Stable Nitrogen Isotope Analysis Research Articles

Small particles and heterotrophic protists support the mesopelagic zooplankton food web in the subarctic northeast Pacific Ocean

AbstractA quantitative understanding of the mesopelagic zooplankton food web is key to development of accurate carbon budgets and geochemical models in marine systems. Here we use compound specific nitrogen stable isotope analysis of amino acids to quantify the trophic structure of the microzooplankton and mesozooplankton community during summer in the subarctic northeast Pacific Ocean during the EXport Processes in the Ocean from Remote Sensing (EXPORTS) field campaign. Source amino acid values in particles and zooplankton provide strong evidence that basal resources for the mesopelagic zooplankton food web were primarily small (), suspended or slow‐sinking particles, but that surface organic matter delivered by vertically migrating zooplankton may have also been important. Comparisons of values of source and trophic amino acids provide estimates of food web length, which decrease significantly with depth and suggest that protistan microzooplankton are key components of the food web from the surface to at least 500. These results emphasize the importance of small particles as a source of carbon and nitrogen to mesopelagic communities in this region, support observations of an inverse relationship between zooplankton vertical migration and small particles as sources of carbon to deep‐sea food webs in low productivity environments, and document the role of heterotrophic protists as key trophic intermediaries in the mesopelagic zone at this location.

Diet and mobility in Late Antique Sicily: Isotopic data from the catacombs of Santa Lucia, Siracusa (Italy)

The catacombs of Santa Lucia were built during the 3rd century CE in Siracusa, Sicily, Italy, as a burial site for members of the local Christian community until the early 8th century CE. This site is an important cemeterial context of the Late Roman and Byzantine periods. The tombs and artifacts found suggest that individuals of varying wealth were buried in the catacombs. Historical accounts also confirm the presence of a significant Christian community from Syria and the Levant in Siracusa during this period. The objective of this research is to investigate the life histories of the Late Antique community interred in the catacombs using stable isotope analysis. This technique aimed to clarify the dietary differences between individuals of different social status and geographical origins, in order to re-evaluate the data from historical documents. To achieve this, we conducted stable carbon, nitrogen, and oxygen isotope analyses on skeletal samples from 25 individuals recovered from the catacombs of Santa Lucia, using established methods. The results revealed significant dietary diversity among the individuals buried in the catacombs, with evidence of the consumption of both C3 and C4 plants, as well as fish from both freshwater and sea sources.The oxygen isotopes show a particularly broad range in both the small sample set of bones and the larger set of teeth, suggesting a significant degree of mobility for most of the individuals tested. The high variability found in the diet and the evidence of mobility for most of the individuals tested not only between early age and adulthood, but also throughout their lives. It raises new questions and calls for the consideration of the archaeological and historical implications of these novel discoveries.

Specialist shorebird respond to prey and habitat availability through trophic plasticity

Spatiotemporal variations in food availability represent a challenge to the persistence of specialist species. The American oystercatcher (Haematopus palliatus) is a shorebird regarded as a bivalve specialist, although foraging habitats and prey species may vary along its distribution. Here, we studied American oystercatcher breeding in sites with variable landscapes to test the effect of temporal and spatial variations in food availability and dietary aspects. Between 2017 and 2021, we sampled oystercatchers (n = 100) and macroinvertebrates at the mesolitoral zone in five foraging areas in southern Brazil, three composed by sand and rock substrates (mixed), and two by sandy beach only. We obtained biological samples from oystercatchers and macroinvertebrates for carbon (δ13C) and nitrogen (δ15N) stable isotope analysis. In addition, we carried out systematic sampling of macroinvertebrates in sandy beaches at foraging areas to assess prey availability. Main findings showed the oystercatcher diet to be influenced both by the heterogeneity of foraging habitats and temporal fluctuations in availability of food resources. Bivalves contributed ∼60% to the diet of oystercatchers, but differences in the preferred bivalve species were detected among areas. In sites with mixed substrates, oystercatchers had a wider isotopic niche, suggesting habitat heterogeneity induced a more varied diet. Finally, we also observed interannual variation in the diet that may be associated with variation in macroinvertebrate availability on sandy beaches, especially for non-bivalve prey. Therefore, both temporal variations in food availability and foraging habitat heterogeneity seem to shape the foraging ecology of oystercatchers in the coastal zone, evidencing trophic plasticity in this specialist shorebird.

