Dietary Carbon Research Articles

Assimilation of dietary nitrogen supplied by fish meal and microalgal biomass from Spirulina (Arthrospira platensis) and Nannochloropsis oculata in shrimp Litopenaeus vannamei fed compound diets

The biomass of several microalgae species represents one of many single cell-derived products with great potential as dietary ingredients for the aquaculture feed industry. The present study compares the assimilation of dietary nitrogen and total dry matter supplied by fish meal and biomass from Spirulina (Arthrospira platensis) and Nannochloropsis oculata in postlarval Pacific white shrimp, Litopenaeus vannamei. The natural isotopic signatures of the ingredients were used as biomarkers to assess their respective nutritional contributions. Three control diets were manufactured with each of the main ingredients to establish shrimps’ isotopic control values (initial mean weight 51 mg). Four mixed diets were formulated with varying proportions of ingredients on a dietary nitrogen basis (33:33:33 and permutated 50:25:25 proportions). Diets were supplied ad libitum four times daily for 22 days. Shrimp reared under most dietary treatments showed high growth rates. Final mean weight was significantly higher (268 ± 64 mg) in shrimp grown under diets containing only fish meal and those formulated with 50% fish meal (239 ± 64 mg) and 50% Spirulina (234 ± 57 mg). Isotopic assessments of ingredients and shrimp indicated significantly different nutrient assimilations. A higher incorporation of dietary nitrogen (43 to 52%) and dietary carbon (44 to 57%) from Spirulina was observed, while N. oculata and fish meal supplied lower proportions of dietary nitrogen to shrimp growth (4 to 33% and 25 to 51%, respectively). Results indicate a fast digestion and assimilation of Spirulina-derived nutrients, while N. oculata did perform poorly as a fish meal replacement ingredient.

Otolith δ13C values as a metabolic proxy: approaches and mechanical underpinnings

Knowledge of metabolic costs associated with maintenance, foraging, activity and growth under natural conditions is important for understanding fish behaviours and the bioenergetic consequences of a changing environment. Fish performance in the wild and within a complex environment can be investigated by analysing individual-level field metabolic rate and, at present, the natural stable carbon isotope tracer in otoliths offers the possibility to reconstruct field metabolic rate. The isotopic composition of carbon in fish otoliths is linked to oxygen consumption through metabolic oxidation of dietary carbon. The proportion of metabolically derived carbon can be estimated with knowledge of δ13C values of diet and dissolved inorganic carbon in the water. Over the past 10 years, new techniques to study fish ecology have been developed, and these can be used to strengthen the application of otolith δ13C values as a metabolic proxy. Here, we illustrate the great potential of the otolith δ13C metabolic proxy in combination with other valuable and well-established approaches. The novel approach of the otolith δ13C metabolic proxy allows us to track the effects of ontogenetic and environmental drivers on individual fish physiology, and removes a major obstacle to understanding and predicting the performance of free-ranging wild fish.

Natural 13C abundance reveals age of dietary carbon sources in nematode trophic groups

We determined the 13C/12C ratio (expressed as δ13C ‰) of microbial biomass and nematode trophic groups in a small-plot field experiment with soil converted from C3- to C4-crop (silage maize) 20 years ago. During this period, the plots were subjected to three different organic input treatments: 1) maize stubbles and roots left after harvest (MS), 2) MS plus annual addition of aboveground maize biomass (MS + B), and 3) MS plus annual addition of faeces from sheep fed exclusively with maize (MS + F). The different δ13C value of C3- and C4-crops allowed us to distinguish between old (>20 years old) C3-derived C and recent (<20 years old) C4-derived C incorporated into microbial biomass and nematodes.The δ13C value of phytophagous nematodes closely matched that of the maize. Bacterivorous nematodes had higher δ13C values than fungivorous nematodes and microbial biomass indicating that the C sources of bacterivorous nematodes are more recent than those of fungivorous nematodes and microbial biomass. At low abundance of fungivorous nematodes (MS and MS + F), the microbial biomass had higher δ13C values than the fungivorous nematodes, whereas their δ13C values were comparable at higher densities of fungivorous nematodes (MS + B). The higher C4-derived input in MS + F and MS + B treatments increased the δ13C values of bacterivorous nematodes and microbial biomass.In MS and MS + B treatments, recent C4-derived C accounted for 50 and 70% of microbial biomass-C, respectively. Corresponding values for fungivorous and bacterivorous nematodes were 30 and 75%, and 65 and 85%, respectively.We conclude that fungal-based decomposition pathways contribute more to the turnover of old soil C than bacterial-based decomposition. A substantial fraction of the microbial biomass and fungivorous nematode C in the MS treatment (50 and 70%, respectively) was C deposited in the soil more than 20 years ago, confirming that decade-old SOC remains biologically active.

The monogenean Paradiplozoon ichthyoxanthon behaves like a micropredator on two of its hosts, as indicated by stable isotopes.

