ANALYSIS OF DIETS OF UPLAND BUZZARDS USING STABLE CARBON AND NITROGEN ISOTOPES

This research investigates the potential of a new, noninvasive method for determining age of weaning among primates using stable carbon and nitrogen isotope ratios in feces. Analysis of stable isotope ratios in body tissues is a well-established method in archeology and ecology for reconstructing diet. This is the first study to investigate weaning in primates using fecal stable isotope ratios. Diets of a single François' langur (Trachypithecus francoisi) mother-infant pair at the Toledo Zoo are reconstructed using this technique to track changes in infant suckling behavior over the weaning period. Stable isotope ratios in feces are sampled instead of more traditional samples such as bone or hair to enable daily, noninvasive snapshots of weaning status. Isotopic assessments of weaning status are compared to visual assessments to identify any discordance between the two. Three measurements documented the transition from breast milk to solid foods: stable carbon isotope ratios (δ(13)C), stable nitrogen isotope ratios (δ(15)N), and nitrogen content of feces (%N). It appears that solid foods were introduced at approximately 2 months of infant age, but that nursing continued into the 12th month, when sample collection ceased. Stable isotope data exposed a much longer weaning period than what was expected based on previously published data for captive langurs, and clarified visual estimates of weaning status. This reflects the method's sensitivity to suckling at night and ability to distinguish actual nursing from comfort nursing. After testing this method with zoo animals, it can readily be applied among wild populations. An isotopic approach to weaning provides a new, accurate, and biologically meaningful assessment of interbirth intervals, and facilitates a better understanding of mother-infant interactions. Both of these outcomes are critical for developing successful conservation strategies for captive and wild primates.

Stable carbon and nitrogen isotope ratios as indicators of water status and nitrogen effects on peach trees

Data from a combination of laboratory and fieldwork is presented to initiate testing of stable carbon and nitrogen isotope ratios to trace sources of TNT in contaminated soil and groundwater. Evaluation of these extraction methods resulted in 99.9 and 99.8% recovery of TNT with Soxhlet and solid-phase extraction (SPE), respectively. As a result of the high extraction efficiency, isotope fractionation did not occur, thus providing an accurate stable isotope value on TNT from laboratory and field samples. Subsequent experiments evaluated the stability of isotope signatures through incubations lasting up to four weeks with a 70% decline in the TNT concentration. During these experiments, no significant variation in stable carbon and nitrogen isotope ratios was measured. Five different sources of TNT, compared for stable carbon and nitrogen isotope ratios, showed a range of 4.2 and 15%, respectively. This large range in the isotope ratios suggests excellent potential to trace sources in a complex environment. Finally, a site was surveyed for concentrations and isotope values of TNT extracted from groundwaters. Values from this site were substantially different relative to the variation measured on standards and in laboratory incubation experiments. The data set indicates good potential to use stable isotopes to determine TNT sources and fate in the environment.

Modeling trophic positions of the alpine meadow ecosystem combining stable carbon and nitrogen isotope ratios

The eastern hive bee Apis cerana is a major honeybee species in Asia providing numerous ecosystem services. Understanding how much the honeybees depend on natural and human-influenced plants and landscapes in different climates is important could contribute to evaluate how wild honeybees use food resources and to measure the ecosystem services. We investigated the effects of land use and climate changes on stable nitrogen and carbon isotope ratios in wild populations of A. cerana. In populations from 139 individual sites throughout Japan, we measured nitrogen (δ15N) and carbon (δ13C) stable isotope ratios and analyzed the effects of land use and climate. Our results showed that forested areas and annual precipitation had significant effects on δ15N, and that paddy fields and urban areas had significant effects on δ13C. These results suggest that A. cerana sensibly uses available food resources in the various environments and that stable nitrogen and carbon isotope ratios clearly reflect the effects of land use and climate changes on the populations of A. cerana. Thus, stable nitrogen and carbon isotope ratios in A. cerana, which widely distributes in Asia, can be used as indicators of the environments, such as land use and climate, of an area within its foraging range.

We studied the potential for using stable carbon and nitrogen isotope ratios in sediment profiles to trace external nutrient sources and eutrophication at four coastal sites in the Baltic Sea. The sites are characterized by various present and past activities in their catchments, including residential development, sugar processing, agriculture and fish farming. Radiometrically dated sediment cores were analysed for nutrient isotope ratios, organic carbon and total nitrogen. Background information was collected from historical sources, literature and water monitoring data. Despite the multiple organic enrichment sources, it was possible to identify individual sources and processes in the sediment profiles using stable isotope analysis of bulk sediment. The largest changes in δ15N values were seen at sites receiving urban wastewaters. The site that received effluents from a sugar cane (C4-plant) refinery in the past showed a clear effect on δ13C values compared to the site that received wastewater from a sugar beet (C3-plant) factory. Fish farming produced detectable, albeit minor changes in the sediment profile. Slightly lower δ13C values reflected the influence of fish feed and fish metabolism, and higher δ15N values likely indicated the influence of increased sediment denitrification. The land-sea connection via river discharge was observable in the overall δ13C levels of the sediment cores. Our results suggest that temporal changes in sources of organic matter enrichment can be detected in well-dated coastal sediment cores using nutrient stable isotope analyses, even at sites subjected to multiple impacts. There is not, however, a simple relationship between sediment stable isotope profiles and the eutrophication history of our study sites.

