Differences In Stable Isotope Ratios Research Articles

Reconstructing diet after the fall of the Wari Empire in the central Andean Highlands: A study of human dental calculus

Stable isotopes from bones and teeth have been used to reconstruct human lifeways in bioarchaeological research for over 30 years. Recently, there have been efforts to use less invasive methods of analysis that meet ethical standards and do not compromise the integrity of human skeletal remains. To that end, this study examines dental calculus from human teeth as a proxy for paleodietary reconstruction. This current work builds on a handful of studies that have tested the use of dental calculus for reconstructing diet, which have shown mixed results. This study contributes to those ongoing efforts to improve methods and capacities in paleodiet research. The sample is comprised of dental calculus from individuals from the Wari (600–1000 CE) and post-Wari periods (1000–1400 CE). Individuals from both time periods with stable carbon and nitrogen isotope data from the calculus are directly compared to the stable isotope results from human bone collagen, dental carbonates, and bone carbonates. Results from dental calculus show δ13C that range from -20.5 ‰ to −12.3 ‰, consistent with the use of C4 plants (maize) as a major component of the diet. The δ13C from calculus are isotopically lighter and more varied than those obtained from collagen, and this is likely explained by the distinct composition of calculus compared to that of bone collagen and apatite. The δ15N from calculus range from +8.9 ‰ to +18.8 ‰, which is heavier than expected for highland maize-based diets in the Peruvian Andes. This may be explained by 15N enrichment from aridity or crop fertilization (e.g., camelid dung), especially during the post Wari period, a time of social upheaval and severe drought. The differences in stable isotope values may also be partially explained by the diet-sourced isotopes in bone collagen (e.g., averaging the last 5–10 years of life) versus that of dental calculus (e.g., averaging the last few years of life). Documenting these differences in stable isotope ratios from distinct components may aid in richer understandings of past diets and provide additional ways to compare diet through time and space. Indeed, as more researchers begin analyzing the stable isotope ratios from dental calculus, we can minimize destructive techniques and make direct comparisons between studies that use dental calculus. We suggest that this is an important expansion of our analytical toolkit.

Microecological characteristics of water bodies/sediments and microbial remediation strategies after 50 years of pollution exposure in ammunition destruction sites in China

The effects of long-term ammunition pollution on microecological characteristics were analyzed to formulate microbial remediation strategies. Specifically, the response of enzyme systems, N/O stable isotopes, ion networks, and microbial community structure/function levels were analyzed in long-term (50 years) ammunition-contaminated water/sediments from a contamination site, and a compound bacterial agent capable of efficiently degrading trinitrotoluene (TNT) while tolerating many heavy metals was selected to remediate the ammunition-contaminated soil. The basic physical and chemical properties of the water/sediment (pH (up: 0.57–0.64), nitrate (up: 1.31–4.28 times), nitrite (up: 1.51–5.03 times), and ammonium (up: 7.06–70.93 times)) were changed significantly, and the significant differences in stable isotope ratios of N and O (nitrate nitrogen) confirmed the degradability of TNT by indigenous microorganisms exposed to long-term pollution. Heavy metals, such as Pb, Zn, Cu, Cd, Cs, and Sb, have synergistic toxic effects in ammunition-contaminated sites, and significantly decreased the microbial diversity and richness in the core pollution area. However, long-term exposure in the edge pollution area induced microorganisms to use TNT as a carbon and nitrogen sources for life activities and growth and development. The Bacteroidales microbial group was significantly inhibited by ammunition contamination, whereas microorganisms such as Proteobacteria, Acidobacteriota, and Comamonadaceae gradually adapted to this environmental stress by regulating their development and stress responses. Ammunition pollution significantly affected DNA replication and gene regulation in the microecological genetic networks and increased the risk to human health. Mg and K were significantly involved in the internal mechanism of microbial transport, enrichment, and metabolism of TNT. Nine strains of TNT-utilizing microbes were screened for efficient TNT degradation and tolerance to typical heavy metals (copper, zinc and lead) found in contaminated sites, and a compound bacterial agent prepared for effective repair of ammunition-contaminated soil significantly improved the soil ecological environment.

