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Field studies suggest that changes in the stable isotope ratios of phytoplankton communities can be used to track changes in the utilization of different nitrogen sources, i.e., to detect shifts from dissolved inorganic nitrogen (DIN) uptake to atmospheric nitrogen (N 2 ) fixation by diazotrophic cyanobacteria as an indication of nitrogen limitation. We explored changes in the stable isotope signature of the diazotrophic cyanobacterium Trichormus variabilis in response to increasing nitrate (NO 3 − ) concentrations (0 to 170 mg L −1 ) under controlled laboratory conditions. In addition, we explored the influence of nitrogen utilization at the primary producer level on trophic fractionation by studying potential changes in isotope ratios in the freshwater model Daphnia magna feeding on the differently grown cyanobacteria. We show that δ 15 N values of the cyanobacterium increase asymptotically with DIN availability, from -0.7 ‰ in the absence of DIN (suggesting N 2 fixation) to 2.9 ‰ at the highest DIN concentration (exclusive DIN uptake). In contrast, δ 13 C values of the cyanobacterium did not show a clear relationship with DIN availability. The stable isotope ratios of the consumer reflected those of the differently grown cyanobacteria but also revealed significant trophic fractionation in response to nitrogen utilization at the primary producer level. Nitrogen isotope turnover rates of Daphnia were highest in the absence of DIN as a consequence of N 2 fixation and resulting depletion in 15 N at the primary producer level. Our results highlight the potential of stable isotopes to assess nitrogen limitation and to explore diazotrophy in aquatic food webs.

Between the sixteenth and nineteenth century, British agriculture underwent a ‘revolutionary’ transformation. Yet despite over a century of research and the recognised centrality of agricultural developments to industrialisation and population growth, the character or chronology of any ‘revolution’ during this period remains contentious. Enquiry has been hampered by the fragmented and locally specific nature of historic accounts and the broad dating of early-modern zooarchaeological assemblages. To address this, we conducted stable isotope analysis on 658 legal documents written on sheepskin parchment; a unique biological resource that records the day, month and year of use (AD 1499 to 1969). We find these provide a high temporal resolution analysis of changing agricultural practices and episodes of disease. Most significantly, they suggest that if an ‘Agricultural Revolution’ occurred in livestock management, it did so from the mid-nineteenth century, in the aftermath of the Napoleonic Wars.

Competition for resources within a population can lead to niche partitioning between sexes, throughout ontogeny and among individuals, allowing con-specifics to co-exist. We aimed to quantify such partitioning in Antarctic fur seals, Arctocephalus gazella , breeding at South Georgia, which hosts ~95% of the world’s population. Whiskers were collected from 20 adult males and 20 adult females and stable isotope ratios were quantified every 5 mm along the length of each whisker. Nitrogen isotope ratios (δ 15 N) were used as proxies for trophic position and carbon isotope ratios (δ 13 C) indicated foraging habitat. Sexual segregation was evident: δ 13 C values were significantly lower in males than females, indicating males spent more time foraging south of the Polar Front in maritime Antarctica. In males δ 13 C values declined with age, suggesting males spent more time foraging south throughout ontogeny. In females δ 13 C values revealed two main foraging strategies: 70% of females spent most time foraging south of the Polar Front and had similar δ 15 N values to males, while 30% of females spent most time foraging north of the Polar Front and had significantly higher δ 15 N values. This niche partitioning may relax competition and ultimately elevate population carrying capacity with implications for ecology, evolution and conservation.

There have been numerous recent observations of changes in the behavior and dynamics of migratory bird populations, but the plasticity of the migratory trait and our inability to track small animals over large distances have hindered investigation of the mechanisms behind migratory change. We used habitat-specific stable isotope signatures to show that recently evolved allopatric wintering populations of European blackcaps Sylvia atricapilla pair assortatively on their sympatric breeding grounds. Birds wintering further north also produce larger clutches and fledge more young. These findings describe an important process in the evolution of migratory divides, new migration routes, and wintering quarters. Temporal segregation of breeding is a way in which subpopulations of vertebrates may become isolated in sympatry.