Stable nitrogen and carbon isotope ratios were measured from red blood cell (RBC) and serum components from 9 mo old Steller sea lions Eumetopias jubatus captured during February and March 2000 and 2001 from the Gulf of Alaska (GOA; Region 1, n = 11), the eastern Aleutian Islands (Region 3, n = 5), and the central Aleutian Islands (Region 4, n = 5) to assess their foraging ecology. Isotope ratios from sea lions were compared with those from probable prey species and results were compared with those from a study demonstrating regional differences in the diets of juvenile and adult sea lions through the use of scat analysis. Discriminant analyses using the δ 15 N and δ 13 C values of each blood component as the discriminant functions accurately classified sea lions to the appropri- ate foraging regions as predicted by a previous study employing scat analysis with an accuracy of 90% for serum and 95% for RBCs. The δ 15 N values reflect a decrease in sea lion trophic position mov- ing east to west that is probably driven by changes in sea lion diet. The δ 13 C values demonstrated clear distinctions between foraging locations that are likely driven by known geographic carbon isotope patterns observed in the GOA and along the Aleutian archipelago. Our data present further evidence that, in the marine environment, δ 13 C values do not covary with δ 15 N values as a result of trophic enrichment, and are better determinants of foraging location than trophic position.

Prolonged exposure to the stress hormone cortisol can precipitate a catabolic state in animals resulting in a negative nitrogen balance and increased excreted nitrogen, possibly affecting stable nitrogen and carbon isotope ratios in animal tissues. Here we test the hypothesis that stress, as measured by hair cortisol, is a significant contributor to variation in δ15 N and δ13 C values in hair. The results of the present study have important implications for the use of stable carbon and nitrogen isotope ratios measured in animal and human tissues to make inferences regarding feeding ecology and diet. Samples containing roughly 10-20 hairs (approx. 4-6 cm long) were collected from 49 free ranging macaque monkeys (Macaca sylvanus) in Gibraltar. Hair samples were analyzed for stable carbon and nitrogen isotopes by continuous-flow isotope-ratio mass spectrometry. Cortisol extracted from matched hair samples was measured using gas chromatography/mass spectrometry. Cortisol and stable isotope ratios were compared statistically using nonparametric Kruskal-Wallis and Mann-Whitney U tests, as well as Spearman correlation. Correlation analysis revealed that although hair δ15 N and δ13 C values were significantly correlated with each other, neither was correlated with cortisol concentrations. Cortisol concentrations were not correlated with age-adjusted body mass index. Age category was correlated with δ13 C values but not with δ15 N values. The results of our study suggest that the cumulative stress experienced by these macaques under typical social and environmental conditions is not a significant contributor to variation in δ15 N and δ13 C values, nor does it have a significant effect on relative body mass.

Effects of lipid extraction on human bone collagen: Comparing stable carbon and nitrogen isotope values with and without lipid extraction

Quantifying variability in stable carbon and nitrogen isotope ratios within the skeletons of marine mammals of the suborder Caniformia

Diet and disease in Tomar, Portugal: Comparing stable carbon and nitrogen isotope ratios between skeletons with and without signs of infectious disease

The skeletal remains of 18 individuals interred at the ancient Maya site of Caledonia (100 to 1000 C.E.), located in the Cayo District of Belize, w ere sampled for stable carbon and nitrogen isotope analysis in order to reconstruct their diet. Stable carbon and nitrogen isotope ratios in 18 bone collagen samples and stable carbon isotope ratios in bioapatite from 15 bone and 6 tooth enamel samples were assessed. Small sample sizes precluded the assessment of dietary variation with respect to age, sex, social status or time period among the Caledonia Maya. However, the sampled individuals consumed a varied diet consisting of maize, supplemented with some C3 plants, terrestrial herbivores and/or lower order freshwater resources such as snails and molluscs and possibly maize‐fed animals. This dietary variability with an emphasis on maize is unsurprising given the biological diversity surrounding the site and the known importance of this crop to the ancient Maya. As expected, the isotopic values from Caledonia are similar to those from nearby sites from similar time periods. However, four individuals exhibit a marine dietary signature, possibly indicating inland trade of marine resources from coastal sites, or the migration of coastal people to Caledonia. This study demonstrates the validity of sampling small, fragmented collections from minor Maya centres in order to gain valuable insight into ancient Maya dietary practices. Copyright © 2013 John Wiley & Sons, Ltd.