Geographical traceability of gelatin in China using stable isotope ratio analysis.

Geographical traceability is crucial to the quality and safety control of gelatin. However, currently, methods for gelatin traceability have not been established anywhere in the world. This study aimed to investigate the possibility of differentiating the geographical origins of gelatin from different regions in China using stable isotope technology. To achieve this objective, 47 bovine stick bone samples from three different regions (Inner Mongolia, Shandong, and Guangxi, respectively) in China were collected, and gelatin was extracted from these bones using the enzymatic method. The fingerprint characteristics of stable isotopes of δ13C, δ15N, and δ2H of gelatin from different regions in China were studied. Moreover, isotopic changes from the bone to gelatin during the processing were examined to evaluate the effectiveness of these factors as origin indicators. The results of the one-way analysis of variance (ANOVA) showed that the δ13C, δ15N, and δ2H of gelatin from different regions display significant differences, and using the linear discriminant analysis (LDA), the correct differentiation of origin reached 97.9%. Certain differences in stable isotope ratios were observed during the processing of bone to gelatin samples. Nonetheless, the fractionation effect caused by the processing of bone to gelatin samples was not sufficient to influence the identification of gelatin from different origins, which proves that δ13C, δ15N, and δ2H are effective origin indicators of gelatin. In conclusion, the stable isotope ratio analysis combined with the chemometric analysis can be used as a reliable tool for identifying gelatin traceability.

Geographical differences in stable isotope ratios and fatty acid and lipid signatures of chub mackerel, Scomber japonicus, in waters around Japan

We analyzed stable isotope ratios, fatty acid, and lipid components of chub mackerel, Scomber japonicus, to evaluate their applicability as chemical biomarkers. Chub mackerel were collected in the East China Sea, the Sea of Japan, and the Pacific Ocean, with body sizes ranging from 51 to 388 mm. The total fatty acid and lipid contents (mg g–1) increased with growth, and the percent composition of fatty acids and lipids changed drastically. The percentages of docosahexaenoic acid (%DHA), stearic acid (%Ste), and arachidonic acid (%ARA) decreased and the percentage of oleic acid (%Ole) increased when the body length (fork length, FL) was about 250 mm. The amounts of triacylglycerols (TAG) in fish in the East China Sea were lower than in the Sea of Japan and Pacific Ocean. The percentage of TAG drastically increased at around 250 mm FL, however, the phosphatidylcholines (PC) drastically decreased. The ontogenetic differences in the fatty acid and lipid composition might be influenced by metabolic events such as growth and reproduction. The geographical differences in chub mackerel can be distinguished by using stable isotope ratios, the ω3:ω6 fatty acid and DHA:EPA (eicosapentaenoic acid) ratios, and six main fatty acids. These chemical biomarkers could be available for understanding habitat and migration of chub mackerel.

A Case Study to Establish a Basis for Evaluating Geographic Origin Claims of Timber From the Solomon Islands Using Stable Isotope Ratio Analysis

Global demand for low-cost forest products is leading manufacturers and traders to source timber and wood products from vulnerable nations and delicate ecosystems. One small island nation, the Solomon Islands, is seeing exploitation of natural resources accelerating to such a point that its natural forests may be exhausted by 2036. The main causes of natural forest loss on the archipelago are unsustainable or illegal logging practices. Various laws in consumer countries require that members of industry ensure that only legally sourced timber is placed onto their respective national markets. Those that break these laws or fail to act in a way that is compliant may be subject to harsh penalties. This study aims to establish scientific data to evaluate claims that timber has originated from the Solomon Islands. This will enable Operators to carry out due diligence analysis and permit members of Law Enforcement to conduct forensic investigations. Eighty timber core samples comprising 13 different genera of tropical trees were obtained from mature trees in two sites in the Solomon Islands (Guadalcanal and Kolombangara islands) during the period August 2019 to November 2019 using a Pickering Punch sampling device. Homogenised core samples were subject to δ18O, δ2H, δ13C, and δ34S stable isotope analysis using elemental analysis-isotope ratio mass spectrometry. Additional stable isotope data from relevant taxa and geographic origins (elevation, geographic co-ordinates) were also included in this research as an initial assessment of differences in stable isotope ratios between countries. Results show that significant differences are evident in the stable isotope ratios of the sampled taxa within the Solomon Islands (Guadalcanal and Kolombangara Islands) and between other countries. These data can be used as a basis of evaluation to evaluate origin claims of timber or wood products from the Solomon Islands, particularly Kolombangara Island. Furthermore, in the right context, these data can also be used to establish whether timber or wood products declared to be from origins other than the Solomon Islands have stable isotope ratios that are consistent with data from the Solomon Islands. If not, this would suggest foreign timber/forest products are from elsewhere and are being passed-off as originating from the Solomon Islands.

