Elevated δ15N Values Research Articles

Mycorrhizal specialization toward each distinct Oliveonia fungus in two closely related photosynthetic Dactylostalix orchids

Abstract Although rhizoctonias from Ceratobasidiaceae, Tulasnellaceae and Serendipitaceae are typical orchid mycobionts, orchid mycorrhizal fungi exhibit vast taxonomic and ecological diversity. This diversity stems from the high specificity of orchid mycorrhizal associations and the remarkable diversity of over 28,000 orchid species. The subtribe Calypsoinae is particularly notable for its diverse mycorrhizal partnerships, including rhizoctonias, ectomycorrhizal and saprotrophic non‐rhizoctonia fungi. However, the mycobionts within certain Calypsoinae lineages, such as the genus Dactylostalix, remain understudied. This study explores the physiological ecology of two photosynthetic Calypsoinae species, Dactylostalix ringens and Dactylostalix uniflora, to gain insight into potentially novel associations and their ecological implications. We analysed the mycorrhizal communities of both Dactylostalix species using high‐throughput ITS metabarcoding of root samples collected from multiple locations. Additionally, we measured the natural abundances of 13C and 15N isotopes in the leaves of the two Dactylostalix species and their co‐occurring autotrophic reference plants, as well as in fungal pelotons isolated from D. ringens, to assess the potential for partial mycoheterotrophy. Our findings revealed that D. ringens and D. uniflora form specialized mycorrhizal associations predominantly with distinct lineages of Oliveonia (Oliveoniaceae, Auriculariales), even in sympatric populations. Stable isotope analysis showed that both Dactylostalix species exhibited conflicting isotopic signals: elevated δ15N values, supporting partial mycoheterotrophy, but lower δ13C values compared to autotrophic plants, suggesting autotrophy. Peloton samples from D. ringens displayed only modest 13C enrichment relative to autotrophic references. These conflicting isotopic signals make it difficult to precisely determine whether both Dactylostalix species are autotrophic or partially mycoheterotrophic. Intriguingly, the 13C and 15N signatures of Dactylostalix species and their pelotons resemble those of many rhizoctonia‐associated orchids. This isotopic evidence implies a niche overlap with endophytic tendencies between rhizoctonias and Oliveonia, suggesting that potential endophytic traits may have facilitated the recruitment of Oliveonia as novel mycorrhizal partners. Furthermore, the mycorrhizal segregation between D. ringens and D. uniflora likely promotes their sympatric coexistence and may contribute to reproductive isolation through ecological specialization. Read the free Plain Language Summary for this article on the Journal blog.

Depositing skeletal remains in Czech and Moravian ossuaries and associated climatic variations

AbstractSamples of the bones of 47 individuals from 46 Czech and Moravian ossuaries were dated by the 14C method and analyzed for the collagen isotopic composition of carbon (δ13C) and nitrogen (δ15N). Most of the data for the ages of the remains corresponded to the cooler and damper periods described over the past 1000 years. Of the studied samples, the greatest number of remains corresponded to the Spörer (1400–1570), Dalton (1790–1830) and Wolf minima (1280–1350). One sample studied falls within the Maunder minimum (1645–1715). It can be assumed that these minima are connected with a reduced production of food and fodder, that may have initiated famines, epidemics and armed conflicts. Individual climatic minima showed positive correlations between δ13C and δ15N values, indicating that the individuals studied consumed complementary plant or animal diets to different degrees. The elevated δ15N values in our studied samples compared to the skeletal compositions of the population of the La Tène period (380 – 150 BC) and Germanic inhabitants in the territory of Bohemia (5th–6th centuries AD) and Great Moravia (9th–early 10th centuries AD) might reflect the effect of greater consumption of animal proteins or the proteins of omnivorous animals and fish, which compensated for the lack of plant foodstuffs during the colder periods.The isotopic composition of carbon and nitrogen of the bone collagen for the Spörer and Dalton minima differs from the Wolf minimum. The younger minima show higher δ15N values for a given δ13C value.