Rivers in urban locations frequently receive contaminated wastewater and particulate waste either directly from storm overflows or from sewage treatment facilities. Although many urban streams are now recovering from wide-scale historic pollution, lower-level effects on water chemistry, nutrients and biotic composition are still widespread. We aimed to determine whether such effects could be detected using stable isotope ratios (δ 15 N, δ 13 C and δ 34 S) in macroinvertebrates alone or in conjunction with traditional biomonitoring. Macroinvertebrates were collected upstream and downstream of 11 different secondary wastewater treatment works (WwTW) in South Wales and the Welsh borders (United Kingdom). Overall, mean invertebrate δ 15 N signatures downstream of the WwTW were significantly enriched despite variation amongst sites. Moreover, changes between upstream and downstream macroinvertebrate δ 15 N values were highly correlated with patterns in macroinvertebrate community composition, increased total macroinvertebrate abundance, and reduced Shannon Diversity and other biomonitoring indices (% EPT, % shredders and ASPT scores). Changes in invertebrate δ 15 N values also paralleled the consented discharge volumes and population equivalents from each WwTW. In contrast, isotopic ratios of δ 13 C and δ 34 S were unable to distinguish or quantify wastewater input into the rivers but differences were apparent amongst study streams. Overall, these results suggest that macroinvertebrate δ 15 N signatures can detect and quantify the effects of secondary sewage treatment inputs to riverine ecosystems. Moreover, the method potentially provides a sensitive means for tracing sewage-derived nutrients into food webs while inferring effects on aquatic communities where sewage-loads are subtle or confounded by other stressors.

Dietary analyses utilising visual methods to identify stomach and faecal contents have shown that urban red foxes (Vulpes vulpes) in Britain consume human‐derived (anthropogenic) food to varying degrees. Anthropogenic foods have been implicated in poor health outcomes for synanthropic species that consume them; therefore, it is important to examine the degree of such foods in the British fox diet. We analysed the carbon (δ13C) and nitrogen (δ15N) stable isotope ratios of whiskers collected from 93 foxes from across Britain to determine: (1) if stable isotope analysis (SIA) distinguished a difference in δ13C and δ15N between rural and urban foxes, and whether any difference was suggestive of anthropogenic food use; (2) the proportion of anthropogenic food consumption in urban foxes compared to rural foxes using a Bayesian mixing model; (3) whether sex, age or season of collection influenced fox diet as assessed by SIA, in relation to anthropogenic food use. We found the following: (1) urban fox diet was significantly different to rural foxes; urban foxes demonstrated significantly higher δ13C and lower δ15N, a pattern consistent with anthropogenic food consumption. (2) Food provided either directly or indirectly by humans contributed an estimated 34.6% of urban fox diet compared to approximately 6% of rural fox diet. (3) Across rural and urban foxes combined, there were significant isotopic differences between males and females, with females demonstrating higher δ13C. (4) No differences in δ13C and δ15N between subadults and adults were observed. (5) Season did not have a significant influence on δ13C and δ15N, despite winter demonstrating the highest δ13C and lowest δ15N seasonal means. Potential negative outcomes of anthropogenic food consumption are likely to disproportionately impact females more than males and urban‐dwelling foxes more than rural foxes. Anthropogenic food consumption has been implicated in poor health outcomes for synanthropes. We used stable isotope analysis on British red fox whiskers to show a distinct diet between rural and urban foxes, where rural and urban fox diets consisted of around 6% and 35% anthropogenic food, respectively. Additionally, females rather than males demonstrated isotopic patterns indicative of anthropogenic food use, suggesting that potential health risks from anthropogenic foods are more likely to impact female and urban‐dwelling foxes.

1. It has been known for some time that the consequences of 'decisions' made at one point in an animal's life may not always be borne immediately. For example, numerous studies have demonstrated the trade-off between current and future breeding success across multiple taxa. 2. It is becoming increasingly clear that such processes may also operate among seasons, such that the conditions experienced at one point in the annual cycle may have significant downstream impacts, or 'carry-over effects', and this is particularly evident among migratory species. We might therefore predict that certain combinations of reproductive and migratory strategy could lead to profound carry-over effects. However, the extent to which these phenomena might generate variation in fitness within a population is unclear. 3. Here, we investigate how winter habitat selection in a long-distance migrant, with extended parental care (the Light-bellied Brent goose) is influenced by parental status and how this has a counterintuitive effect on subsequent breeding success. 4. Dominant individuals and groups generally monopolize the best quality resources. In the case of geese, families are dominant; however, our findings highlight a hidden cost to raising a family. Stable isotope analysis demonstrates that later in the non-breeding season, adults with families utilize lower quality resources than non-breeders. This is probably caused by parents being constrained in habitat choice by the lower foraging efficiency of their juveniles. Consequently, parental adults end the winter in poorer condition than non-breeders. 5. We further demonstrate that parents in one year are less likely than expected to breed again in the next year and suggest that this is caused by conditions during the non-breeding period being carried over into the breeding season. In conclusion, we demonstrate previously hidden costs to raising a family, which are likely to be important in terms of life-history evolution.