A piece of the puzzle: analyses of recent strandings and historical records reveal new genetic and ecological insights on New Zealand sperm whales

Cetacean strandings provide important opportunities to extend current knowledge on species or populations, particularly for species that are notoriously difficult to study, such as sperm whales Physeter macrocephalus (parāoa). Between 25 May and 9 June 2018, 13 male sperm whales stranded in Taranaki, New Zealand (NZ), with an additional male stranding 1 mo later in Clifford Bay, Marlborough. We profiled these 14 males for mitochondrial DNA (mtDNA) and carbon and nitrogen stable isotopes to examine their similarity to sperm whales from other geographic areas. Analyses of mtDNA revealed 7 haplotypes, including 1 not previously described (‘New’), and an additional haplotype (‘M’) new to NZ that had been previously reported in sperm whales of the Pacific region. Analysis of rare haplotypes found in NZ males suggested genetic links within NZ and the Southwest Pacific. Differences in stable isotope ratios indicated that, despite the close temporal proximity of these stranding events, individuals originated from at least 2 separate groups, with the whale stranded in Clifford Bay identified as being a regular visitor to Kaikōura, South Island. The analysis of stranding records in NZ dating back to 1873 indicated an increase in recorded single strandings since 1970, and a peak in single strandings in the austral summer months, but no seasonality for mass strandings. Sex predicted latitudinal location for single strandings, with 95.1% of female strandings occurring north of 42° S, fitting the general global distribution of female sperm whales limited to lower latitudes. This study provides the first temporal and spatial assessment of sperm whale strandings in NZ and highlights the need for future research on movements and genetic exchange between NZ sperm whales and sperm whales in the wider Pacific region.

Ecosystem Response Through a Resilience Lens: Do Differences in the Illinois River Over 150 Y Indicate Regime Shifts?

AbstractMost of the world's large river ecosystems are subject to multiple anthropogenic stressors including climate change, disconnection between the main river channel and floodplain, flow regulation, and land‐use modification. Viewed through a resilience lens, these ecosystems are potentially in a new regime, exhibiting a different structure, function, and set of feedbacks. We investigated the trophic status and food web character response to anthropogenic stressors over 150 years in the Illinois River. Differences in stable isotope ratios, community niche space, basal resource contribution to higher levels in the food web, mean trophic position of fish functional feeding guilds, and food chain length among four stressor phases suggest changes in ecosystem function in the Illinois River. Moreover, the river did not return to pre‐stressor conditions following watershed‐wide restoration efforts. Differences in trophic status and food web character also varied between the upper‐ and lower‐river zones of the Illinois River over time. This spatial divergence further highlights the complexity of responses to multiple stressors in this ecosystem. Overall, differences in trophic status and food web character suggest a shift to a new regime–an Anthropocene regime–and one that has a reduced capacity to absorb additional disturbances. Given human pressures are a global issue, our results based on a 150 years data set, could assist in the management of riverine landscapes that face regime shifts due to human stressors.