Nitrogen isotopes in herbaria document historical nitrogen sewage pollution in the Mersey Estuary, England

A schematic figure illustrating how nitrogen isotopes (δ15N) from treated–raw sewage enters an estuary, is taken up by macroalgae (seaweed). Treated sewage produces more elevated δ15N values compared to raw sewage.

Symbiotic Relationship of Comasterschlegelii (Crinoidea: Comatulidae) and Gymnolophus obscura (Ophiuroidea: Ophiotrichidae) Derived from Stable Isotope and Fatty Acid Analyses.

Coral reef community exhibits high species diversity and a broad range of biological relationships, including widespread symbiosis and complex food utilization patterns. In our study, we investigated the symbiotic relationship between the commonly crinoid host Comaster schlegelii and its ophiuroid obligatory symbiont Gymnolophus obscura. Using a combination of fatty acid biomarkers and stable isotopic compositions, we explored differences in their organic matter utilization strategies and nutritional relationships. The result of stable isotopes revealed that G. obscura had higher δ15N values than its crinoid host. Particulate organic matter and phytoplankton were identified as the primary food sources for both species, however C. schlegelii showed a higher proportional contribution from benthic microalgae. Fatty acid markers showed that C. schlegelii was more dependent on benthic microalgae such as diatoms, and less on debritic organic matter and bacteria than G. obscura. Elevated δ15N values of G. obscura and similar food source contribution rates between the host and symbiont suggest that ophiuroid feeds on materials filtered by crinoids and have similar diet to the host. Our results provide insights into the symbiotic patterns of crinoids and ophiuroids, while also supplying foundational data on how symbiotic reef species select organic matter utilization strategies to adapt to their environment.

Diffuse and concentrated nitrogen sewage pollution in island environments with differing treatment systems

Macroalgae is an under-utilised tool as a bioindicator of anthropogenic nitrogen loading to the coastal environment in the UK. This study compared two island systems—Jersey (Channel Islands) and St Mary’s (Isles of Scilly) to assess how differing sewerage infrastructure affects nitrogen loading. A total of 831 macroalgae samples of Fucus vesiculosus and Ulva sp. were analysed for nitrogen isotopes (δ15N). Elevated δ15N values were recorded for Jersey (> 9‰) in St Aubin’s Bay—caused by the outflow of the Bellozanne Sewerage Treatment Works (STW). δ15N isoplots maps indicate low diffusion of nitrogen out of St Aubin’s Bay. St Mary’s produced a varied δ15N isoplot map in comparison. δ15N was typically lower and is attributed to a smaller population and inefficient STW. Outflow of sewage/effluent at Morning Point, Hugh Town and Old Town produced elevated δ15N values in comparison to the island average. St Mary’s inefficient sewerage treatment and reliance on septic tanks/soakaways complicates δ15N interpretation although it still indicates that nitrogen pollution is an island-wide issue. Future sewerage development and upgrades on islands are required to prevent similar effluent environmental issues as recorded in St Aubin’s Bay. This study advocates the use of macroalgae as a bioindicator of nitrogen effluent in the marine environment.

Body size, depth of occurrence, and local oceanography shape trophic structure in a diverse deep-pelagic micronekton assemblage

