Triple Oxygen Isotope Measurements (Δ\u27\u3csup\u3e17\u3c/sup\u3eO) of Body Water Reflect Water Intake, Metabolism, and δ\u3csup\u3e18\u3c/sup\u3eO of Ingested Water in Passerines (original) (raw)
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Frontiers in Ecology and Evolution
Tracing how free-ranging organisms interact with their environment to maintain water balance is a difficult topic to study for logistical and methodological reasons. We use a novel combination of triple-oxygen stable isotope analyses of water extracted from plasma (δ16O, δ17O, δ18O) and bulk tissue carbon (δ13C) and nitrogen (δ15N) isotopes of feathers and blood to estimate the proportional contribution of marine resources, seawater, and metabolic water used by two species of unique songbirds (genus Cinclodes) to maintain their water balance in a seasonal coastal environment. We also assessed the physiological adjustments that these birds use to maintain their water balance. In agreement with previous work on these species, δ13C and δ15N data show that the coastal resident and invertivore C. nigrofumosus consumes a diet rich in marine resources, while the diet of migratory C. oustaleti shifts seasonally between marine (winter) to freshwater aquatic resources (summer). Triple-oxygen ...
Variations in stable hydrogen and oxygen isotope ratios in terrestrial animal tissues are used to reconstruct origin and movement. An underlying assumption of these applications is that tissues grown at the same site share a similar isotopic signal, representative of the location of their origin. However, large variations in tissue isotopic compositions often exist even among conspecific individuals within local populations, which complicates origin and migration inferences. Field-data and correlation analyses have provided hints about the underlying mechanisms of within-site among-individual isotopic variance, but a theory explaining the causes and magnitude of such variance has not been established. Here we develop a mechanistic modeling framework that provides explicit predictions of the magnitude, patterns, and drivers of isotopic variation among individuals living in a common but environmentally heterogeneous habitat. The model toolbox includes isoscape models of environmental isotopic variability, an agent-based model of behavior and movement, and a physiology-biochemistry model of isotopic incorporation into tissues. We compare model predictions against observed variation in hatch-year individuals of the songbird Spotted Towhee (Pipilo maculatus) in Red Butte Canyon, Utah, and evaluate the ability of the model to reproduce this variation under different sets of assumptions. Only models that account for environmental isotopic variability predict a similar magnitude of isotopic variation as observed. Within the modeling framework, behavioral rules and properties govern how animals nesting in different locations acquire resources from different habitats, and birds nesting in or near riparian habitat preferentially access isotopically lighter resources than those associated with the meadow and slope habitats, which results in more negative body water and tissue isotope values. Riparian nesters also have faster body water turnover Magozzi et al.
Non‐invasive measurement of metabolic rates in wild, free‐living birds using doubly labelled water
Functional Ecology, 2018
Doubly labelled water (DLW) is routinely used to measure energy expenditure and water turnover in free‐ranging animals. Standard methods involve capture, blood sampling for baseline measurement, injection with isotopic tracers, captivity for an equilibration period, post‐dose blood sampling, release and subsequent recapture for final blood sampling. Single sampling methods that minimise disturbance by reducing capture and handling time have been developed and tested. Sampling faeces rather than blood could further reduce disturbance to study animals in a range of species and study systems. However, the extent to which estimates of metabolic rate derived from blood and faecal samples diverge has not been investigated. We compared isotopic enrichment in blood and faecal samples taken concurrently from captive Southern Pied Babblers Turdoides bicolor. Isotopic enrichment levels in faeces and in blood were used to calculate initial and final ratios of for each individual. We then used t...
Fluxes of carbon, nitrogen, and water between ecosystem components and organisms have great impacts across levels of biological organization. Although much progress has been made in tracing carbon and nitrogen, difficulty remains in tracing water sources from the ecosystem to animals and among animals (the ‘‘water web’’). Naturally occurring, nonradioactive isotopes of hydrogen and oxygen in water provide a potential method for tracing water sources. However, using this approach for terrestrial animals is complicated by a change in water isotopes within the body due to differences in activity of heavy and light isotopes during cuticular and transpiratory water losses. Here we present a technique to use stable water isotopes to estimate the mean mix of water sources in a population by sampling a group of sympatric animals over time. Strong correlations between H and O isotopes in the body water of animals collected over time provide linear patterns of enrichment that can be used to predict a mean mix of water sources useful in standard mixing models to determine relative source contribution. Multiple temperature and humidity treatment levels do not greatly alter these relationships, thus having little effect on our ability to estimate this population-level mix of water sources. We show evidence for the validity of using multiple samples of animal body water, collected across time, to estimate the isotopic mix of water sources in a population and more accurately trace water sources. The ability to use isotopes to document patterns of animal water use should be a great asset to biologists globally, especially those studying drylands, droughts, streamside areas, irrigated landscapes, and the effects of climate change.
