Isotopic ecology of coyotes from scat and road kill carcasses: A complementary approach to feeding experiments.

Scat is frequently used to study animal diets because it is easy to find and collect, but one concern is that gross fecal analysis (GFA) techniques exaggerate the importance of small-bodied prey to mammalian mesopredator diets. To capitalize on the benefits of scat, we suggest the analysis of scat carbon and nitrogen isotope values (δ13C and δ15N). This technique offers researchers a non-invasive method to gather short-term dietary information. We conducted three interrelated studies to validate the use of isotopic values from coyote scat: 1) we determined tissue-to-tissue apparent C and N isotope enrichment factors (ε13* and ε15*) for coyotes from road kill animals (n = 4); 2) we derived diet-to-scat isotope discrimination factors for coyotes; and 3) we used field collected coyote scats (n = 12) to compare estimates of coyote dietary proportions from stable isotope mixing models with estimates from two GFA techniques. Scat consistently had the lowest δ13C and δ15N values among the tissues sampled. We derived a diet-to-scat Δ13C value of -1.5‰ ± 1.6‰ and Δ15N value of 2.3‰ ± 1.3‰ for coyotes. Coyote scat δ13C and δ15N values adjusted for discrimination consistently plot within the isotopic mixing space created by known dietary items. In comparison with GFA results, we found that mixing model estimates of coyote dietary proportions de-emphasize the importance of small-bodied prey. Coyote scat δ13C and δ15N values therefore offer a relatively quick and non-invasive way to gain accurate dietary information

Integrating dual C and N isotopic approach to elemental and mathematical solutions for improving the PM source apportionment in complex urban and industrial cities: Case of Tarragona - Spain

Identification of dominant airborne Particulate Matter (PM) sources is essential for maintaining high air quality standards and thus ensuring a good public health. In this study, different approaches were applied for source apportionment of three PM fractions (PM1, PM2.5 and PM10) at the outdoor of 14 schools of a coastal city with a significant land use interweaving such as Tarragona (Spain). PM were collected in 24h-quartz microfiber filters in two seasonal campaigns (cold and warm), together with nine local potential sources, so a total of 84 samples were chemically, mineralogically, and isotopically characterised. Source apportionment was assessed by (i) main chemical components, (ii) Principal Component Analysis (PCA), (iii) dual C and N isotope approach, and (iv) a Bayesian isotope mixing model. When chemical concentrations were grouped into marine, crustal, secondary inorganic aerosols and organic matter + elemental carbon categories, the unaccounted component reached 45% of PM mass. The PCA allowed to identify also traffic and industrial contributions, reducing the unaccounted mass to about 25%. Adding δ13C and δ15N values, secondary organic aerosol could be estimated and a continuous contribution of diesel combustion was identified together with a remarkable use of natural gas in winter. Isotopic values were better understood when considering air masses back trajectories and a possible long-distance contribution from coal-fired electric generating units (EGUs). Finally, using Bayesian dual isotope mixing models, the unaccounted PM mass was reduced up to 5% when adding these EGUs to marine-carbonate related, road traffic, domestic heating, waste incinerator and livestock waste contributions. The added value of the dual isotope approach combined with a Bayesian isotope mixing model, in comparison with conventional chemical approaches, was thus demonstrated for PM source apportionment in an urban and industrial site where many sources and processes converge and can then be applied to other complex cities

Identifying bearded and ringed seal diet - a comparison of stomach contents, stable isotopes, fatty acids, and fecal dna