Trophic ecology of Angolan cold-water coral reefs (SE Atlantic) based on stable isotope analyses

Cold-water coral (CWC) reefs of the Angolan margin (SE Atlantic) are dominated by Desmophyllum pertusum and support a diverse community of associated fauna, despite hypoxic conditions. In this study, we use carbon and nitrogen stable isotope analyses (δ13C and δ15N) to decipher the trophic network of this relatively unknown CWC province. Although fresh phytodetritus is available to the reef, δ15N signatures indicate that CWCs (12.90 ± 1.00 ‰) sit two trophic levels above Suspended Particulate Organic Matter (SPOM) (4.23 ± 1.64 ‰) suggesting that CWCs are highly reliant on an intermediate food source, which may be zooplankton. Echinoderms and the polychaete Eunice norvegica occupy the same trophic guild, with high δ13C signatures (-14.00 ± 1.08 ‰) pointing to a predatory feeding behavior on CWCs and sponges, although detrital feeding on 13C enriched particles might also be important for this group. Sponges presented the highest δ15N values (20.20 ± 1.87 ‰), which could be due to the role of the sponge holobiont and bacterial food in driving intense nitrogen cycling processes in sponges’ tissue, helping to cope with the hypoxic conditions of the reef. Our study provides first insights to understand trophic interactions of CWC reefs under low-oxygen conditions.

Movement and population dispersal of dolphinfish (Coryphaena hippurus) across the Eastern Tropical Pacific inferred from carbon and nitrogen stable isotope analyses.

The dolphinfish (Coryphaena hippurus) is a globally distributed marine predator that supports one of the most important coastal fisheries along the Eastern Tropical Pacific (ETP), but its spatial movements in this area are poorly understood. Stable isotope values (δ13 C and δ15 N) of white muscle from dolphinfish (n = 220) captured at different locations across the ETP (i.e., Mexico, Costa Rica, Ecuador, Peru and oceanic areas) were normalized to copepod baseline stable isotope values to estimate dolphinfish trophic position, movements and population dispersal. Movement or residence patterns were inferred from the difference in δ15 N values (Δ15 Ndolphinfish-copepod ‰) between copepods and dolphinfish muscle. Baseline corrected isotope values (δ13 Cdolphinfish-copepod and δ15 Ndolphinfish-copepod ) of dolphinfish muscle were used to estimate isotopic niche metrics and infer population dispersal across isoscapes. Values of δ13 C and δ15 N differed between juvenile and adult dolphinfish and across the ETP. Trophic position estimates ranged from 3.1 to 6.0 with a mean of 4.6. Adults and juveniles had similar trophic position estimates, whereas isotopic niche areas (SEA ‰2 ) of adults were greater relative to juveniles in every location. Adult dolphinfish showed "moderate movement by some individuals" in all locations based on Δ15 Ndolphinfish-copepod values, except for Costa Rica where adults were classified with "high degree of movement by some individuals" whereas juveniles showed "limited movement" in all areas except Mexico. Population dispersal based on Δ15 Ndolphinfish-copepod values showed "moderate" and "high" dispersal for adults and "no dispersal" for most juveniles, except for Mexico. This study provides insight into potential dolphinfish spatial mobility across an area of interest for multiple nations, which can help to improve stock assessments and management of the species.

Forensic Discrimination of Smokeless Powders Using Carbon and Nitrogen Isotope Ratios.

