Isotopic records of terrestrial ice age environments in mammoth bioapatite

Palaeoenvironments of the latter half of the Weichselian ice age and the transition to the Holocene, from ca. 52 to 4 ka, were investigated using isotopic analysis of oxygen, carbon and strontium in mammal skeletal apatite. The study material consisted predominantly of subfossil bones and teeth of the woolly mammoth (Mammuthus primigenius Blumenbach), collected from Europe and Wrangel Island, northeastern Siberia. All samples have been radiocarbon dated, and their ages range from >52 ka to 4 ka. Altogether, 100 specimens were sampled for the isotopic work. In Europe, the studies focused on the glacial palaeoclimate and habitat palaeoecology. To minimise the influence of possible diagenetic effects, the palaeoclimatological and ecological reconstructions were based on the enamel samples only. The results of the oxygen isotope analysis of mammoth enamel phosphate from Finland and adjacent nortwestern Russia, Estonia, Latvia, Lithuania, Poland, Denmark and Sweden provide the first estimate of oxygen isotope values in glacial precipitation in northern Europe. The glacial precipitation oxygen isotope values range from ca. -9.2±1.5 in western Denmark to -15.3 in Kirillov, northwestern Russia. These values are 0.6-4.1 lower than those in present-day precipitation, with the largest changes recorded in the currently marine influenced southern Sweden and the Baltic region. The new enamel-derived oxygen isotope data from this study, combined with oxygen isotope records from earlier investigations on mammoth tooth enamel and palaeogroundwaters, facilitate a reconstruction of the spatial patterns of the oxygen isotope values of precipitation and palaeotemperatures over much of Europe. The reconstructed geographic pattern of oxygen isotope levels in precipitation during 52-24 ka reflects the progressive isotopic depletion of air masses moving northeast, consistent with a westerly source of moisture for the entire region, and a circulation pattern similar to that of the present-day. The application of regionally varied δ/T-slopes, estimated from palaeogroundwater data and modern spatial correlations, yield reasonable estimates of glacial surface temperatures in Europe and imply 2-9°C lower long-term mean annual surface temperatures during the glacial period. The isotopic composition of carbon in the enamel samples indicates a pure C3 diet for the European mammoths, in agreement with previous investigations of mammoth ecology. A faint geographical gradient in the carbon isotope values of enamel is discernible, with more negative values in the northeast. The spatial trend is consistent with the climatic implications of the enamel oxygen isotope data, but may also suggest regional differences in habitat openness. The palaeogeographical changes caused by the eustatic rise of global sea level at the end of the Weichselian ice age was investigated on Wrangel Island, using the strontium isotope (Sr-87/Sr-86) ratios in the skeletal apatite of the local mammoth fauna. The diagenetic evaluations suggest good preservation of the original Sr isotope ratios, even in the bone specimens included in the study material. To estimate present-day environmental Sr isotope values on Wrangel Island, bioapatite samples from modern reindeer and muskoxen, as well as surface waters from rivers and ice wedges were analysed. A significant shift towards more radiogenic bioapatite Sr isotope ratios, from 0.71218 ± 0.00103 to 0.71491 ± 0.00138, marks the beginning of the Holocene. This implies a change in the migration patterns of the mammals, ultimately reflecting the inundation of the mainland connection and isolation of the population. The bioapatite Sr isotope data supports published coastline reconstructions placing the time of separation from the mainland to ca. 10-10.5 ka ago. The