Comparative analysis of the feeding habits of Rapana venosa and Neptunea arthritica cumingii near Zhangzi Island, China, based on stable isotope ratios and fatty acid profiles

The two whelks Rapana venosa and Neptunea arthritica cumingii are important fishery resources, but the biomass of these species has declined extensively over the years. In the present study, we selected the sea area around Zhangzi Island, a typical North China Sea island, as the study area. Biochemical trophic markers (stable isotopes and fatty acids (FAs)) were used to estimate the dietary compositions of R. venosa and N. arthritica cumingii. The combined use of stable isotope analysis and analysis of FA composition enabled a comprehensive investigation of these species in the North China Sea. The results showed that the two whelk species were significantly distinguished by their FAs, suggesting that dietary composition significantly differs between the two species; however, the values of C22:6(n-3) (DHA)/C20:5(n-3) (EPA) and δ15N indicated no significant difference between the two whelk species at the trophic level. The EPA content of N. arthritica cumingii was higher than that of R. venosa, indicating that the former species is more involved in the scavenger food chain, although this FA species represented a small proportion of the dietary composition in both whelk species. In contrast, there were no significant differences in stable isotope ratios or FA contents among different size classes of the same whelk species. This study provides insight into the structural changes and dynamics of marine communities. Such information is essential for the protection of fishery resources, their sustainable development and utilization, and the scientific management of marine ecosystems.

Inter-individual variation in the diet within a group of Japanese macaques and its relationship with social structure investigated by stable isotope and DNA analyses.

We investigated individual variation in diet in relation to age-sex class and kin relationship in 28 of 40 members of a small group of wild Japanese macaques (Macaca fuscata). We used stable isotope ratios from hair as an index of individual dietary profiles, genetic relatedness as an index of kin relationship, and mitochondrial DNA (mtDNA) haplotype as a marker of being an immigrant or native member of the group. The range of carbon and nitrogen stable isotope ratios from hair of individual macaques (δ13C: -24.1‰ to -22.6‰, δ15N:3.8-5.5‰), which reflected their diet over a period of ~ 6months, implied small individual variation in diet. The results of PERMANOVA implied that there were no significant effects of age class, sex, or mtDNA haplotype on hair stable isotope ratios between individuals, or on the variation in individual diet. However, the isotope values of males with mtDNA haplotypes that differed from those of the native females appeared to differ from those of other group members, which implies that immigrant males might have had a different diet profile from that of native group members. Furthermore, there was a weak correlation trend between genetic relatedness and differences in stable isotope ratios between pairs of individuals. Differences in stable isotope values were more marked in pairs with a more distant genetic relationship. This implies that within the group, closely related kin tended to forage together to avoid competing for food. However, this effect might have been weak because the size of the group was small relative to the size of the food patches, thereby reducing competition.

Stable isotope analyses reveal seasonal and inter-individual variation in the foraging ecology of sperm whales

Studying inter-individual variation in foraging by top predators is key for understanding the ecology of their populations, while knowledge of seasonal variability in foraging helps explain temporal changes in habitat use and ecological role. We investigated the inter-individual and seasonal differences in stable isotope ratios of sperm whales Physeter macrocephalus in the temperate foraging ground of the Kaikóura Canyon, New Zealand. Isotope ratios of carbon and nitrogen were measured in 107 samples of sloughed skin from 37 individual males with a wide range of residency patterns and body lengths, sampled over 4 summers and 3 winters. Variability in individual isotope ratios was analysed with generalised additive mixed models. The whales’ residency patterns, but not body size, accounted for most heterogeneity of δ13C and δ15N. Specifically, whales that visited Kaikóura occasionally had more diverse and lower isotope ratios than more frequent visitors (by ca. -1‰ δ13C and -2‰ δ15N), likely reflecting a range of foraging habitats further offshore and/or south of Kaikóura Canyon. We suggest that these patterns reflect differences in large-scale foraging patterns within the population. In addition, whales sampled in winter had significantly lower values of δ13C than whales sampled in summer (by ca. -0.5‰), indicating seasonal differences in the use of food resources. Our results provide new insights into foraging patterns of sperm whales, and highlight the value of accounting for individual differences in the ecology of top predators.