The Gulf of Mexico’s (GOM) deep-pelagic realm is one of the planet’s most speciose pelagic ecoregions, but detailed knowledge of ecosystem structure and function is lacking. Understanding trophic structure is critical to understanding ecosystem dynamics as trophic interactions regulate the flow of energy through ecosystems and influence the resilience of ecosystems to disturbance. Using novel stable isotope (SIA) data and historical stomach content (SCA) data, we examined deep-pelagic trophic structure using 58 species of micronekton from the GOM that encompassed a variety of migratory behaviors, depth distributions, and trophic strategies. We identified major trophic groupings, explored the extent that differences in diet, body size, vertical migration, and presence of a mesoscale feature (Loop Current) explained micronekton isotopic variation and estimated species-specific trophic positions. Cluster analysis of SIA data identified four trophic groups, although species were not strictly clustered by diet. Specifically, non-migratory zooplanktivores with elevated δ15N values were grouped with vertically migrating piscivores, suggesting some non-migratory species could be feeding within food chains with elevated isotopic baselines. The mean δ13C values of species encompassed a narrow range from −21.6 ‰ to −18.1 ‰, with variation in δ13C values of vertically migrating species explained by a positive relationship with body size and higher δ13C values in Loop Current water. In contrast, variation in δ13C values of non-migrators was primarily explained by elevated values in deeper-dwelling species and in larger species. The mean δ15N values of species ranged between 5.0 ‰ and 11.5 ‰, with variation in δ15N values of vertical migrators explained by a positive relationship with body size and lower δ15N values in Loop Current water. Variation in the δ15N values of non-migrators was largely explained by elevated δ15N values in deeper-dwelling species and in larger-bodied species. Trophic position (TP) estimations for the assemblage ranged between 2.6 and 4.9. The elevated δ15N values in non-migratory species led to higher TP estimates relative to estimates derived from stomach content data, but agreement between TP estimates using SIA and SCA was high for vertically migrating taxa. This discrepancy may be a factor of vertical migrating species having a more similar feeding depth than non-migrators. Our results provide important insight into the trophic organization of low-latitude oligotrophic ecosystems and demonstrate that trophic variation within micronekton assemblages is primarily driven by differences in body size, location in the water column and position relative to salient oceanographic features.

Multiple nutritional strategies of hydrothermal vent shrimp (Rimicaris hybisae) assemblages at the Mid-Cayman Rise

Alvinocaridid shrimp occurring in dense assemblages close to vigorously venting orifices are characteristic of many vent fields on the Mid-Atlantic Ridge, Central Indian Ridge, and Mid-Cayman Rise. Episymbiotic bacteria of these shrimp are exposed to vent fluids enriched in inorganic nutrients (carbon dioxide, sulfide) that, together with dissolved oxygen in the surrounding seawater, sustain autotrophic growth and supply nourishment to the shrimp. Enigmatically, conspecific shrimp may also be found sparsely distributed in the periphery of a vent field, where there is little visual evidence of vent fluid flux. We tested the null hypothesis that nourishment sources were identical for the central (dense) and peripheral shrimp assemblages, using gut content and stable isotope analyses. Rimicaris hybisae were sampled from central and peripheral assemblages at the Von Damm Vent Field (Mid-Cayman Rise). Guts of centrally aggregated shrimp contained a white material inferred to be bacteria, while peripheral individuals contained this white material and/or pieces of crustacean exoskeletons. C, N, and S isotopic compositions of shrimp muscle tissues were significantly different between central and peripheral shrimp assemblages, and little overlap in isotopic space was found. A comparison of δ13C and δ34S values of gut contents and abdominal tissues revealed that abdominal tissue composition reflects the shrimp's source of nourishment. Slight but significantly elevated δ15N values in peripheral shrimp, together with crustacean exoskeleton fragments in the gut, suggest facultative carnivory in peripherally aggregated shrimp. The lower δ13C and δ34S values in individuals from the peripheral assemblages are also consistent with a mixotrophic diet. We conclude that central and peripheral assemblages of R. hybisae have different nourishment sources, with central assemblages relying on episymbionts, while peripheral assemblages have diverse nourishment sources comprising bacteria and Crustacea.

Stable carbon and nitrogen isotopes identify nuanced dietary changes from the Bronze and Iron Ages on the Great Hungarian Plain

The Great Hungarian Plain (GHP) served as a geographic funnel for population mobility throughout prehistory. Genomic and isotopic research demonstrates non-linear genetic turnover and technological shifts between the Copper and Iron Ages of the GHP, which influenced the dietary strategies of numerous cultures that intermixed and overlapped through time. Given the complexities of these prehistoric cultural and demographic processes, this study aims to identify and elucidate diachronic and culture-specific dietary signatures. We report on stable carbon and nitrogen isotope ratios from 74 individuals from nineteen sites in the GHP dating to a ~ 3000-year time span between the Early Bronze and Early Iron Ages. The samples broadly indicate a terrestrial C3 diet with nuanced differences amongst populations and through time, suggesting exogenous influences that manifested in subsistence strategies. Slightly elevated δ15N values for Bronze Age samples imply higher reliance on protein than in the Iron Age. Interestingly, the Füzesabony have carbon values typical of C4 vegetation indicating millet consumption, or that of a grain with comparable δ13C ratios, which corroborates evidence from outside the GHP for its early cultivation during the Middle Bronze Age. Finally, our results also suggest locally diverse subsistence economies for GHP Scythians.

