laser ablation multi-collector inductively coupled plasma mass spectrometry (LA-MC-ICPMS) to measure the strontium isotope ratios (⁸⁷Sr:⁸⁶Sr) of otoliths. Otolith strontium concentrations and strontium isotopes ratios were elevated in the high-concentration treatment, while the low-concentration and control treatments were not significantly different from each other. Larval size and eye diameter at hatch were similar among treatments; however, yolk and oil globule diameters were significantly reduced in the high-concentration treatment. Moreover, growth rates after 60?days post-hatch were significantly reduced in the high-concentration treatment relative to the low-concentration and control treatments, suggesting trans-generational tagging can have deleterious effects on offspring. Our study provides evidence for the efficacy of artificially marking offspring via injection of strontium into ripe females and could provide new tools for managing endangered fish populations; however, careful consideration of chemical concentrations and dosages may be required prior to its application in a fisheries management experiment.     

Variations of bioavailable Sr concentration and 87Sr/86Sr ratio in boreal forest ecosystems

The mean depth of Sr and water uptake in mixed Norway spruce (Picea abies) and Scots pine (Pinus sylvestris) stands was investigated, using natural variations of ⁸⁷Sr/⁸⁶Sr and ¹⁸O/¹⁶O in soils in relation to depth. Three spruce-pine pairs were studied on a podzol and a peat site in Northern Sweden. Tree leaf and wood, as well as soils, soil solutions and roots below each tree were analysed for Sr and Ca concentrations and ⁸⁷Sr/⁸⁶Sr ratio. The ¹⁸O/¹⁶O ratio was also determined in xylem sap and soil solutions in relation to depth. Soil solution ¹⁸O/¹⁶O decreased in relation to depth. Comparing with xylem sap ¹⁸O/¹⁶O data indicated a deeper uptake of soil water by pine than spruce on the podzol site and a superficial uptake by both species on the peat. The ⁸⁷Sr/⁸⁶Sr ratio of bioavailable Sr generally increased in soils in relation to depth. Contrastingly, the ⁸⁷Sr/⁸⁶Sr ratio in spruce wood was generally higher than in pine wood suggesting a deeper uptake of Sr by spruce. But the ⁸⁷Sr/⁸⁶Sr ratio and concentrations of bioavailable Sr were systematically higher below spruce than below pine. In order to explain these unexpected results, we built a simple flux model to investigate the possible effects of interspecific variations in Sr cycling, soil mineral weathering and depth of Sr uptake on soil and tree ⁸⁷Sr/⁸⁶Sr ratio. At the study sites, spruce cycled in litterfall up to 12 times more strontium than pine. The use of the model showed that this difference in Sr cycling could alone explain higher isotopic signatures of trees and topsoils below spruce. Besides, high isotopic signatures of roots in the A/E horizons below spruce led us to hypothesise a species-specific weathering process. Finally, the comparison between the ⁸⁷Sr/⁸⁶Sr ratios in wood and root or soil solutions below each species suggested that the average depth of Sr and water uptake were close, but irregular variations of the Sr isotopic ratio with depth reduce the accuracy of the results. Tree species strongly influence Sr isotopic ratios in boreal forest soils through differences in Sr cycling, and possibly through specific mineral weathering.     

The relative uptake of Ca and Sr into tree foliage using a whole-watershed calcium addition