Thesis (M.S.) University of Alaska Fairbanks, 2014Stomach contents, stable isotopes, fatty acids, and more recently fecal DNA are commonly used to infer the diet of marine mammals. However, how complementary or contradictory these methods are, especially when considering individual diet variability, remains poorly understood. This study assessed the differences in the dietary information resulting from stomach contents, stable isotopes, and fatty acids for adult bearded seals (Erignathus barbatus), and fishes identified from stomach contents and fecal DNA for bearded and ringed seals (Pusa hispida), harvested in Alaska for subsistence use. Stomach contents and fecal DNA provided information on recently consumed prey. In contrast, stable carbon and nitrogen isotopes of muscle and fatty acid profiles of blubber provided information on prey consumed and integrated over a longer time frame, but taxonomic resolution of prey was low. Overall, stomach contents provided the most dietary data, while fecal DNA delivered the least. Using denaturing gradient gel electrophoresis (DGGE) of 16S gene fragments, only 40% of the fecal samples (12 bearded and one ringed seal) produced detectable DNA suitable for reference gene amplification. Only three fish species could be positively identified in the diet of seals (Arctic cod, Boreogadus saida; shorthorn sculpin, Myoxocephalus scorpius; and an unknown snailfish species, Liparidae) when using fecal DNA. In a dietary comparison, and despite differences in dietary time frames, the relative occurrence (RO) of prey from stomach contents and the mean proportions of prey source groups from a Bayesian stable isotope mixing model (SIAR) were similar. The proportions of indicator fatty acids from full-thickness blubber, such as 16:4n-1, 20:5n-3, 20:4n-6, 20:1n-9, 22:1n-11, and the presence of non-methylene-interrupted fatty acids were similar to other fatty acid studies of bearded seals in Alaska, and suggest a benthic diet. Overall, the methods yielded different, but not necessarily contradictory results.Chapter 1: General Introduction -- Chapter 2: Identifying bearded seal diet: a comparison of individual seals using stomach contents, stable isotopes, and fatty acids -- Chapter 3: Fish prey in bearded and ringed seal diet: a comparison of stomach contents and fecal DNA -- Chapter 4: General Conclusion

A mixed-method approach for the investigation of riverine nitrate pollution at catchment scale

It is important to have an insight into the fate of riverine nitrate at the catchment level. The idea is to apply different methods for one same study site, in order to overcome their limitations and take advantage of their strong points for the research. An approach with necessary steps were proposed to be conducted: 1) evaluation of the current nitrogen status in the water bodies; then 2) identification of the major nitrogen input sources; and when possible 3) development of a model which is able to simulate the nitrogen dynamics within the river catchment. A mixed-method approach, combining the experimental works (sampling campaigns and labs), statistical analysis (multivariate tool PCA, dual stable isotope tool), and modelling (isotope mixing model SIMMR, ecohydrological model SWAT) was proven to be an effective approach to investigate the fate of nitrogen, especially nitrate, at the river catchment level. In this dissertation, the Fuhse River catchment was chosen as the study site for investigating the status and dynamics of the riverine nitrate. The results from hydrochemical statistical analyses showed that water of the Fuhse River was an evolved type with mix abundances of ionic concentrations. It was classified into the main hydrochemical group of Ca-Cl-SO4, which represented that the water was influenced by anthropogenic activities. After that, the dual isotope method and the mixing model SIMMR indicated the soil nitrogen, manure and sewage as the predominant nitrate sources in this river water, which might lead to the nitrate of the river exceeding the natural threshold concentration. Finally, the incorporation of isotope results into SWAT has improved the robustness and the creditability of model. The nitrate loads were successfully simulated by the model

Quantifying Inter- and Intra-Population Niche Variability Using Hierarchical Bayesian Stable Isotope Mixing Models

Variability in resource use defines the width of a trophic niche occupied by a population. Intra-population variability in resource use may occur across hierarchical levels of population structure from individuals to subpopulations. Understanding how levels of population organization contribute to population niche width is critical to ecology and evolution. Here we describe a hierarchical stable isotope mixing model that can simultaneously estimate both the prey composition of a consumer diet and the diet variability among individuals and across levels of population organization. By explicitly estimating variance components for multiple scales, the model can deconstruct the niche width of a consumer population into relevant levels of population structure. We apply this new approach to stable isotope data from a population of gray wolves from coastal British Columbia, and show support for extensive intra-population niche variability among individuals, social groups, and geographically isolated subpopulations. The analytic method we describe improves mixing models by accounting for diet variability, and improves isotope niche width analysis by quantitatively assessing the contribution of levels of organization to the niche width of a population