Stable isotopes reveal seasonal dietary responses to agroforestry in a venomous mammal, the Hispaniolan solenodon (Solenodon paradoxus).

While trends in tropical deforestation are alarming, conservation biologists are increasingly recognizing the potential for species survival in human‐modified landscapes. Identifying the factors underlying such persistence, however, requires basic ecological knowledge of a species’ resource use. Here, we generate such data to guide conservation of an understudied venomous mammal, the Hispaniolan solenodon (Solenodon paradoxus), that occupies a mosaic landscape of agriculture and forest fragments in the western Dominican Republic. Using feces collected in both wet and dry seasons, we found significant differences in the stable isotope values of carbon (δ13C) between pasture (−24.63 ± 2.31‰, Las Mercedes) and agroforestry (−28.07 ± 2.10‰, Mencia). Solenodon populations in agricultural areas occupied wider isotopic niche spaces, which may be explained by more diverse resource within these patches or individuals combining resources across habitats. We detected elevated δ15N values in the dry season of pasture areas (8.22 ± 2.30‰) as compared to the wet season (5.26 ± 2.44‰) and overall narrower isotopic niche widths in the dry season, suggestive of the impacts of aridity on foraging behavior. Our work highlights the importance of considering a more nuanced view of variations in ‘modified’ or “agricultural” landscapes as compared with strictly protected national parks. We suggest that seasonal differences in foraging should be considered as they intersect with landscape modification by landowners for maintaining resources for focal consumers. This work adds to a growing body of literature highlighting that fecal stable isotopes are a non‐invasive and cost‐effective monitoring tool that is particularly well‐suited for cryptic small mammal species, ensuring actionable and evidenced‐based conservation practices in the tropic's rapidly changing landscapes.

Diet and urbanisation in medieval Holland. Studying dietary change through carious lesions and stable isotope analysis

AbstractIn the late medieval period, Holland experienced substantial socio‐economic change. While the region was largely undeveloped prior to 1200 CE, the period after was characterised by extensive urbanisation and flourishing international trade, changes that would have impacted many aspects of life. This paper investigates the effect of these changes on diet by comparing skeletal collections from the early/central medieval rural village of Blokhuizen (800–1200 CE) to the late medieval urban town of Alkmaar (1448–1572 CE) using a combination of the prevalence and location of carious lesions (nteeth = 3475) and stable carbon and nitrogen isotope data (n = 50). Results show that the urban Alkmaar population had a significantly higher caries frequency (7.4% vs. 16.1%), starting at a younger age. Moreover, Alkmaar had significantly more approximal caries. These results point to increased consumption of cariogenic products, such as sugars and starches, by the urban citizens. Dietary differences are also demonstrated by the stable isotope data. Alkmaar individuals have significantly enrichedδ15N ratios and more variableδ13C ratios compared with rural Blokhuizen. The elevatedδ15N values may be due to increased consumption of fish or animals such as omnivorous pigs and chickens. The combination of caries and isotopic data points to clear changes in diet suggesting that urban individuals in the late medieval period had a substantially different diet compared with early rural inhabitants from the same area. Specifically, an increase in market dependence, availability of international trade products, and the growth of commercial fishing in the late medieval period may have contributed to this dietary shift. Future research should include a late medieval rural population to better understand the effects of late medieval socio‐economic developments outside of the urban environment. This study demonstrates that the integration of palaeopathology and stable isotopic research provides a more complete understanding of dietary changes in medieval Holland.