The use of strontium isotopes and ratios of alkaline earth elements (i.e., ⁸⁷Sr/⁸⁶Sr and Ca/Sr) to trace Ca sources to plants has become common in ecosystem studies. Here we examine the relative uptake of Ca and Sr in trees and subsequent accumulation in foliage. Using a whole-watershed Ca addition experiment at the Hubbard Brook Experimental Forest in N.H., we measured the uptake of Ca relative to Sr in foliage and roots of sugar maple (Acer saccharum), yellow birch (Betula alleghaniensis), American beech (Fagus grandifolia), and red spruce (Picea rubens). Vegetation was analyzed for Ca and Sr concentrations and the ⁸⁷Sr/⁸⁶Sr ratio. A comparison of the Ca/Sr ratio in the vegetation and the Ca/Sr ratio of the applied mineral allows for the calculation of a discrimination factor, which defines whether Ca and Sr are incorporated and allocated in the same ratio as that which is available. A discrimination factor greater than unity indicates preferential uptake of Ca over Sr; a factor less than unity reflects preferential uptake of Sr over Ca. We demonstrate that sugar maple (SM) and yellow birch (YB) have similar and small discrimination factors (1.14 ± 0.12,1σ and 1.16 ± 0.09,1σ) in foliage formation and discrimination factors of less than 1 in root formation (0.55–0.70). Uptake into beech suggests a larger discrimination factor (1.9 ± 1.2) in foliage but a similar root discrimination factor to SM and YB (0.66 ± 0.06,1σ). Incorporation into spruce foliage occurs at a much slower rate than in these other tree species and precludes evaluation of Ca and Sr discrimination in spruce foliage at this time. Understanding the degree to which Ca is fractionated from Sr in different species allows for refinement in the use of ⁸⁷Sr/⁸⁶Sr and Ca/Sr ratios to trace Ca sources to foliage. Methods from this study can be applied to natural environments in which various soil cation pools have different ⁸⁷Sr/⁸⁶Sr and Ca/Sr ratios. The results reported herein have implications for re-evaluating Ca sources and fluxes in forest ecosystems.     

Seawater strontium isotope curve at the Silurian/Devonian boundary: a study of the global Silurian/Devonian boundary stratotype

Present application of ⁸⁷Sr/⁸⁶Sr chemostratigraphy to detailed stratigraphical tasks is limited by inaccurate calibration of the general seawater strontium curve to absolute as well as to relative time scales. For this reason, refinement of the general seawater strontium curve has been suggested, using mainly clearly defined global boundary stratotype sections. This study reports the first ⁸⁷Sr/⁸⁶Sr data from the global Silurian/Devonian boundary stratotype section and fills an existing 1-Ma gap in available data. Generally, the data from the stratotype fit the range interpolated from published ⁸⁷Sr/⁸⁶Sr data of the general curve, but the slight differences may suggest an existence of a high-order oscillation near the Silurian/Devonian boundary. Higher ⁸⁷Sr/⁸⁶Sr values in the Devonian part of boundary bed 20 (20-beta) may indicate an exotic material influx of recycled sediment.     

Long-term records of strontium isotopic composition in tree rings suggest changes in forest calcium sources in the early 20th century

Many studies made in Europe and North America have shown an increasing depletion of exchangeable base cations that may cause tree nutritional deficiencies in sensitive soils. We use radial variation of strontium isotope in tree-rings (⁸⁷Sr/⁸⁶Sr ratio) to monitor possible changes in Ca sources for tree nutrition (Sr is used as an analog to Ca). The two main sources of Ca in forest stands are mineral weathering release and atmospheric inputs. Measurements in several forest stands in temperate regions show a steep decrease from pith to outer wood of the Sr isotope ratio from∼1870 to∼1920 except for stands developed on soils with a higher Ca status. This suggests a decrease of the weathering contribution (high ⁸⁷Sr/⁸⁶Sr ratio) when cations are displaced from the soil exchange complex by acid deposition at a rate faster than the replenishment of the cation pool by mineral weathering. This displacement enhances the atmospheric contribution, which is characterized by a low ⁸⁷Sr/⁸⁶Sr ratio. Tree-ring chronologies are an exceptional historic-timing record of chemical changes in the soil environment induced by atmospheric pollution. The reliability of the tree-ring recorder has been verified with a well-controlled nutritional perturbation in the context of a limed forest stand (with a known liming Sr isotopic signature). Our data suggest that forest ecosystems were affected by atmospheric inputs of strong acids earlier than previously thought.     