Tool use is so rare in the animal kingdom that its evolutionary origins cannot be traced with comparative analyses. Valuable insights can be gained from investigating the ecological context and adaptive significance of tool use under contemporary conditions, but obtaining robust observational data is challenging. We assayed individual-level tool-use dependence in wild New Caledonian crows by analyzing stable isotope profiles of the birds' feathers, blood, and putative food sources. Bayesian diet-mixing models revealed that a substantial amount of the crows' protein and lipid intake comes from prey obtained with stick tools--wood-boring beetle larvae. Our calculations provide estimates of larva-intake rates and show that just a few larvae can satisfy a crow's daily energy requirements, highlighting the substantial rewards available to competent tool users.

Low volume resuscitation (LVR) in shock prevents deleterious effects of crystalloid loading in pre-hospital settings. Polyethylene glycol 20,000 (PEG-20k) based LVR solutions are 20-fold more effective at maintaining perfusion and survival in shock compared to conventional crystalloids. The aim of this study was to determine coagulation and platelet function of whole blood treated with 10% PEG-20k. Citrated blood from volunteers (n = 25) or early admission severely injured trauma patients (n = 9) were diluted 10% with various LVR solutions in a matched design with a paired volume control (saline), and studied using thromboelastography (TEG). In healthy volunteers and patients, 10% PEG-20k significantly increased clot amplification time (k), decreased propagation (angle), maximal clot size and strength (MA), and the overall coagulation index (CI), but not clot initiation (R) or fibrinolysis (Ly30), relative to paired saline dilutional controls. Clinically, K, angle, and MA were just outside of the normal limits in volunteers but not in patients. No statistical differences existed between PEG-20k and Hextend (HES) in either patient population. In a dose response series using volunteer blood, all effects of 10% PEG-20k on TEG were reversed and normalized by lower concentrations (7.5% and 5%). Furthermore, 7.5% PEG-20k produced similar resuscitation effects as 10% PEG in rodent hemorrhagic shock models (n = 5). In conclusion, PEG-20k based LVR solutions produced a dose-dependent minor hypocoagulative state, possibly associated with changes in clot propagation and platelet function, which can be reversed by dose reduction in concentration while providing superior LVR, microvascular rescue, and lactate clearance compared to saline or starch.

Novel crystalloid solutions containing polyethylene glycol polymers (PEG-20k) produce dramatic resuscitation effects but dose-dependently produce a hypocoagulative state. The objective of this study was to examine possible mechanisms of this effect. Based on previous thromboelastography data, we hypothesize the effect is largely due to platelet interactions with the polymers. Whole citrated blood from healthy volunteers was diluted ex-vivo 10% with crystalloids and tested for coagulation and platelet function. The specific tests included prothrombin time (PT), activated partial thromboplastin time (aPTT), fibrinogen and von Willebrand factor (vWf) activity, thrombin generation, thromboelastography with and without platelet mapping, platelet flow cytometry, and erythrocyte sedimentation rate. Fibrinogen and vWF activities, PT, and aPTT were not affected by PEG-20k dilutions. Thrombin activity was mildly suppressed with PEG-20k (TTP- 20%). Platelet mapping demonstrated significantly greater % inhibition of both ADP and arachidonic acid-induced platelet aggregation with PEG-20k, but direct ADP-activated gpIIa/IIIb (PAC1) and P-selectin (CD62P) binding site expression was not altered. Mild dose-dependent suppression of TEG-MA was seen with PEG-20k using platelet poor plasma. Erythrocyte Sedimentation Rates (ESR) were dramatically accelerated after dilution with 10% PEG-20k, which was competitively blocked by smaller PEG polymers, suggesting nonspecific PEG-20k cell binding effects. PEG-20k creates a mild hypocoagulative state in whole blood at concentrations ≥10%, which may be due to platelet-PEG interactions at the IIb/IIIa interface with lesser effects on fibrin polymerization. This interaction may cause a functional thrombasthenia induced by nonspecific platelet surface passivation by the PEG polymer.