Leprosy in medieval Denmark: Exploring life histories through a multi-tissue and multi-isotopic approach.

By focusing on two Danish leprosaria (Naestved and Odense; 13th-16th c. CE) and using diet and origin as proxies, we follow a multi-isotopic approach to reconstruct life histories of patients and investigate how leprosy affected both institutionalized individuals and the medieval Danish community as a whole. We combine archaeology, historical sources, biological anthropology, isotopic analyses (δ13 C, δ15 N, δ34 S, 87 Sr/86 Sr) and radiocarbon dating, and further analyze bones with different turnover rates (ribs and long bones). The δ13 C, δ15 N and δ34 S results indicate a C3 terrestrial diet with small contributions of marine protein for leprosy patients and individuals from other medieval Danish sites. A similar diet is seen through time, between males and females, and patients with and without changes on facial bones. The isotopic comparison between ribs and long bones reveals no significant dietary change. The δ34 S and 87 Sr/86 Sr results suggest that patients were local to the regions of the leprosaria. Moreover, the radiocarbon dates show a mere 50% agreement with the arm position dating method used in Denmark. A local origin for the leprosy patients is in line with historical evidence, unlike the small dietary contribution of marine protein. Although only 10% of the analyzed individuals have rib/long bone offsets that undoubtedly show a dietary shift, the data appear to reveal a pattern for 25 individuals (out of 50), with elevated δ13 C and/or δ15 N values in the ribs compared to the long bones, which points toward a communal type of diet and reveals organizational aspects of the institution.

Stable isotopes demonstrate the importance of freshwater fisheries in Late Holocene native Californian diets in the California Delta

Estimating paleodiet from macroscopic faunal and floral remains alone is difficult. Taphonomic biases make direct quantitative comparisons of different categories, such as fish bone, ungulate bone, and charred seeds challenging. Stable isotope data can help in this regard. To highlight this process, we present new bone collagen stable isotope data (δ13C, δ15N, and δ34S) from a series of animal and human remains from a Late Holocene (ca. 1000–300 cal BP) archaeological site in the California Delta. We contrast stable isotope data from humans with that from canid (Canis sp.), deer (Odocoileus sp.), elk (Cervus sp.), pronghorn (Antilocapra americana), and Sacramento perch (Archoplites interruptus) remains from the site. Most of these species are endangered or extirpated locally, making archaeological sites a primary source of paleoecological data. Of fourteen human individuals, twelve show isotope values consistent with heavy exploitation of freshwater wetland resources, which we interpret as a “local” dietary signature. By contrast, two individuals display a pattern more similar to precontact humans in other parts of interior California, which we interpret as recent immigrants to the site. Three subadults display elevated δ15N values relative to adults, consistent with these individuals still consuming significant amounts of breast milk near the time of death. A linear mixing model provides a quantitative estimate the role of different food groups in local diets. Together, we estimate that local adults gained over 60% of their protein from freshwater fishes. This heavy reliance on local fisheries is consistent with large numbers of fish bone from the site.

Sea cage aquaculture may provide an energetic subsidy to wild juvenile cod in coastal bays of southern Newfoundland, Canada

Sea cage aquaculture can alter the spatial distribution of wild fish populations; however, little is known about the dietary habits of wild fish frequenting sea cages. We used wild juvenile cod Gadus morhua reared in the laboratory and fed either an aquafeed pellet or marine-based diet to determine trophic discrimination factors (TDFs) of stable carbon (δ13C) and nitrogen (δ15N) isotope values in white muscle tissue and baseline liver proportions of vegetable-oil based (VOB) fatty acids. We then used δ13C and δ15N and proportions of VOB fatty acids to investigate the dietary habits of wild cage-associated juvenile and adult Atlantic cod and adult Atlantic redfish Sebastes fasciatus. Cod and redfish were collected in the immediate area of sea cages and reference areas of no aquaculture production. Juvenile cod captured around sea cages had both elevated δ13C and δ15N values and proportions of VOB fatty acids, and isotopic fractionation comparable to laboratory cod fed an aquafeed diet. However, differences in δ13C and δ15N and proportions of VOB fatty acids between cage-associated and reference site adult cod and redfish were predominately absent. Results suggest that sea cages may provide an energetic subsidy to juvenile cod but perhaps not at the level to sustain adult cod or redfish. Therefore, the lack of differences suggests that both adult groups may be using cage sites opportunistically and only for short duration, as isotopic values and fatty acid proportions were not consistent with waste feed consumption despite individuals being collected in close proximity to sea cages.