Bone strontium in pregnant and lactating females from archaeological samples

Because plants and animals consume or absorb different amounts of strontium and calcium, anthropologists are able to use strontium/calcium (Sr/Ca) ratios from archaeologically recovered human bone to estimate the relative contributions of meat and plants to paleodiets. Often females exhibit higher Sr/Ca ratios than males, a fact usually attributed to lower meat intake among women. However, in vivo and in vitro experiments with laboratory animals show that pregnancy and lactation elevate maternal bone strontium and depress maternal bone calcium because 1) strontium is discriminated against in favor of calcium in the transport of ions to the placenta and mammary glands and 2) pregnancy and lactation facilitate absorption of alkaline earth metals from the gut. In this study, bone Sr/Ca ratios and strontium concentrations were compared between reproductive-age females, postmenopausal females, and adult males from two late prehistoric Native American sites in Georgia: the King site (N = 43) and the Etowah site (N = 51). At the King site, the mean Sr/Ca ratio of females was over 14% greater than that of males. At Etowah, the mean strontium level of reproductive-age females exceeded that of postmenopausal females by almost 25%. Most of the difference, it is argued, is due to pregnancy and lactation. A dietary preference among pregnant and lactating women for foods high in alkaline earths, particularly nuts and corn, may also be partially responsible. Until we assess the influence variables other than nutrition exert on trace element concentrations, our reconstructions of paleodiets will be suspect.     

Application of otolith microchemistry to estimate the migratory history of Japanese eel Anguilla japonica on the Sanriku Coast of Japan

The age and migratory history of the Japanese eel, Anguilla japonica Temminck & Schlegel, collected in Miyako Bay along the Sanriku coast of Japan, was examined using the otolith microstructure and analysis of strontium (Sr) and calcium (Ca) concentrations conducted with wavelength dispersive X‐ray spectrometry by an electron microprobe. The line analysis of Sr : Ca ratios along the life history transect of each otolith showed a peak (ca. 15–17 × 10^?3) which corresponded with the period of their leptocephalus and early glass eel stages in the ocean. The mean Sr : Ca ratios from the elver mark to the otolith edge indicated that there were eels with several general categories of migratory history, including sea eels that never entered freshwater (average Sr : Ca ratios, ≥6.0 × 10^?3), and others that entered freshwater for brief periods but returned to the estuary or bay. This evidence of the occurrence of sea eels in this northern area indicates that Japanese eels of the Sanriku coast do not necessarily migrate into freshwater rivers during recruitment as do glass eels at the beginning of their growth phase; even those that do enter freshwater may later return to the marine environment. Thus, anguillid eel migrations into freshwater are clearly not an obligatory migratory pathway, but rather a facultative catadromy with seawater or estuarine residents as an ecophenotype.     

Strontium isotope analyses of large herbivore habitat use in the Cape Fynbos region of South Africa

The Cape Fynbos region of South Africa, a global biodiversity hotspot, hosted a diverse large mammal fauna till shortly after permanent European settlement (1652). How these animals survived in this exceptionally nutrient-poor environment is puzzling and it is generally believed that they restricted their movements to the more fertile shale areas. We tested the hypothesis that large herbivores avoid nutrient-poor limestone and sandstone fynbos shrublands in favour of shale-derived renosterveld vegetation using strontium (Sr) isotope analysis. If this technique could reconstruct the preferred feeding habitats of the contemporary fauna, it might also be useful for reconstructing the preferred feeding grounds of an extinct fauna. Using the assumption that small rodents have spatially restricted foraging activities, we determined the ⁸⁷Sr/⁸⁶Sr isotope ratios of rodent teeth to establish the isotopic signal characteristic of the different geological substrates in the area. We then analysed ⁸⁷Sr/⁸⁶Sr isotope ratios in the bones of a number of different large herbivores found in De Hoop Nature Reserve using laser ablation multi-collector inductively coupled plasma mass spectrometry. These values were compared to the bioavailable (rodent) values on the respective geological substrates. The technique identified differences in feeding substrate selection between different species and groups of the same species. The results also showed that shale renosterveld shrubland is not the exclusive source of nutrition for the large herbivores. Strikingly different isotope ratios among individuals in some populations pointed to significant dispersal events from distant sources. However, we were unable to pinpoint the exact feeding areas using Sr isotope analysis probably because some animals use a combination of substrates for feeding and because the geology of the study area is complex with graded isotope signals. We suggest that this technique is a valuable additional tool for exploring large mammal foraging behaviour on habitats associated with contrasting and less complex geology.     