Improvised explosive devices pose a threat to the public by way of terrorism and criminal activities. In the United States a commonly used low explosive in improvised explosive devices is smokeless powder (SP), due to its ease of access. Traditionally, forensic examinations are often sufficient in determining the physical and chemical characteristics of SPs. However, these exams are limited in differentiating or associating SPs when comparing two materials which are physically and/or chemically consistent. Stable isotope analysis of carbon and nitrogen has been used for explosives to further forensic chemical comparisons and aid in sample differentiation. In this manuscript we explore the utility of stable isotope analysis of SPs to differentiate manufacturer and geographic origin. Both bulk isotope analysis and component isotope analysis of carbon and nitrogen via an extraction method using dichloromethane were evaluated to compare the overall isotope signature of individual SPs. Through the combination of bulk and component isotope measurements of SPs, we were able to identify geographic relationships; however, the manufacturer origins were not as clearly discriminated. This technique demonstrates a potential improvement to traditional forensic examinations of smokeless powder by adding additional information when explosives are chemically and/or physically consistent.

Sources of contamination in sediments of retention tanks and the influence of precipitation type on the size of pollution load

Densification of cities and urban population contributes to increased runoff and suspended solids and alteration of the urban water cycle. Nowadays, Blue-Green Infrastructure is promoted to increase a city’s resilience to floods; however, stormwater drainage systems, supported with retention tanks are still important in protecting urban areas against floods. Sediment accumulation in stormwater infrastructure relates to an issue of pollutants such as heavy metals, nutrients etc. Research on the origin of the pollutants associated with the suspension and ultimately sediment accumulated in sewage can bring new insights about processes in urban catchment areas. This is the first study, which is focused on the analysis of stable carbon and nitrogen isotopes in bottom sediments collected from municipal retention tanks to verify the origin of the deposited pollutants immediately after pluvial floods. The research was additionally extended with water quality analyzes immediately after three types of weather: a dry period, typical precipitation (< 30 mm) and torrential rainfalls (2 events with daily precipitation over 30 mm which caused pluvial flooding of the city area). Analyses of sediments indicated that the main source of carbon and nitrogen in the bottom of the retention tanks had been brought with stormwater runoff from the city area. Organic nitrogen fertilizers appeared to be the main source of nitrogen, while the sources of organic carbon were mixed: C3 land plants, wood, and oil. Additionally, it was found that torrential rainfall caused a 23-fold increase of N-NO3 concentration, a sevenfold increase of P-PO4 concentration, and an over fivefold increase of concentration of organic matter, in comparison to typical precipitation.

D15N and d13C in skin biopsy samples: a note on their applicability for examining the relative trophic level in three rorqual species

Preliminary stable nitrogen and carbon isotope analysis was undertaken to investigate whether the resulting data support current knowledge of diet as obtained by conventional approaches. Blue (Balaenoptera musculus), fin (B. physalus) and Bryde’s (B. edeni) whales co-occur temporally and are known to feed in the Gulf of California, Mexico. Isotope measurements were taken from: known prey (three euphausiids and four sardine samples); skin biopsies (two for each whale species); and from faeces (one blue and three fin whale samples). Although the sample size was small, the range of d15N values obtained was consistent with prior knowledge of the whales feeding habits, with values increasing in the order: blue (x¯= 12.9), fin (x¯= 15.4) and Bryde’s whales (x¯= 15.8). The low value for the blue whale confirms its known stenophagous habit. The closeness of d15N values for fin and Bryde’s whales coincides with the known icthyophagous habits of the Bryde’s whale and the more generalist fin whale which feeds on both fish and zooplankton. The difference in d13C values for fin (x¯= 16.0) and Bryde’s whales (x¯= 18.1) suggests that although they feed at the same trophic level, they might use different food sources or feeding sites. Results of d15N suggest that fin and Bryde’s whales share the same relative trophic level, blue whales and juvenile sardines (S. sagax) share a lower position, followed by the euphausiid (Nematocelis difficilis) and fin whale faeces, and at the lowest level blue whale faeces.