Coyote (Canis latrans) use of marine resources in coastal California: A new behavior relative to their recent ancestors

Coyotes ( Canis latrans) are known to consume marine foods, but the importance and persistence of marine subsidies to coyotes is unknown. Recent access to a marine subsidy, especially if gained following apex predator loss, may facilitate coyote expansion along coastal routes and amplify the effects of mesopredator release. Our goal was to quantify and contextualize past and present marine resource use by coyotes on the central coast of California via stable isotope analysis. We measured δ13C and δ15N values in coyotes, their competitors, and their food resources at two modern sites, seven archaeological sites spanning in age from ~3000 to 750 BP, and from historical (AD 1893–1992) coyote and grizzly bear hair and bone sourced from coastal counties. We found evidence for marine resource use by modern coastal California coyotes at one site, Año Nuevo, which hosts a mainland northern elephant seal ( Mirounga angustirostris) breeding colony. Seals and sea lions account for ~20% of Año Nuevo coyote diet throughout the year and this marine subsidy likely positively impacts coyote population size. Isotopic data suggest that neither historic nor prehistoric coyotes consumed marine-derived foods, even at sites near ancient mainland seal rookeries. Marine resource use by some contemporary California coyotes is a novel behavior relative to their recent ancestors. We hypothesize that human alteration of the environment through extirpation of the California grizzly bear and the more recent protection of marine mammals likely enabled this behavioral shift

Stable Isotope clues to the formation and evolution of refrozen melt ponds on Arctic Sea ice.

Author Posting. © American Geophysical Union, 2018. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research-Oceans 123(12), (2018): 8887-8901, doi:10.1029/2018JC013797.Sea ice is one of the determining parameters of the climate system. The presence of melt ponds on the surface of Arctic sea ice plays a critical role in the mass balance of sea ice. A total of nine cores was collected from multiyear ice refrozen melt ponds and adjacent hummocks during the 2015 Arctic Sea State research cruise. The depth profiles of water isotopes, salinity, and ice texture for these sea ice cores were examined to provide information about the development of refrozen melt ponds and water balance generation processes, which are otherwise difficult to acquire. The presence of meteoric water with low oxygen isotope values as relatively thin layers indicates melt pond water stability and little mixing during formation and refreezing. The hydrochemical characteristics of refrozen melt pond and seawater depth profiles indicate little snowmelt enters the upper ocean during melt pond refreezing. Due to the seasonal characters of deuterium excess for Arctic precipitation, water balance calculations utilizing two isotopic tracers (oxygen isotope and deuterium excess) suggest that besides the melt of snow cover, the precipitation input in the melt season may also play a role in the evolution of melt ponds. The dual‐isotope mixing model developed here may become more valuable in a future scenario of increasing Arctic precipitation. The layers of meteoric origin were found at different depths in the refrozen melt pond ice cores. Surface topography information collected at several core sites was examined for possible explanations of different structures of refrozen melt ponds.The coauthors (S. F. A., S. S., T. M., and B. W.) wish to thank the other DRI participants and the Captain and crew of the Sikuliaq's October 2015 cruise for their assistance in the sample collections analyzed in the paper. Jim Thomson (Chief Scientist), Scott Harper (ONR Program Manager), and Martin Jeffries (ONR Program Manager) are particularly acknowledged for their unwavering assistance and leadership during the 5 years of the SeaState DRI. We thank Guy Williams for production of the aerial photo mosaic. Funding from the Office of Naval Research N00014‐13‐1‐0435 (S. F. A. and B. W.), N00014‐13‐1‐0434 (S. S.), and N00014‐13‐1‐0446 (T. M.) supported this research through grants to UTSA, UColorado, and WHOI, respectively. This project was also funded (in part) by the University of Texas at San Antonio, Office of the Vice President for Research (Y. G. and S. F. A.). Data for the stable isotope mixing models used in this study are shown in supporting information Tables S1–S3.2019-05-1