Trophic Structure and Sources of Variation Influencing the Stable Isotope Signatures of Meso- and Bathypelagic Micronekton Fishes

To better understand spatiotemporal variation in the trophic structure of deep-pelagic species, we examined the isotope values of particulate organic matter (POM) (isotopic baseline) and seven deep-pelagic fishes with similar diet compositions but contrasting vertical distributions across mesoscale features in the Gulf of Mexico (GOM) using stable isotope and amino acid compound-specific isotope analyses. Species examined included four migratory (Benthosema suborbitale, Lepidophanes guentheri, Melamphaes simus, Sigmops elongatus) and three non-migratory zooplanktivorous fishes (Argyropelecus hemigymnus, Cyclothone obscura, Sternoptyx pseudobscura). Isotopic values of POM increased with depth, with meso- and bathypelagic samples characterized by higher δ13C and δ15N values relative to epipelagic samples. Despite similar diet compositions, mean δ15N values of fishes spanned 3.43‰ resulting in mean trophic position estimates among species varying by 1.09 trophic levels. Interspecific differences in δ15N were driven by higher δ15N values in the non-migratory and deepest dwelling C. obscura (10.61‰) and lower δ15N values in the migratory and shallowest dwelling L. guentheri (7.18‰) and B. suborbitale (8.11‰). Similarly, fish δ15NsourceAA values were correlated with depth, with values found to be lowest in the migratory L. guentheri and B. suborbitale and highest in the non-migratory C. obscura. Our data suggests that depth-related trends in fish δ15N and δ15NsourceAA values are driven by shallower dwelling species feeding within epipelagic food webs supported by POM with lower δ15N values, while deeper dwelling, non-migratory species increasingly use food webs at depth supported by POM with elevated δ15N values. Horizontal isotopic variation was observed across a large mesoscale oceanographic feature (Loop Current) for POM and migratory and non-migratory species which were characterized by higher δ13C and lower δ15N values in the anticyclonic Loop Current relative to surrounding water masses. Our results demonstrate that isotopic values of POM can vary significantly over relatively small horizontal and vertical scales, and that baseline variation can be conserved in the signatures of higher-order consumers. By gaining a more thorough understanding of the sources contributing to isotopic variation of deep-pelagic fishes, this paper will inform the design and interpretation of future feeding studies in the pelagic realm and advances our knowledge of deep-pelagic food web structure.

Disentangling the multiple effects of stream drying and riparian canopy cover on the trophic ecology of a highly threatened fish