Oecologia, 2004
Naturally-occurring deuterium stable isotope ratios can potentially be used to trace water resource use by animals, but estimating the contribution of isotopically distinct water sources requires the accurate prediction of isotopic discrimination factors between water inputs and an animal's body water pool. We examined the feasibility of using estimates of water fluxes between a bird and its environment with a mass-balance model for the deuterium stable isotope ratio of avian body water (δD body ) to predict isotopic discrimination factors. Apparent fractionation and thus discrimination factors were predicted to vary with the proportion of an animal's total water losses than could be attributed to evaporative processes. To test our ability to predict isotopic discrimination, we manipulated water intake and evaporative water loss in rock doves (Columba livia) by providing them with fresh water or 0.15 M NaCl solution in thermoneutral or hot environments. After we switched the birds from drinking water with δD=−95‰ VSMOW (Vienna Standard Mean Ocean Water) to enriched drinking water with δD=+52‰ VSMOW, steady-state δD body was approached asymptotically. The equilibrium δD body was enriched by 10-50‰ relative to water inputs. After isotopic equilibrium was reached, the degree of enrichment was positively related (r 2 =0.34) to the fraction of total water loss that occurred by evaporation r evap =r H 2 O À Á supporting the major prediction of the model. The variation we observed in discrimination factors suggests that the apparent fractionation of deuterium will be difficult to predict accurately under natural conditions. Our results show that accurate estimates of the contribution of different water sources to a bird's body water pool require large deuterium isotopic differences between the sources.
Oxygen isotope fractionation between bird bone phosphate and drinking water
Die Naturwissenschaften, 2017
Oxygen isotope compositions of bone phosphate (δ(18)Op) were measured in broiler chickens reared in 21 farms worldwide characterized by contrasted latitudes and local climates. These sedentary birds were raised during an approximately 3 to 4-month period, and local precipitation was the ultimate source of their drinking water. This sampling strategy allowed the relationship to be determined between the bone phosphate δ(18)Op values (from 9.8 to 22.5‰ V-SMOW) and the local rainfall δ(18)Ow values estimated from nearby IAEA/WMO stations (from -16.0 to -1.0‰ V-SMOW). Linear least square fitting of data provided the following isotopic fractionation equation: δ(18)Ow = 1.119 (±0.040) δ(18)Op - 24.222 (±0.644); R (2) = 0.98. The δ(18)Op-δ(18)Ow couples of five extant mallard ducks, a common buzzard, a European herring gull, a common ostrich, and a greater rhea fall within the predicted range of the equation, indicating that the relationship established for extant chickens can also be appl...
Doubly Labeled Water Validation in the Marsupial Petauroides-Volans
Australian Journal of Zoology, 1990
Amounts of carbon dioxide (C02) produced by caged greater gliders were measured simultaneously by means of potassium hydroxide absorption, and by the low-level, doubly labelled water method, which incorporated a gas isotope ratio mass spectrometer for determining the low oxygen isotope enrichments. The two methods yielded significantly different values, but doubly labelled water underestimated C 0 2 production by only 8.3% on average, and this error is in the range of mean errors found in previous validation studies where no significant differences existed. In addition, we tested procedures designed to reduce the costs of using the doubly labelled water method, by streamlining field and laboratory procedures for sample handling and processing.