Trophodynamics features and potential human health risk of arsenic and cadmium in marine fauna from the Yellow River Estuary, China

Toxic arsenic (As) and cadmium (Cd) pollution threatens organisms and humans in coastal ecosystems, but their biomagnification in marine systems remains under debate. This study investigated the levels and trophodynamic features of As and Cd, and potential human health risks of marine fauna within continuous trophic levels (TLs) from the Yellow River Estuary, China, and adjacent sea (YRE), as indicated by nitrogen stable isotope analyses. Individual faunal samples were grouped into continuous TL ranges and analyzed separately in fish and invertebrates. As and Cd concentrations varied significantly between fish and invertebrates within different TL ranges. Trophic magnification factors (TMFs) also revealed different bioaccumulation features of As and Cd with increasing TL via trophic transfer in the food chain. Although As and Cd were biodiluted in marine organisms overall from the YRE, they were biomagnified in invertebrates through trophic transfer, with TMFs of 1.91 and 1.70, respectively. As and Cd biomagnification in invertebrates was hidden by overall evaluation of toxic element bioaccumulation in marine fauna. Crustacea accounted for 55% of the invertebrate taxa in the study, which could have an important role in the biomagnification of these two elements in invertebrates as a whole. Given that marine organisms occupying higher trophic positions at higher risk of As and Cd biomagnification might be underestimated in the analyses of mean values at the species level, the target hazard quotient through fish and invertebrate consumption was calculated separately based on individuals distributed within continuous TL ranges corresponding to element concentrations, and the health risks to adults and children were evaluated. Results indicated that, in the study area, the non-carcinogenic health risk associated with As and Cd from consuming invertebrates was higher than that from fish, especially for children. In addition, estimation of As carcinogenic risk (>10–4 in both invertebrates and fish) also indicated that ingestion of seafood from the YRE with suggested meal size would cause cancer risk with long-term consumption, especially of invertebrates. Therefore, it is necessary to monitor toxic metal concentrations in aquatic organisms to devise regulations around seafood consumption by humans.

Investigating food web structure and system function of an artificial reef ecosystem based on carbon and nitrogen stable isotope analysis: implications for reef management

IntroductionFood web is an important basis for identifying trophodynamic processes, and evaluating the structural and functional characteristics of ecosystems. The trophodynamics and system function of artificial reef (AR) ecosystems have rarely been examined.MethodsStable isotope analysis was used to investigate the food web structure and functions of an artificial reef (AR) ecosystem in this study.Results and DiscussionThe δ13C and δ15N values of particulate organic matter (POM) in AR showed noticeable seasonal changes, and the δ13C value of POM in autumn was significantly higher than that in other seasons (p&amp;lt;0.05). There were no significant seasonal variations in the δ13C values of solid organic matter (SOM), and no significant difference between SOM and POM was observed except in autumn. Moreover, macroalgae did not significantly affect the δ13C values of SOM. Phytoplankton may be the primary nutrient source in the AR ecosystem. The δ13C values of most crustaceans in the AR were approximately between (-17.03 ± 0.22) ‰ – (-17.74 ± 0.07) ‰, higher than those of most fish, indicating that they may have different basal nutrient sources. The trophic level (TL) of invertebrates was between 2.00 and 3.09, and that of fish was between 2.98 and 3.66. The distribution of δ13C and TLs of crustaceans and fish showed that, except for crustaceans, bivalve shellfish and zooplankton might also be important food sources for fish in the AR ecosystem.ConclusionThe δ13C and δ15N values of most species in the AR showed good continuity, indicating that they may be mainly produced from the AR ecosystem. Migratory species such as Lateolabrax japonicus and Sepiella maindroni showed higher δ13C values, indicating that they may have migrated from other sea areas. To maintain the stability of the ecosystem structure and function of the AR ecosystem, fishing activities should be carried out following the maximum sustainable yield theory. Future research needs to identify the nutritional relationship between AR and its adjacent sea areas, to depict the food web structure of the AR with higher accuracy.