Abstract Understanding risks to aquatic systems posed by changing drought regimes is particularly important for the conservation of already threatened taxa. However, little is known about how local environmental conditions, especially those in heavily human‐influenced situations, interact with regional shifts such as droughts to alter realised impacts on aquatic communities, including threatened top predators. Here, we investigated the combined effects of stream drying intensity and riparian canopy cover on the trophic interactions of critically endangered kōwaro, or Canterbury mudfish (Neochanna burrowsius) in an agricultural area of New Zealand. Fish populations and their potential prey, both terrestrial and aquatic, as well as environmental variables, including riparian canopy cover and drying measured with stage loggers, were sampled over eight visits to 24 sites spanning orthogonal drying and canopy gradients. Stable isotope ratios, 13C/12C and 15N/14N, were used to investigate trophic links between mudfish and their terrestrial and aquatic prey across these gradients. When non‐native willows (predominantly Salix fragilis) dominated the riparian canopy, increased tree cover led to elevated drying intensity, probably driven by their relatively high water demands compared to other trees. However, in the absence of willows, canopy cover had no effect on drying intensity. Although this was the only direct link between these two environmental factors, they had opposing effects on kōwaro populations, which will be important for management under drought. Increased drying intensity contributed to elevated abundance of microcrustacea and aquatic Diptera larvae, and an increase in the relative abundance of kōwaro juveniles. However, drying‐affected kōwaro populations also had fewer large reproductive adults and elevated δ15N values, probably driven by physiological limitations and an increase in kōwaro cannibalism, respectively. By comparison, increased canopy cover enhanced input of terrestrial invertebrates, a food resource for larger kōwaro, leading to elevated kōwaro δ13C values, no effects on δ15N values, and higher relative abundance of large kōwaro in shaded streams compared to unshaded streams. Thus, the riparian canopy cover was able to offset some of the effects of drying. Overall, we found no interactions between drying intensity and canopy cover affecting kōwaro. However, their opposing effect highlights the important role local conditions such as riparian canopies play on aquatic communities and their potential role as a restoration tool to mitigate the effects of large‐scale shifts such as drought.

Diet patterns in medieval to early modern (14th-early 20th c.) coastal communities in Lithuania.

Coastal residents are quite often expected to consume a significant amount of aquatic resources, though historical evidence often reveals a rather complex diet. To better understand the actual consumption and the distribution of various foods, stable isotope (δ13C and δ15N) analyses were employed to skeletal remains from three coastal communities, Palanga, Kretinga and Smeltė, ranging in date from the medieval period to the early modern ages (14th-early 20th c.) near the Curonian Lagoon and the Baltic Sea in Lithuania. Animal bones from the region, covering the same time periods, were also analysed. Stable isotope results were compared with historical records. According to historical sources different types of diet were prevalent during that period of time: Medieval Prussian-Lithuanian peasant, Lithuanian fisherman, German urban, and religious-based. Elevated δ15N values for Smeltė samples suggest a diet consisting of considerable amounts of freshwater fish protein, which is in contrast to historical sources. There were no significant differences in stable isotope values between males and females, while subadult δ15N values were significantly higher than adult ones, indicating that those children were breastfed for an extended period. Meanwhile, Palanga and Kretinga samples had isotope values suggesting a high reliance on terrestrial resources and a peasant type of diet.

HUMAN DIETARY COMPLEXITY IN TIANSHAN REGION AND THE INFLUENCE OF CLIMATE ON HUMAN PALEODIET

ABSTRACTWith the popularization of carbon and nitrogen stable-isotope analysis methods used on archaeological samples from Xinjiang, the ancient paleodiet there has been revealed. However, research about isotopic analysis combined with environmental factors is rare, especially in such a variable and complex climate as that of the Tianshan region. We systematically analyzed the δ13C and δ15N results from animals and humans for dietary reconstruction of nomadic pastoralists from the Tianshan region during 3900–1200 cal BP. The δ13C and δ15N values for animals (sheep/goat, horse and cattle; n = 57) have a wide range from –20.8‰ to –14.7‰ for δ13C (–19.2 ± 1.0‰) and 3.2‰ to 9.9‰ for δ15N (7.0 ± 1.2‰). The δ13C and δ15N values from humans range from –19.6 to –12.3‰ (–16.0 ± 1.5‰) and 7.1 to 16.7‰ (–13.6 ± 1.5‰), respectively. The animal δ15N results indicate that the dry environment in the Tianshan region may result in elevated δ15N values. Synthesizing animal and human isotope results suggests that the inhabitants engaged in mobile herding economies subsidized with crops and wild animal meat from the Tianshan Mountains. In conclusion, we found that the regional environment closely relates to crop types, and temporal climate change has an effect on human dietary structure. Therefore, climate condition cannot be ignored when studying human paleodiet.

Isotopic niche differs between seal and fish-eating killer whales (Orcinus orca) in northern Norway.