Diversity of life strategies of pikepech <Emphasis Type="Italic">Sander lucioperca</Emphasis> (L.) in the Lower Volga (by the data of microelement composition of otolithes)

Strontium (Sr) and calcium (Ca) contents and Sr/Ca ratios in otoliths of pikeperch Sander lucioperca have been studied by X-ray fluorescent microanalysis. A sample of 95 specimens from the Lower Volga region are studied. The fish were obtained in a section of the Akhtuba River at a distance of 250–279 km upstream from the Caspian Sea. Some specimens in the sample have low strontium content throughout the otolith. The other fish have increased both Sr content and Sr/Ca ratios in core zones of otolith or near its outer edge: the Sr/Ca ratio is over 6.00 × 10^–3, with a maximum at 10.02 × 10^–3. The fish with a low Sr/Ca ratio live in freshwater and demonstrate a resident life history strategy. Pikeperch that have increased ratios of Sr/Ca in outer zones of otolith demonstrate a migratory life history strategy. These fish leave the freshwater of the Volga and feed in brackish water of the Northern Caspian Sea. Some migratory fish migrate to the sea as underyearlings, stay in a brackish water for 1 year or less, and then return back to fresh water for the rest of its life. The other group migrates back and forth from freshwater to the sea several times during their life. Finally, some fish leave freshwater for 1–2 years, spending this time in the Northern Caspian Sea. The conclusion is that the pikeperch stock in the Lower Volga has a complicated composition and consists of freshwater (residents and rheodromic ones) and migratory (anadromous and semianadromous) fish.     

Strontium isotopes (87Sr/86Sr) in terrestrial ecological and palaeoecological research: empirical efforts and recent advances in continental‐scale models

Strontium (Sr) isotope analysis can provide detailed biogeographical and ecological information about modern and ancient organisms. Because Sr isotope ratios (⁸⁷Sr/⁸⁶Sr) in biologically relevant materials such as water, soil, vegetation, and animal tissues predominantly reflect local geology, they can be used to distinguish geologically distinct regions as well as identify highly mobile individuals or populations. While the application of Sr isotope analysis to biological research has been steadily increasing, high analytical costs have prohibited more widespread use. Additionally, accessibility of this geochemical tool has been hampered due to limited understanding of (i) the degree to which biologically relevant materials differ in their spatial averaging of ⁸⁷Sr/⁸⁶Sr ratios, and (ii) how these differences may be affected by lithologic complexity. A recently developed continental‐scale model that accounts for variability in bedrock weathering rates and predicts Sr isotope ratios of surface water could help resolve these questions. In addition, if this ‘local water’ model can accurately predict ⁸⁷Sr/⁸⁶Sr ratios for other biologically relevant materials, there would be reduced need for researchers to assess regional Sr isotope patterns empirically. Here, we compile ⁸⁷Sr/⁸⁶Sr data for surface water, soil, vegetation, and mammalian and fish skeletal tissues from the literature and compare the accuracy with which the local water model predicts Sr isotope data among these five materials across the contiguous USA. We find that measured Sr isotope ratios for all five materials are generally close to those predicted by the local water model, although not with uniform accuracy. Mammal skeletal tissues are most accurately predicted, particularly in regions with low variability in ⁸⁷Sr/⁸⁶Sr predicted by the local water model. Increasing regional geologic heterogeneity increases both the offset and variance between modelled and empirical Sr isotope ratios, but its effects are broadly similar across materials. The local water model thus provides a readily available source of background data for predicting ⁸⁷Sr/⁸⁶Sr for biologically relevant materials in places where empirical data are lacking. The availability of increasingly high‐quality modelled Sr data will dramatically expand the accessibility of this geochemical tool to ecological applications.     