Isotopic niches of the Northern shoveler Spatula clypeata in spring migratory stopover sites in the Marais breton, France

ABSTRACT The Northern shoveler, Spatula clypeata, makes several migratory stopovers to reach its breeding site in the best conditions. These stopovers allow the species to replenish their reserves. Therefore, feeding efficiency at such sites is essential. Despite its importance, few studies have been conducted on the spring ecology of the shoveler, particularly on its diet at stopover sites. Therefore, this study focused on the Northern shoveler’s feeding habit during its spring migratory stopover in the Marais breton (MB), a wetland situated in Vendée (France, Atlantic coast). The shoveler’s plasma and potential food resources were studied using a stable carbon and nitrogen isotope analysis. The study showed that the shoveler feeds primarily on microcrustaceans, especially Cladocera and Copepoda; Chironomidae larvae, Corixidae, Hydrophilidae larvae, and particulate organic matter. This last food source, the POM, had never been highlighted before.

Determining the trophic transfer of metal(loid)s and arsenic speciation in freshwater aquatic organisms by quantifying diet compositions

Bioaccumulation through diet is the predominant source of metal(loid)s in fishes; however, the trophic transfer of metal(loid)s from the diet to aquatic organisms remains largely unclear. In this study, aquatic organisms and five potential food sources (leaf litter, coarse and fine particulate organic matter (CPOM and FPOM, respectively), epilithon and fish) were collected around the Shimen Realgar Mine of China. Stomach content analysis and stable nitrogen and carbon isotope analysis, combined with a new Bayesian mixing model (MixSIAR), were used to quantify diet compositions of aquatic organisms. The δ13C and δ15N values varied among fish sizes and sampling sites and were probably related to the diet shift of aquatic organisms. The MixSIAR modelling results showed that the aquatic organisms’ food sources were mainly composed of FPOM (9%–68%) and epilithon (15%–65%), with leaf litter, CPOM and fish accounting for smaller proportions (2%–30%). Concentrations ranged from 0.91 to 1298 mg/kg for As, 0.01–1.30 mg/kg for Cd, 0.12–37.79 mg/kg for Pb, 0.63–1158 mg/kg for Cr, 1.22–411 mg/kg for Cu, 0.82–1772 mg/kg for Mn, 0.31–542 mg/kg for Ni and 21.84–1414 mg/kg for Zn in all the collected samples, including the aquatic organisms and the relevant food sources. The metal(loid) concentrations in the CPOM, FPOM and epilithon were significantly higher than those in aquatic organisms and leaf litter. In addition, the biomagnification factors were all less than 1, indicating a biodilution from diet to freshwater organisms. The predominant As species were organic As in aquatic organisms, while inorganic As was common in their food sources, indicating that As biotransformation occurred within the freshwater food chain.

Trophic ecology of co-occurring fishes in the Sundays River Valley irrigation ponds, assessed using stable isotope and gut content analyses.

The analysis of food web structures has increased the understanding of the dynamics of organisms belonging to different trophic levels. In this study, the diet of two native species, Glossogobius callidus and Gilchristella aestuaria, was assessed in the presence of two non-native species, Oreochromis mossambicus and Gambusia affinis, in irrigation ponds, Eastern Cape Province, South Africa. The proportion of dietary items consumed and assimilated by the four fish species were inferred from gut contents and carbon and nitrogen stable isotope analysis. Stable isotope analysis revealed that both G. affinis and O. mossambicus had a larger isotopic niche size than G. callidus and G. aestuaria. Although G. callidus fed on benthic resources and G. aestuaria fed on phytoplankton, gut content analysis showed that G. callidus, O. mossambicus and G. affinis fed predominantly on benthic resources, whereas G. aestuaria fed mainly on plankton resources. Considerable niche overlap corroborates the view that resource competition is a major factor shaping the composition of the four fish species. This study highlighted the low diversity of the food web within the Sundays River Valley irrigation ponds, where food items are shared by all the small-bodied fishes.