shift towards more radiogenic Sr isotope values in mid-Holocene subfossil remains after 8 ka ago reflects the rapid rise of the sea level from 10 to 8 ka, resulting in a considerable reduction of the accessible range area on the early Wrangel Island.Tämä tutkimus käsittelee ympäristöoloja Veiksel-jääkauden jälkipuoliskolla ja nykyisen lämpökauden, Holoseenin, alussa 52 000-4 000 vuotta sitten käyttäen hyväksi luustoapatiitin, enimmäkseen villakarvamammutin (Mammuthus primigenius Blumenbach) poskihampaiden hammaskiilteen, isotooppikoostumuksia. Yhteensä 100 luustoapatiittinäytettä analysoitiin hapen, hiilen ja strontiumin isotooppikoostumusten suhteen. Tutkimukset kohdentuivat Eurooppaan ja Itä-Siperian edustalla Jäämeressä sijaitsevaan Wrangelin saareen. Euroopassa tutkimukset keskittyivät muinaiseen ilmastoon ja mammuttien elinympäristöön, joita selvitettiin happi- ja hiili-isotooppien avulla. Suomesta, Luoteis-Venäjältä, Virosta, Latviasta, Liettuasta, Puolasta, Ruotsista ja Tanskasta löytyneiden poskihammasnäytteiden kiilteen happi-isotooppikoostumuksen perusteella pystyttiin määrittämään jääkautisen sadannan happi-isotooppiarvo Pohjois-Euroopassa noin 52 000-24 000 vuotta sitten, ja edelleen arvioimaan alueen keskimääräisiä vuotuisia lämpötiloja. Saadut tulokset tarjoavat ensimmäiset arviot jääkausiaikaisen ilmaston lämpötiloista alueella ja viittaavat selviin alueellisiin eroihin muutoksen voimakkuudessa jääkausiaikaisen ja nykyisen ilmaston välillä. Alueesta riippuen happi-isotooppiarvojen perusteella arvioidut vuosittaiset keskilämpötilat jääkausiajalla olivat 2-9°C nykyisiä lämpötiloja alempia. Työssä tuotetun uuden happi-isotooppiaineiston yhdistäminen aikaisempiin tutkimustuloksiin mahdollisti ensimmäistä kertaa jääkausiajan sadannan happi-isotooppiarvojen maantieteellisen jakauman rekonstruoimisen koko läntisen Euroopan alueella. Jääkautisen sadannan happi-isotooppiarvot ovat korkeimmat lounaassa, ja muuttuvat jatkuvasti matalammiksi koillista kohden kuvastaen läntistä kosteuslähdettä ja ilmamassojen kulkua lounaasta koilliseen. Näin ollen tutkimuksen tulokset viittaavat siihen, että Euroopan sadannan kosteuslähteet ja ilmakehän suurimittakaavainen liike ovat pysyneet samankaltaisina viimeisen ~50 000 vuoden ajan. Rekonstruoitua jääkausiaikaisen sadannan happi-isotooppikarttaa voidaan käyttää hyödyksi tarkistettaessa globaalisten ja alueellisten ilmastomallien toimivuutta. Eurooppalaisten hammaskiillenäytteiden hiili-isotooppikoostumus viittaa puhtaasti C3-kasvillisuudesta koostuneeseen ravintoon. Arvoissa nähtävä heikko maantieteellinen gradientti on yhtäpitävä happi-isotooppiarvoissa ilmentyvän ilmastogradientin kanssa, mutta saattaa myös viitata maantieteellisiin eroihin mammuttien elinympäristön avoimuudessa. Hiili-isotooppiarvot mahdollistavat tulkinnan, jonka mukaan elinympäristöt idässä ja koillisessa olisivat olleet suljetumpia verrattuna läntisempiin elinympäristöihin. Veiksel-jääkauden lopulla jäätikköjen sulamisesta aiheutuneen merenpinnan nousun vaikutuksia tutkittiin Wrangelin saarelta löytyneiden jääkausifaunan luustojäänteiden strontiumisotooppikoostumuksen (Sr-87/Sr-87) avulla. Holoseeni-epookin alussa, noin 10 000 vuotta sitten, eläinten luuston strontiumisotooppisuhteessa tapahtui selvä muutos. Ajanjaksoon >50 000-11 000 vuotta sitten ajoitettujen näytteiden Sr-isotooppisuhde eroaa selvästi Holoseeniin ajoitettuihin (9900-4000 vuotta sitten) näytteisiin verrattuna. Muutos korkeampiin Sr-isotooppiarvoihin heijastaa muutosta eläinten käyttämissä laidunnusalueissa ja lopulta merenpinnan noususta aiheutunutta Wrangelin saaren irtikuroutumista mantereesta. Luustoapatiitin strontiumisotooppiarvot viittaavat siihen, että maayhteys on katkennut 10 000-10 500 vuotta sitten, ja näin ollen tarkentavat aikaisempia, merenpintakäyriin ja syvyyskarttoihin perustuneita arvioita saaren eristymisestä