Wait your turn, North Atlantic fin whales share a common feeding ground sequentially

Highly migratory marine species pose a challenge for the identification of management units due to the absence of clear oceanographic barriers. The population structure of North Atlantic fin whales has been investigated since the start of whaling operations but is still the subject of an ongoing scientific debate. Here we measured stable isotopes of carbon, nitrogen and oxygen in skin samples collected from 151 individuals from western Iceland, Galicia (NW Spain), the Azores archipelago and the Strait of Gibraltar (SoG). We found spatiotemporal differences in stable isotope ratios suggesting that fin whales sampled in these four areas may share a common feeding ground within the Northeast Atlantic at different times during the year. Our results also suggest that SoG whales use this common feeding ground in summer but exploit Mediterranean resources during the winter months, further supporting the existence of a limited but current exchange of individuals between these two basins.

Effect of different healing stages on stable isotope ratios in skeletal lesions.

Physiological stress is one of the various factors that can have an impact on stable isotope ratios. However, its effect on bone collagen stable isotope ratios is still not fully understood. This study aims to build on previous research on how different disease stages may affect bone collagen stable isotope ratios. Carbon (δ13 C) and nitrogen (δ15 N) isotope ratios were assessed in 33 skeletons that retained evidence of infectious disease and healed fractures. Samples were taken from active lesions (long bones n = 14; ribs n = 4), healed lesions (long bones n = 10; ribs n = 9), or a fracture callus (long bones n = 9; ribs n = 3). Results were compared to stable isotope ratios calculated for regions on these bones that did not retain evidence of disease or fracture. Long bones with active lesions had a significantly higher average δ15 N (δ15 N = 11.1 ± 0.9‰) compared to those without lesions (δ15 N = 10.7 ± 0.7‰; p = .02), while fracture calluses showed the largest range for both δ15 N and δ13 C. There were no significant differences in stable isotope ratios when compared between nonlesion and lesion sites in the ribs. The increase in δ15 N seen in active lesions, when compared with δ15 N from nonlesion regions on the same long bone, may be a consequence of altered protein metabolism. The high variability of δ15 N and δ13 C in fractures may be related to different healing stages of the calluses. This study suggests that stable isotope data can contribute information about diseases in the past, as well as an individual's response to diseases in the absence of modern medicine and antibiotics.

Late Cretaceous fluvial hydrology and dinosaur behavior in southern Utah, USA: Insights from stable isotopes of biogenic carbonate

During the Late Cretaceous, North America was flooded by the epieric Western Interior Seaway. Mountain building events on the western landmass fed sediment to broad, low relief fluvial systems, which preserve rich dinosaur-bearing fossil assemblages. In this study, stable isotope ratios of associated vertebrate and invertebrate material from the Kaiparowits Formation of southern Utah are used to investigate the nature of these hydrological systems and behavior of dinosaurs over these landscapes. Differences in stable isotope ratios of gar ganoine, enamel from hadrosaurid teeth, and authigenic micrite, in conjunction with previously published bivalve data, indicate a tripartite fluvial system consisting of large rivers draining upland areas, smaller streams draining the foreland basin, and lakes subject to unusual patterns of recharge. Specifically, mixing of water from large rivers and lakes occurred during seasonal flooding events analogous to processes taking place in modern-day Tonle Sap Lake in central Cambodia. Episodic flooding created heterogeneity among soils, with those proximal to permanent lake shores saturated for a longer period of time compared to more distal localities. Hadrosaurids consuming vegetation closer to lake shores have higher carbon isotope ratios in their tooth enamel than hadrosaurids consuming vegetation from more distal areas suggesting a difference in habitat use. Thus, variations in the paleohydrology of these fluvial systems appear to have played an important role in determining the distribution of dinosaurs over the Kaiparowits floodplain.