Chemical Geology, 2018
Blood oxygen isotopes Body water oxygen isotopes δ 18 O of milk δ 18 O Physiology Evaporative water loss Large herbivores Sheep Seasonality A B S T R A C T Mammalian body, blood and hard tissue oxygen isotope compositions (δ 18 O values) reflect environmental water and food sources, climate, and physiological processes. For this reason, fossil and archaeological hard tissues, which originally formed in equilibrium with body chemistry, are a valuable record of past climate, landscape paleoecology, and animal physiology and behavior. However, the environmental and physiological determinants of blood oxygen isotope composition have not been determined experimentally from large herbivores. This class of fauna is abundant in Cenozoic terrestrial fossil assemblages, and the isotopic composition of large herbivore teeth has been central to a number of climate and ecological reconstructions. Furthermore, existing models predict blood water, or nearly equivalently body water, δ 18 O values based on environmental water sources. These have been evaluated on gross timescales, but have not been employed to track seasonal variation. Here we report how water, food, and physiology determine blood water δ 18 O values in experimental sheep (Ovis aries) subjected to controlled water switches. We find that blood water δ 18 O values rapidly reach steady state with environmental drinking water and reflect transient events including weaning, seasons, and snowstorms. Behavioral and physiological variation within a single genetically homogenous population of herbivores results in significant inter-animal variation in blood water δ 18 O values at single collection times (1 s.d. = 0.1-1.4‰, range = 3.5‰) and reveals a range of water flux rates (t 1/2 = 2.2-2.9 days) within the population. We find that extant models can predict average observed sheep blood δ 18 O values with striking fidelity, but predict a pattern of seasonal variation exactly opposite of that observed in our population for which water input variation was controlled and the effect of physiology was more directly observed. We introduce to these models an evaporative loss term that is a function of environmental temperatures. The inclusion of this function produces model predictions that mimic the observed seasonal fluctuations and match observations to within 1.0‰. These results increase the applicability of available physiological models for paleoseasonality reconstructions from stable isotope measurements in fossil or archaeological enamel, the composition of which is determined in equilibrium with blood values. However, significant blood δ 18 O variation in this experimentally controlled population should promote caution when interpreting isotopic variation in the archaeological and paleontological record.
Tracking migratory animals has benefitted using measurements of naturally occurring stable isotopes of hydrogen (d 2 H) in keratinous tissues such as hair and feathers to link animal origins to continental patterns or isoscapes of d 2 H in precipitation. However, for most taxa, much less information exists on the use of stable oxygen isotope ratios (d 18 O) despite the fact that d 2 H and d 18 O are strongly linked in environmental waters through the meteoric relationship and the possibility of using both isotopes to infer greater information on origins and climatic conditions where tissues are grown. A fundamental requirement of using stable isotopes to assign individuals and populations to origins is the development of a rescaling function linking environmental food web signals to the tissue of interest and for birds, this has not been carried out. Here, we derived the relationship between H and O isotopes in known source feathers of 104 individuals representing 11 species of insectivorous passerines sampled across the strong precipitation isoscape of North America. We determined again a strong expected relationship between feather d 2 H (d 2 H f ) and long-term amount-weighted precipitation d 2 H (d 2 H p ; r 2 = 0.77), but the corresponding relationship between d 18 O f and d 18 O p was poor (r 2 = 0.32) for the same samples. This suggests that d 2 H measurements are currently more useful for assignment of insectivorous songbirds to precipitation isoscapes but does not preclude other uses of the d 18 O f data. Currently, mechanisms responsible for the decoupling of H and O isotopes in food webs is poorly known, and we advocate a much broader sampling of both isotopes in the same keratinous tissues across precipitation isotope gradients and across taxa to resolve this issue and to increase the power of using water isotopes to track migratory animals.
Probing the metabolic water contribution to intracellular water using oxygen isotope ratios of PO4
Proceedings of the National Academy of Sciences of the United States of America, 2016
Knowledge of the relative contributions of different water sources to intracellular fluids and body water is important for many fields of study, ranging from animal physiology to paleoclimate. The intracellular fluid environment of cells is challenging to study due to the difficulties of accessing and sampling the contents of intact cells. Previous studies of multicelled organisms, mostly mammals, have estimated body water composition-including metabolic water produced as a byproduct of metabolism-based on indirect measurements of fluids averaged over the whole organism (e.g., blood) combined with modeling calculations. In microbial cells and aquatic organisms, metabolic water is not generally considered to be a significant component of intracellular water, due to the assumed unimpeded diffusion of water across cell membranes. Here we show that the (18)O/(16)O ratio of PO4 in intracellular biomolecules (e.g., DNA) directly reflects the O isotopic composition of intracellular water a...