Source of strontium in archaeological mobility studies—marine diet contribution to the isotopic composition

The strontium isotope composition of human tissues is widely used in archaeological mobility studies. However, little attention is paid to the relative contributions of terrestrial versus marine sources of strontium in these studies. There is some debate over the role of a solid diet versus drinking water as the most important source of strontium for the human body, with related possibilities of misinterpretation of the archaeological record if only strontium isotope compositions of the biosphere are studied. However, there is a third component, marine strontium, which is commonly not assumed to contribute towards the strontium isotope composition of archaeological skeletal remains, especially in locations that are not directly coastal. To illustrate the potentially obfuscating effects of mixed Sr sources in a human population, we present a case study of twelve individuals from the medieval Finnish site Iin Hamina with a known dietary history. Our study shows that marine consumption is a significant factor explaining the strontium isotope composition of the Iin Hamina human remains, with implication of erroneous conclusions about immigration without prior knowledge of diet composition. Thus, future studies should always incorporate a rigorous analysis of dietary history, with special regard to potential consumption of aquatic resources, when strontium isotope analysis is used as a method in the study of palaeomobility

You eat what you find - Local patterns in vegetation structure control diets of African fungus-growing termites

Fungus-growing termites and their symbiotic Termitomyces fungi are critically important carbon and nutrient recyclers in arid and semiarid environments of sub-Saharan Africa. A major proportion of plant litter produced in these ecosystems is decomposed within nest chambers of termite mounds, where temperature and humidity are kept optimal for the fungal symbionts. While fungus-growing termites are generally believed to exploit a wide range of different plant substrates, the actual diets of most species remain elusive. We studied dietary niches of two Macrotermes species across the semiarid savanna landscape in the Tsavo Ecosystem, southern Kenya, based on carbon (C) and nitrogen (N) stable isotopes in Termitomyces fungus combs. We applied Bayesian mixing models to determine the proportion of grass and woody plant matter in the combs, these being the two major food sources available for Macrotermes species in the region. Our results showed that both termite species, and colonies cultivating different Termitomyces fungi, occupied broad and largely overlapping isotopic niches, indicating no dietary specialization. Including laser scanning derived vegetation cover estimates to the dietary mixing model revealed that the proportion of woody plant matter in fungus combs increased with increasing woody plant cover in the nest surroundings. Nitrogen content of fungus combs was positively correlated with woody plant cover around the mounds and negatively correlated with the proportion of grass matter in the comb. Considering the high N demand of large Macrotermes colonies, woody plant matter seems to thus represent a more profitable food source than grass. As grass is also utilized by grazing mammals, and the availability of grass matter typically fluctuates over the year, mixed woodland-grasslands and bushlands seem to represent more favorable habitats for large Macrotermes colonies than open grasslands.Peer reviewe

Small mammal tooth enamel carbon isotope record of C4 grasses in late Neogene China

Peer reviewe

Caste-specific nutritional differences define carbon and nitrogen fluxes within symbiotic food webs in African termite mounds

Fungus-growing termites of the genus Macrotermes cultivate symbiotic fungi (Termitomyces) in their underground nest chambers to degrade plant matter collected from the environment. Although the general mechanism of food processing is relatively well-known, it has remained unclear whether the termites get their nutrition primarily from the fungal mycelium or from plant tissues partly decomposed by the fungus. To elucidate the flows of carbon and nitrogen in the complicated food-chains within the nests of fungus-growing termites, we determined the stable isotope signatures of different materials sampled from four Macrotermes colonies in southern Kenya. Stable isotopes of carbon revealed that the termite queen and the young larvae are largely sustained by the fungal mycelium. Conversely, all adult workers and soldiers seem to feed predominantly on plant and/or fungus comb material, demonstrating that the fungal symbiont plays a different nutritional role for different termite castes. Nitrogen stable isotopes indicated additional differences between castes and revealed intriguing patterns in colony nitrogen cycling. Nitrogen is effectively recycled within the colonies, but also a presently unspecified nitrogen source, most likely symbiotic nitrogen-fixing bacteria, seems to contribute to nitrogen supply. Our results indicate that the gut microbiota of the termite queen might be largely responsible for the proposed nitrogen fixation.Peer reviewe

DIETS IN THREE LATE MEDIEVAL TO EARLY MODERN COASTAL POPULATIONS IN FINLAND ACCORDING TO THE δ13C AND δ15N VALUES OF ARCHAEOLOGICAL BONE AND DENTIN COLLAGEN

We explored the diets in three populations (Iin Hamina, Oulu, Rauma) dating between the late Middle Ages and mid-19th century. We compared diets of mid-childhood, adolescence, and adulthood based on the carbon and nitrogen stable isotope ratios in dentin (PM2, M3) and bone collagen. The δ13C values were typical of terrestrial C3 environments and to be expected by the brackish Baltic Sea. The 13C content in the water decreases north- wards, which was reflected in the results. The analyses displayed overall elevated δ15N values, which is consistent with fish having been an important part of the nutrition of all the populations. The PM2 and bone collagen δ15N values diverged in the Iin Hamina population, implying different diets of children and adults