Ecological diversity has been reported for killer whales (Orcinus orca) throughout the North Atlantic but patterns of prey specialization have remained poorly understood. We quantify interindividual dietary variations in killer whales (n = 38) sampled throughout the year in 2017–2018 in northern Norway using stable isotopic nitrogen (δ15N: 15N/14N) and carbon (δ13C: 13C/12C) ratios. A Gaussian mixture model assigned sampled individuals to three differentiated clusters, characterized by disparate nonoverlapping isotopic niches, that were consistent with predatory field observations: seal‐eaters, herring‐eaters, and lumpfish‐eaters. Seal‐eaters showed higher δ15N values (mean ± SD: 12.6 ± 0.3‰, range = 12.3–13.2‰, n = 10) compared to herring‐eaters (mean ± SD: 11.7 ± 0.2‰, range = 11.4–11.9‰, n = 19) and lumpfish‐eaters (mean ± SD: 11.6 ± 0.2‰, range = 11.3–11.9, n = 9). Elevated δ15N values for seal‐eaters, regardless of sampling season, confirmed feeding at high trophic levels throughout the year. However, a wide isotopic niche and low measured δ15N values in the seal‐eaters, compared to that of whales that would eat solely seals (δN‐measured = 12.6 vs. δN‐expected = 15.5), indicated a diverse diet that includes both fish and mammal prey. A narrow niche for killer whales sampled at herring and lumpfish seasonal grounds supported seasonal prey specialization reflective of local peaks in prey abundance for the two fish‐eating groups. Our results, thus, show differences in prey specialization within this killer whale population in Norway and that the episodic observations of killer whales feeding on prey other than fish are a consistent behavior, as reflected in different isotopic niches between seal and fish‐eating individuals.

Babes, bones, and isotopes: A stable isotope investigation on nonadults from Aventicum, Roman Switzerland (first–third century CE)

AbstractThe study of infant feeding practices in archaeological populations can aid in the understanding of cultural attitudes towards dietary choices and how specific circumstances experienced by mothers and their offspring influence childhood health and survivorship. Breastfeeding and weaning patterns have received increased interest in Roman bioarchaeology, especially through the application of stable isotopic investigation of nitrogen (δ15N) and carbon (δ13C) values. This study presents the stable isotopic results of the first Roman bone sample analysed from Switzerland (30 nonadults and nine females), allowing us an unprecedented insight into health and diet at the site of Aventicum/Avenches, the capital city of the territory of Helvetii in Roman times (first–third century AD). The fact that the majority of the nonadult samples subject to stable isotope analysis were perinates highlights the complex relationship between their δ15N and δ13C values and those of adult females, as different factors, including variation of fetal and maternal stable isotope values, the possible effects of intrauterine growth, and maternal/fetal disease and/or nutritional stress (e.g., nutritional deficiencies such as scurvy, parasitic infections, such as malaria), could have influenced the observed elevated δ15N values.

A new method for investigating the relationship between diet and mortality: hazard analysis using dietary isotopes

Background: The population of Roman Britain are renowned for having elevated nitrogen (δ15) stable isotope values, which have been interpreted as evidence for the increased consumption of marine products. However, such results are now understood to also reflect episodes of stress and disease, suggesting that new interpretations are warranted.Aim: To test a novel approach which combines hazard mortality analysis and stable isotope data to determine whether there is a relationship between age-at-death, elevated δ15N values and mortality risk.Subjects and methods: This study used published osteological and dietary stable isotope data for nitrogen (δ15N) and carbon (δ13C) of 659 1st–5th century AD individuals aged >12 years old excavated from Roman cemeteries in Britain. The relationship between diet and mortality risk was assessed using the Gompertz hazard model, and differences in median reported isotope values between the sexes was determined using a Mann Whitney test.Results: It was discovered that higher δ15N levels are associated with elevated risks of mortality, whereas the opposite pattern was observed for δ13C, and males had higher median δ13C and δ15N values.Conclusion: This study successfully demonstrated that stable isotope data can be integrated into hazard models, allowing one to connect diet and mortality in past populations. It supports the findings of other isotope studies which have established that individuals with childhood stress/trauma will have different isotope patterns.