Study on the meat isotopic composition for origin identification

Russian consumer and governmental authorities are equally concerned to know where food products come from. This requires more accurate and specialized methods for the evaluation of geographical location. The following methods are used: chemometrics, histological and histochemical, genomic and proteomic, microbiological, immunochemical and mass spectrometric. Method of stable isotope analysis is becoming increasingly promising nowadays for the identification of meat and meat products' place of origin. The isotope ratios of the four elements - carbon, nitrogen, oxygen and hydrogen, are mainly determined. The method is successfully used to identify a country of origin of wines, juices and water. The aim of the research was to study the stable isotope ratios for pork and beef samples purchased in Moscow supermarkets (Russian Federation). The country of production of meat samples was determined according to specifications and/or labels. The geography of countries of meat samples origin includes Europe, both America continents and Australia. Databases collected by the All-Russian Scientific Research Institute of the Brewing, Non-Alcoholic and Wine Industrywere used for the analysis and interpretation of the results. Values of 13С/12С, δ13С, 18О/16О, δ18О, 2Н/1Н, δ2Н for 30 pork and beef samples from 13 countries were obtained. Differences in stable isotope ratios were found depending on place of origin. The data correlated with the oxygen isotope characteristics for wine, which were in the range from 2.5 to 4.5 ppm. According to the 13С/12С, δ13С results, the assumption was made about a false indication of the region for the beef sample. Despite the fact that beef was labeled as a product of Lithuania, the region of origin was most probably defined as Germany. The studies carried out showed the possibility to identify the region of raw meat origin by the stable isotope ratio.

Changes in the trophic status of fish feeding guilds in response to flow modification

AbstractRivers are among the most extensively modified ecosystems globally. Identifying linkages between critical drivers of change and ecological response is challenging because of the myriad of ways rivers are modified. This study examines longer‐term relationships (>70 years) between the trophic status of fish and historical flow changes in rivers of the Mississippi Basin. The flow regime of each river is regulated but differs in terms of character of hydrological modification. Tissue samples from specimens obtained from museum collections were used for determination of carbon and nitrogen stable isotope ratios. Questions asked were as follows: (1) Are there differences in stable isotope ratios of fish feeding guilds prior to and following hydrological modification? (2) What hydrological attributes are associated with isotopic changes? And (3) are corresponding changes in stable isotope ratios and hydrology identifiable across different spatial scales? Significant and sustained changes in stable isotope ratios of fish feeding guilds occurred immediately following flow regulation in all rivers. These changes were not associated with human‐induced biogeochemical alterations. The subsequent response was complex because (1) different guilds exhibited pronounced shifts in isotopic ratios, (2) hydrological modification differed between rivers, and (3) differences in stable isotopic ratios varied between spatial scales.

Diet, social differentiation and cultural change in Roman Britain: new isotopic evidence from Gloucestershire

This study uses stable isotope analyses (δ13C and δ15N) of human bone collagen to reconstruct the diet of three Romano-British (first to early fifth century AD) populations from Gloucestershire in South West England. Gloucestershire was an important part of Roman Britain with two major administrative centres at Gloucester (Glevum) and Cirencester (Corinium) and numerous smaller settlements and farmsteads. To investigate potential dietary differences between the rural and urban populations of Roman Gloucestershire, we compared human bone collagen stable isotope values from 32 individuals from urban Gloucester with those of 46 individuals from two rural cemeteries at Horcott Quarry and Cotswold Community, respectively. Seven individuals from urban Gloucester were buried in a mass grave; all others were buried in single inhumations. Results show small but significant differences in stable isotope ratios between the urban and rural populations which indicate that the urban population might have consumed slightly more marine and/or freshwater resources than the people living in the rural communities. We interpret this difference as a direct reflection of Rome’s influence on Gloucester’s population and the town’s economic status. Subtle differences in stable isotope ratios were also observed at the site level, as burial practice does correlate with diet in some cases. Overall, the results from this study demonstrate that diet, as reconstructed through stable isotope analysis, is a very sensitive, if settlement-specific, indicator of social differentiation and culture change.