Stable carbon isotope ratios in prehistoric human bone collagen have been used extensively to document the introduction and intensification of maize horticulture in notheastern North America. Most previous studies are based on small samples of adults who are assumed to characterize the diet of the population. In this study, all 29 individuals buried within an Ontario Iroquoian village site dated A.D. 1530-1580 were analysed for stable isotopes of carbon and nitrogen. Age distribution of the sample ranges from preterm to elderly. Significant negative correlations between age and delta 13C, and age and delta 15N values were found. High delta 13C values in infants and young children (delta 13C = -6.8 to -12.3) suggest a weaning diet high in maize. High delta 15N values in infants relative to adults suggest a trophic level effect during breast-feeding which has been reported in a modern sample by Tuross et al. (Am. J. Phys. Anthropol., 1993). In addition to the isotopic evidence for extremely high carbohydrate (maize) intake, the MacPherson sample includes two juveniles aged 3-4 years, exhibiting circular caries. No other cases of this condition are known in the extensively studied southern Ontario skeletal collections. Together the evidence from dentition and stable carbon isotopes indicates a very high carbohydrate diet in subadults. Circular caries result from developmental stress during enamel formation with subsequent caries formation in areas of thinner enamel. These findings are relevant to studies of infant and early childhood morbidity and mortality among prehistoric maize horticulturists.

Oh, Y.; Sohn, H.; Lee, D.; An, Y.-R.; Kang, C.-K.; Kang, M.G., and Lee, S.H., 2018. Feeding patterns of ‘Finless porpoise (Neophocaena asiaeorientalis)’ in the yellow sea as indicated by stable carbon and nitrogen ratios. In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 386–390. Coconut Creek (Florida), ISSN 0749-0208.Finless porpoise (Neophocaena asiaeorientalis) is a representative marine mammal that has the largest habitat near the Korean coastal area. However, little information on their trophic ecology has been reported in Korea to date. The stable carbon and nitrogen isotope ratios from muscle samples (n = 60) were analyzed for their trophic ecology. The muscle tissues from the stranded or by caught porpoises in the Yellow Sea were obtained in 2015 (n = 37) and 2016 (n = 23) by Cetacean Research Institute in Korea. The averages of δ13C and δ15N for all the samples were −17.74 ‰ (S.D. = ±0.74 ‰) and 12.96 ‰ (S.D. = ±0.95 ‰), respectively. The mean isotopic values of the porpoise groups obtained from different seasons were −18.13 ‰ (±0.56 ‰) and 12.43 ‰ (±0.73 ‰) and −17.06 ‰ (±0.46 ‰) and 13.87 ‰ (±0.46 ‰) for summer (n = 38) and spring (n = 22), respectively, which were significantly different among the two seasons (t-test; p < 0.01, n = 60, respectively). These increasing isotope values from summer to spring reflected a shift in major prey sources. The small increasing in δ15N values could be caused partly by different body lengths of the porpoises. However, the most plausible reason for the large shift in δ13C value relative to δ15N could be a change from pelagic to benthic prey in the different seasons since benthic diets are reported for enriched δ13C over the pelagic diets. For better understanding, further validation should be conducted.

Stable carbon and nitrogen isotope ratios (13C/12C and 15N/14N) of primary producers and consumers were investigated seasonally throughout 1999, in order to describe the food web in a western Mediterranean coastal lagoon (Lake of Sabaudia, central Italy). Particulate organic matter and algal material (seagrass epiphytes and macroalgae) seem to constitute the main food sources for primary consumers (zooplankton and small benthic invertebrates, respectively) throughout the sampling year, while the seagrass Cymodocea nodosa appears to play a negligible trophic role. As regards the ichthyofauna, carbon stable isotopes differentiated between planktivore and benthivore fish species. However, a benthic–pelagic coupling seems to occur, with some fish of higher trophic levels feeding both on benthic and pelagic materials. Analysis of variance showed that the interaction between the three main factors (species×size×season) significantly affects the isotopic composition of fish, suggesting the presence of intra- and inter-specific resource partitioning. Wide seasonal variations in the isotopic composition were observed in organic matter sources, invertebrates and fish, with a general trend towards depleted values in winter and enriched values in summer. The winter depletion of organic matter sources may be due to several environmental factors and seems to be mirrored in the upper trophic levels. Primary producers and invertebrates are known to have shorter time-integrated isotopic signatures than vertebrates, yet fish also exhibited seasonal isotopic differences. We concluded that the examined fish species can assume a new muscle isotopic signature relatively quickly in response to changes in the isotopic composition of their diet and/or diet shifts.