Source of strontium in archaeological mobility studies-marine diet contribution to the isotopic composition

The strontium isotope composition of human tissues is widely used in archaeological mobility studies. However, little attention is paid to the relative contributions of terrestrial versus marine sources of strontium in these studies. There is some debate over the role of a solid diet versus drinking water as the most important source of strontium for the human body, with related possibilities of misinterpretation of the archaeological record if only strontium isotope compositions of the biosphere are studied. However, there is a third component, marine strontium, which is commonly not assumed to contribute towards the strontium isotope composition of archaeological skeletal remains, especially in locations that are not directly coastal. To illustrate the potentially obfuscating effects of mixed Sr sources in a human population, we present a case study of twelve individuals from the medieval Finnish site Iin Hamina with a known dietary history. Our study shows that marine consumption is a significant factor explaining the strontium isotope composition of the Iin Hamina human remains, with implication of erroneous conclusions about immigration without prior knowledge of diet composition. Thus, future studies should always incorporate a rigorous analysis of dietary history, with special regard to potential consumption of aquatic resources, when strontium isotope analysis is used as a method in the study of palaeomobility

Thriving or surviving? The isotopic record of the Wrangel Island woolly mammoth population

The world's last population of woolly mammoths (Mammuthus primigenius) lived on Wrangel Island persisting well into the Holocene, going extinct at ca. 4000 cal BP. According to the frequency of 'radiocarbon dated mammoth remains from the island, the extinction appears fairly abrupt. This study investigates the ecology of the Wrangel Island mammoth population by means of carbon, nitrogen and sulfur isotope analyses. We report new isotope data on 77 radiocarbon dated mammoth specimens from Wrangel Island and Siberia, and evaluate them in relation to previously published isotope data for Pleistocene mammoths from Beringia and lower latitude Eurasia, and the other insular Holocene mammoth population from St. Paul Island. Contrary to prior suggestions of gradual habitat deterioration, the nitrogen isotope values of the Wrangel Island mammoths do not support a decline in forage quality/quantity, and are in fact very similar to their north Beringian forebears right to the end. However, compared to Siberian mammoths, those from Wrangel Island show a difference in their energy economy as judged by the carbon isotope values of structural carbonate, possibly representing a lower need of adaptive strategies for survival in extreme cold. Increased mid-Holocene weathering of rock formations in the central mountains is suggested by sulfur isotope values. Scenarios related to water quality problems stemming from increased weathering, and a possibility of a catastrophic starvation event as a cause of, or contributing factor in their demise are discussed. (C) 2019 The Authors. Published by Elsevier Ltd.Peer reviewe

The dIANA database – Resource for isotopic paleodietary research in the Baltic Sea area

Paleodietary research is a complex field, which requires large sets of background information. Owing to increasing interest and activity in the field, a substantial amount of archaeological isotope baseline data exist for Northern Europe, consisting mainly of animal bone collagen δ13C, δ15N, and δ34S values. However, the data are scattered into dozens of publications written in multiple languages and less-accessible formats, making the data laborious to use. This article presents the first compilation work of this data, the open access dIANA database (Dietary Isotopic baseline for the Ancient North; https://www.oasisnorth.org/diana.html), aimed to support (paleo)dietary research in the Baltic Sea area. The database work is complemented with new analyses of archaeological and (pre-)modern domestic and wild fauna from Finland and Russia broadening the selection of analysed species in the database. We present and discuss data examples, which on one hand show existing spatiotemporal isotope patterns related to diet and differences in the environmental carbon sources and on the other, also visualize the current status of baseline research and the need for further analyses in the circum-Baltic area.Paleodietary research is a complex field, which requires large sets of background information. Owing to increasing interest and activity in the field, a substantial amount of archaeological isotope baseline data exist for Northern Europe, consisting mainly of animal bone collagen δ13C, δ15N, and δ34S values. However, the data are scattered into dozens of publications written in multiple languages and less-accessible formats, making the data laborious to use. This article presents the first compilation work of this data, the open access dIANA database (Dietary Isotopic baseline for the Ancient North; https://www.oasisnorth.org/diana.html), aimed to support (paleo)dietary research in the Baltic Sea area. The database work is complemented with new analyses of archaeological and (pre-)modern domestic and wild fauna from Finland and Russia broadening the selection of analysed species in the database. We present and discuss data examples, which on one hand show existing spatiotemporal isotope patterns related to diet and differences in the environmental carbon sources and on the other, also visualize the current status of baseline research and the need for further analyses in the circum-Baltic area.Peer reviewe