Diving into the diet of provisioned smooth stingrays using stable isotope analysis.

Recreational fishing waste, produced from processing catches at shore-based fish cleaning facilities and discarded into adjacent waters, is foraged by various aquatic species. However, the potential alterations to the diet of consumers of these resources are poorly studied. Smooth stingrays (Bathytoshia brevicaudata) are a large demersal mesopredatory ray species and common scavenger of recreational fishing discards around southern Australia. Due to their attraction to fish cleaning sites, they are also common targets of unregulated 'stingray feeding' tourism where they are fed commercially produced baits (e.g., pilchards). This study provides a preliminary assessment of the diet of smooth stingrays provisioned recreational fishing discards and baits at two sites in southern New South Wales, Australia (Discard Site: recreational fishing discards only; Provisioning Site: recreational fishing discards and commercial baits) using stable isotope analysis of carbon (δ13 C) and nitrogen (δ15 N), and Bayesian stable isotope mixing models. Our results indicate that at both sites invertebrates, considered a main part of the natural diet of smooth stingrays, made a limited contribution to the diets of provisioned stingrays, while a benthic teleost fish that is a common recreational catch was the dominant contributor. As the assessed teleost is potentially a natural prey item for smooth stingrays, it remains unclear whether the contribution came from recreational fishing discards or natural foraging. However, due to smooth stingrays' typically opportunistic foraging strategy, we expected a greater mixture of resources from low to high trophic level prey than was observed. These results suggest that smooth stingrays have either lower reliance on invertebrates as a result of utilizing provisioned resources or higher reliance on teleost fishes than previously thought. Commercial bait products fed to stingrays at the Provisioning Site were not a major contributor to the diets of smooth stingrays, suggesting this activity has a low impact on their nutrition.

The subsistence economy in the Pingcheng area during the Northern Wei Dynasty: Stable isotope analysis of human bones obtained from the Datong Erzhong cemetery in Shanxi, China

Evidence indicates that diverse subsistence economies existed in the Pingcheng area (now Datong) during the Northern Wei Dynasty. This article details carbon and nitrogen stable isotope analyses conducted on human bones (n = 48) from the Datong Erzhong cemetery in Shanxi, China, to reveal the extent of agricultural factor development in diverse subsistence economies. The results show that, at the time, most humans (−10.4 ± 0.8 ‰, 9.7 ± 0.7 ‰, n = 40) primarily relied on millet-based foods. A few individuals (−14.7 ± 2.4 ‰, 10.9 ± 1.1 ‰, n = 8) lived on C3/C4 mixed food with abundant animal proteins. The isotope results of human and animal remains and charred millet obtained from nine contemporaneous cemeteries and/or sites indicate that millet-based agriculture was the dominant form of subsistence economy during the Pingcheng period (398–494 CE). Analysis of the proportion of millet-based food consumed by the individuals whose remains have been examined show that a dietary shift toward gradient millet consumption occurred in the Pingcheng area over time, indicating that millet agriculture became a dominant economic strategy.