Strontium isotope record of the Hygophum hygomii otoliths from the European middle Miocene

⁸⁷Sr/⁸⁶Sr values from otoliths of the worldwide-distributed fish Hygophum hygomii are used for the purpose of isotope chemostratigraphy. In order to evaluate the potential of H. hygomii otoliths for strontium (Sr) isotopic studies, we first compare the ⁸⁷Sr/⁸⁶Sr ratio of current representatives of the species with that of modern sea water. Then, three fossil otoliths of H. hygomii collected in middle Miocene sediments of the Aquitaine Basin (Lafaurie locality, SW France) and the Carpathian Foredeep of the Central Paratethys (Brno-Kralovo Pole locality, SE Czech Republic) are analysed. The age inferred from the ⁸⁷Sr/⁸⁶Sr ratio at Lafaurie places the two analysed otoliths within the time interval of 15.5–15.1 Ma. This time interval matches the published early Langhian age obtained from the ⁸⁷Sr/⁸⁶Sr ratio of bivalves measured at the same locality. At the Brno-Kralovo Pole, the ⁸⁷Sr/⁸⁶Sr ratio of the analysed otolith returns a wider timespan of 14.78–13.10 Ma, falling into an interval of poor time resolution of the ⁸⁷Sr/⁸⁶Sr chemostratigraphy. Comparisons with published biostratigraphic and paleoclimatic data suggest that the analysed fossil otoliths of H. hygomii were mineralized during the late part of the Langhian, at ∼14.2 Ma. This work represents a first attempt to use otoliths for ⁸⁷Sr/⁸⁶Sr chemostratigraphy, and indicates that such a use may represent a powerful tool for testing stratigraphic correlations in the future.     

Lead concentrations and lead and strontium stable-isotope ratios in teeth of European roe deer (Capreolus capreolus)

The study reports lead concentrations and lead and strontium stable-isotope ratios in mandibular molars of roe deer from three different areas in western Germany. Lead concentrations in third molars ranged between 0.23 and 36.61 μg/g (dry weight). Comparing lead concentrations in first molars and third molars in a group of ca. 1.5- or ca. 2.5-year-old individuals from the same area revealed an effect of tooth age on tooth lead content. The higher lead concentrations in the first molars were attributed to the longer period of lead accumulation by the dentin of these teeth compared with the later-forming third molars. Differences in lead isotopic signatures of the teeth were observed between the three areas, presumably reflecting variation in exposure to different sources of environmental lead. We also found marked variation in the ⁸⁷Sr/⁸⁶Sr isotope ratios of the teeth, with only a small overlap in values between two of the areas. Strontium isotope analysis alone or in combination with lead isotope analyses can be a useful means of assessing the provenance of deer teeth of unknown geographical origin.     

Environmental signature in the otolith elemental fingerprint of the tapertail anchovy, Coilia mystus, from the Changjiang estuary, China

The ontogenetic patterns of habitat use and the migratory history of the tapertail anchovy, Coilia mystus, collected in the Changjiang estuary around Chongming Island, China, were studied by examining the environmental signature in the otolith strontium (Sr) and calcium (Ca) fingerprints using electron probe microanalysis (EPMA). Our results suggest that the migration strategy of C. mystus is much more flexible than supposed in the literature to date. The spring spawning population of C. mystus from the studied area was found to consist of individuals with different migration histories. Although the tapertail anchovy seems to be an anadromous fish that spawns and hatches in a freshwater habitat, it can also use a freshwater environment in non‐spawning seasons. The otolith EPMA of the elemental fingerprint (Sr x‐ray maps and Sr : Ca ratios) is an environmental indicator that can be applied to the migratory ecology of other important diadromous species in China.