Intergroup variation in stable isotope ratios reflects anthropogenic impact on the Barbary macaques (Macaca sylvanus) of Gibraltar

Interactions with humans impact many aspects of behavior and ecology in nonhuman primates. Because of the complexities of the human-nonhuman primate interface, methods are needed to quantify the effects of anthropogenic interactions, including their intensity and differential impacts between nonhuman primate groups. Stable isotopes can be used to quickly and economically assess intergroup dietary variation, and provide a framework for the development of specific hypotheses about anthropogenic impact. This study uses stable carbon and nitrogen isotope analysis to examine intraspecific variation in diet between five groups of Barbary macaques, Macaca sylvanus, in the Upper Rock Nature Reserve, Gibraltar. Analysis of hair from 135 macaques showed significant differences in δ(13)C and δ(15)N values between a group with minimal tourist contact and groups that were main tourist attractions. Because we observed no overt physiological or substantial behavioral differences between the groups, feeding ecology is the most likely cause of any differences in stable isotope ratios. Haphazard provisioning by tourists and Gibraltarians is a likely source of dietary variation between groups. Stable isotope analysis and observational data facilitate a deeper understanding of the feeding ecology of the Barbary macaques relevant to the role of an anthropogenic ecology for the species.

Temporal and spatial variation in the δ15N and δ13C values of fish and squid from Alaskan waters

To test the hypothesis that stable isotope ratios from marine organisms vary, the δ15N and δ13C values from fish and squid collected in Alaskan waters were measured across years (1997, 2000, and 2005), seasons, geographic locations, and different size/age classes, and between muscle tissue and whole animals. Temporal, geographic, and ontogenetic differences in stable isotope ratios ranged from 0.5–2.5‰ (δ15N) to 0.5–2.0‰ (δ13C). Twenty-one comparisons of stable isotope values between whole organisms and muscle tissue revealed only four small differences each for δ15N and δ13C, making costly and space prohibitive collection of whole animals unnecessary. The data from this study indicate that significant variations of stable isotope values from animals in marine systems necessitates collection of prey and predator tissues from the same time and place for best interpretation of stable isotope analysis in foraging ecology studies.

Differences in stable isotope ratios of Dall’s porpoises (Phocoenoides dalli) between coastal and oceanic areas of the North Pacific

AbstractCarbon and nitrogen stable isotope ratios in the muscle of Dall’s porpoises were measured. Samples were collected from the catches of the hand harpoon fishery, incidental catches of drift net, and scientific research on the use of drift nets. Samples were from the North Pacific, Sea of Japan, Sea of Okhotsk, and Bering Sea. Although no variation in δ15N was observed, δ13C was significantly different between population groups near Japan and the oceanic North Pacific and Bering Sea. The difference may be due not only to local variation in prey species, but also to an overall difference in carbon stable isotope ratios that originate from coastal benthic or oceanic pelagic‐based food webs. We differentiated Dall’s porpoise population groups from both areas using carbon stable isotope ratios with an error rate of <5%. Although further study is needed, our results suggest that carbon stable isotope ratios could possibly be an indicator of whether a Dall’s porpoise belongs to a coastal benthic or oceanic pelagic food web.

Vertical heterogeneity of a forest floor invertebrate food web as indicated by stable‐isotope analysis

AbstractDiverse populations of invertebrates constitute the food web in detritus layers of a forest floor. Heterogeneity in trophic interactions within such a species‐rich community food web may affect the dynamic properties of biological communities such as stability. To examine the vertical heterogeneity in trophic interactions among invertebrates in litter and humus layers, we studied differences in species composition and variations in carbon and nitrogen stable‐isotope ratios (δ13C and δ15N) using community‐wide metrics of the forest floors of temperate broadleaf forests in Japan. The species composition differed between the two layers, and the invertebrates in the litter layer were generally larger than those in the humus layer, suggesting that these layers harbored separate food webs based on different basal resources. However, the δ13C of invertebrates, an indicator of differences in the basal resources of community food webs, did not provide evidence for separate food webs between layers even though plant‐derived organic matter showed differences in stable‐isotope ratios according to decomposition state. The minimum δ15N of invertebrates also did not differ between layers, suggesting sharing of food by detritivores from the two layers at lower trophic levels. The maximum and range of δ15N were greater in the humus layer, suggesting more trophic transfers (probably involving microorganisms) than in the litter layer and providing circumstantial evidence for weak trophic interactions between layers at higher trophic levels. Thus, the invertebrate community food web was not clearly compartmentalized between the detrital layers but still showed a conspicuous spatial (vertical) heterogeneity in trophic interactions.