Strong temporal variation of consumer δ13C value in an oligotrophic reservoir is related to water level fluctuation

Using stable carbon and nitrogen isotope analysis (δ13C and δ15N) to assess trophic interactions in freshwater ecosystems is a well established method, providing insight into ecosystem functioning. However, the spatial and temporal variability of isotope values, driven by environmental fluctuation is poorly understood and can complicate interpretations. We investigated how the temporal variation of stable isotopes in consumers (fish, crayfish and macrozoobenthos) of a canyon-shaped oligotrophic reservoir is associated with environmental factors such as water temperature, transparency, flooded area, and water quality measures. Consumers and their putative food sources were sampled and analyzed for carbon and nitrogen stable isotopes annually, and environmental parameters were measured monthly from 2014 to 2016. Results revealed significant differences in δ13C and δ15N values in each consumer among studied years. Over the years, fish and crayfish expressed differences in δ13C between 3 and 5‰, whereas in zoobenthos differences were 12‰. Variability in δ15N was similar across all consumers (2–4‰). Moreover, results suggest that the flooded area of the reservoir was a major driver of δ13C stable isotope values variation in consumers, while variation in δ15N was not linked to any of the studied environmental factors. Bayesian mixing models further showed significant changes in the origin of detritivorous zoobenthos carbon sources (reversal shift from terrestrial detritus to algae origin) between years with low water level to years with the standard water level. Other species showed only slight differences in food source utilization among years. Our study highlights the importance of environmental factors as sources of variation in consumer’s stable isotope values which should be considered especially when studied ecosystem strongly fluctuate in some environmental factor.

Dietary plasticity linked to divergent growth trajectories in a critically endangered sea turtle

Foraging habitat selection and diet quality are key factors that influence individual fitness and meta-population dynamics through effects on demographic rates. There is growing evidence that sea turtles exhibit regional differences in somatic growth linked to alternative dispersal patterns during the oceanic life stage. Yet, the role of habitat quality and diet in shaping somatic growth rates is poorly understood. Here, we evaluate whether diet variation is linked to regional growth variation in hawksbill sea turtles (Eretmochelys imbricata), which grow significantly slower in Texas, United States versus Florida, United States, through novel integrations of skeletal growth, gastrointestinal content (GI), and bulk tissue and amino acid (AA)-specific stable nitrogen (δ15N) and carbon (δ13C) isotope analyses. We also used AA δ15N ΣV values (heterotrophic bacterial re-synthesis index) and δ13C essential AA (δ13CEAA) fingerprinting to test assumptions about the energy sources fueling hawksbill food webs regionally. GI content analyses, framed within a global synthesis of hawksbill dietary plasticity, revealed that relatively fast-growing hawksbills stranded in Florida conformed with assumptions of extensive spongivory for this species. In contrast, relatively slow-growing hawksbills stranded in Texas consumed considerable amounts of non-sponge invertebrate prey and appear to forage higher in the food web as indicated by isotopic niche metrics and higher AA δ15N-based trophic position estimates internally indexed to baseline nitrogen isotope variation. However, regional differences in estimated trophic position may also be driven by unique isotope dynamics of sponge food webs. AA δ15N ΣV values and δ13CEAA fingerprinting indicated minimal bacterial re-synthesis of organic matter (ΣV &amp;lt; 2) and that eukaryotic microalgae were the primary energy source supporting hawksbill food webs. These findings run contrary to assumptions that hawksbill diets predominantly comprise high microbial abundance sponges expected to primarily derive energy from bacterial symbionts. Our findings suggest alternative foraging patterns could underlie regional variation in hawksbill growth rates, as divergence from typical sponge prey might correspond with increased energy expenditure and reduced foraging success or diet quality. As a result, differential dispersal patterns may infer substantial individual and population fitness costs and represent a previously unrecognized challenge to the persistence and recovery of this critically endangered species.

Deciphering the complex trophic relationship of the black-spotted croaker (Teleostei: Sciaenidae) and its parasites using stable isotope analysis

The stable isotope values of nitrogen (δ15N) and carbon (δ13C) have been widely used in ecological studies to decipher the trophic relationships and interactions that occur between living organisms. The aim of this study was to determine the trophic relationship between a commercially important tropical Australian marine fish ( Protonibea diacanthus (Lacepède, 1802)) (Sciaenidae) and its associated parasites, through stable isotope analysis of nitrogen and carbon (δ15N and δ13C). We examined the stable isotope ecology of four parasitic organisms: adult ectoparasitic copepods, and endoparasitic adult digeneans and nematodes and plerocercoids. Nitrogen in endoparasites was consistently depleted when compared with the host; however, digeneans expressed nitrogen signatures almost equivalent to those of the host. Ectoparasitic copepods were the only parasite that was substantially enriched in nitrogen compared with the host. All adult parasitic organisms were carbon depleted when compared with the host tissue associated with the site of infection; however, plerocercoids were enriched. Our findings emphasize the complexity of parasite–host interactions and the varying values of isotopic discrimination between parasite type, life-cycle stage, and location in host.

Variability in feeding habitats of red deer sensu lato in Eurasia in the Late Pleistocene and Holocene

Red deer (Cervus elaphus) is one of the species that is rather wide spread and survived across Europe over the Holocene. The analyses of carbon and nitrogen stable isotopes in bone collagen of ungulate remains have been applied in paleoecological studies as environmental and dietary indicators. In this study we present the carbon and nitrogen stable isotope compositions of previously radiocarbon-dated red deer bone samples (N = 68) found in Central, Southern and Eastern Europe and Asia and aligned to one of two species: European red deer (Cervus elaphus) and wapiti (Cervus canadensis). We showed that the values of carbon and nitrogen stable isotope ratios of European red deer and wapiti overlapped. Among all analysed independent factors (determined for the locality and time period relevant for each of the analysed samples), the variability of δ13C values in European red deer dated to the Holocene is best explained by forest cover and mean July temperature, and variability of δ15N values by the mean July temperature, annual precipitation and altitude. Additionally, combining the results of the present study with isotopic data on European red deer collected from published sources, we revealed that the values of δ13C and of δ15N in C. elaphus bones changed according to environmental oscillations that took place in Europe over the last 50 000 years. We concluded that red deer shifted their feeding habitats in relation to changing environmental conditions, for example, forest expansion during the climate warming, and in the mid to later Holocene in response to deforestation caused by human activity and the spread of agriculture. We also found out that red deer reacted in varied ways to changing local conditions in different regions of Europe. Modern individuals of C. elaphus had the lowest δ13C values among all analysed specimens, so they probably inhabited the most densely forested areas in comparison to other European red deer populations during the last 50 000 years.

Exploring the effects of weaning age on adult infectious disease mortality among 18th-19th century Italians.

The developmental origins of health and disease (DOHaD) hypothesis describes how early childhood stress affects morbidity and mortality later in life. The role of early childhood stress in mortality from infectious disease is understudied. Stressors in early childhood that weaken the immune system may result in increased susceptibility to infectious disease in adulthood. Weaning is one of the earliest potential periods of significant stress in early childhood. This research investigates the effect of weaning after ~6months of age on cholera mortality among 18th-19th-century Italian populations by determining if earlier breastfeeding cessation is associated with earlier mortality, analyzing childhood dietary variation and physiological stress markers, and determining if age-at-weaning completion differs between catastrophic and attritional populations. Serial dentin stable carbon and nitrogen isotope analyses from canines are compared between catastrophic (n=45) and attritional groups (n=23). Canines are sectioned serially from crown to apex, and the increment's δ15 N and δ13 C are used to estimate age-at-weaning completion. Catastrophic and attritional groups exhibit similar age-at-weaning completion (~2.8 years). Seventy-four percent of individuals lack elevated δ15 N values in dentin that formed during infancy. Age-at-weaning completion was not a predisposing factor in cholera mortality in adulthood in this sample. Age-at-weaning completion may not be significantly associated with infectious disease mortality because weaning completion likely occurred after infants had adapted to consuming contaminated weanling foods. Individuals without detectable weaning curves may represent infants who received supplementary foods since birth or were weaned before the age of 6-9months.