The analysis of stable isotopes of carbon and nitrogen has been used as a fingerprint for understanding the trophic interactions of organisms. Most of these studies have been applied to free-living organisms, while parasites have largely been neglected. Studies dealing with parasites so far have assessed the carbon and nitrogen signatures in endoparasites or ectoparasites of different hosts, without showing general trends concerning the nutritional relationships within host-parasite associations. Moreover, in most cases such systems involved a single host and parasite species. The present study is therefore the first to detail the trophic interactions of a freshwater monogenean-host model using δ13C and δ15N, where a single monogenean species infects two distinctly different hosts. Host fishes, Labeobarbus aeneus and Labeobarbus kimberleyensis from the Vaal Dam, South Africa, were assessed for the monogenean parasite Paradiplozoon ichthyoxanthon, individuals of which were removed from the gills of the hosts. The parasites and host muscle samples were analysed for signatures of δ13C and δ15N using an elemental analyser connected to an isotope ratio mass spectrometer. Host fish appear to use partly different food sources, with L. aeneus having slightly elevated δ13C signatures compared to L. kimberleyensis, and showed only small differences with regard to their nitrogen signatures, suggesting that both species range on the same trophic level. Carbon and nitrogen signatures in P. ichthyoxanthon showed that the parasites mirrored the small differences in dietary carbon sources of the host but, according to δ15N signatures, the parasite ranged on a higher trophic level than the hosts. This relationship resembles predator-prey relationships and therefore suggests that P. ichthyoxanthon might act as a micropredator, similar to blood-sucking arthropods such as mites and fleas.

A neglected predictor of environmental damage: The ecological paw print and carbon emissions of food consumption by companion dogs and cats in China

Abstract Food consumption has considerable impacts on the environment. Recently, increasing numbers of companion animal owners feed their animals with high nutritional food, which requires much land space and has great impacts on carbon emissions. Therefore, the environmental impacts of food consumption by companion animals can be significant, especially in a country with a large companion animal population, like China. In the present study, the ecological indicators of the ecological paw print (EPP), carbon emission and energy consumption have been introduced for the first time to quantify the environmental impacts of food consumption by companion dogs and cats in China. Our results showed that the dietary EPP and carbon emissions of an average-sized dog relying on commercial dry food (0.82–4.20 ha year−1 and 0.037–0.190 ton. year−1) were ca. eight and three times higher than those of the dog relying on human leftover food (0.11–0.53 ha year−1 and 0.014–0.064 ton. year−1). There were more than 27.4 million companion dogs and 58.1 million companion cats in China in 2015. Assuming all these dogs and cats eat commercial dry food, the dietary EPP of the total dogs and cats was 43.6–151.9 million ha. year−1, which was equivalent to the dietary ecological footprint (EF) of 5.1%–17.8% (70.3–245.0 million) of Chinese people in 2015. The annual food consumption of all these dogs and cats was responsible for up to 2.4–7.5 million tons carbon emissions, which was equivalent to the entire carbon emissions of 2.5%–7.8% (34.3–107.1 million) of Chinese people in terms of food consumption in 2015. Our results also demonstrated that some companion animals (especially large dogs) consumed more food energy than their actual needs to keep normal activity, which resulted in food waste and exacerbated the environmental burden. This research develops an accurate method for companion animals' dietary EPP calculation and quantifies the significant environmental impacts by investigating their dietary carbon emissions and energy consumptions. Findings from this study will motivate companion animal owners to reconsider the feeding regimens and husbandry activities, improve owners and even the whole Chinese people's awareness of sustainability, and ultimately promote the whole country's sustainable development.

Dietary seasonal variations in the Medieval Nubian population of Kulubnarti as indicated by the stable isotope composition of hair

ObjectivesThe island of Kulubnarti is located in Sudanese Nubia and contains two cemeteries, named R and S, which are dated to AD 550–800. In order to provide more detailed dietary information for this population and examine seasonality of diet, we analyzed the carbon isotope composition of hair samples from both cemeteries. Materials and methodsForty seven separate hair samples from 8 adults, 29 adolescents, 7 infants and 3 individuals with unknown age were analyzed. Long hair samples were cut transversely and divided into 2 cm longitudinal segments, to examine temporal variations in the dietary carbon sources. ResultsThe average carbon isotope value for the whole population was −17.95‰ (SD = 1.8). A significant difference between the two cemeteries was found with variances in the amount of C4 dietary carbon sources consumed. DiscussionThe results of hair isotope compositions concur with previous soft tissue investigations of Kulubnarti population which suggested that the dietary regimen contains a mix of C3 and C4 plant-based sources. A seasonal variation in diet can be inferred from the sequential hair segments of Kulubnarti individuals. These suggest a dietary transition between dominant C3 plant-based sources in winter to dominant C4 ones in summer with a small contribution of the non-harvested, alternative, crop.

Capturing Roman dietary variability in the catastrophic death assemblage at Herculaneum

Here we present a comparative study of stable carbon (δ13C) and nitrogen (δ15N) isotope data from 81 individuals from the catastrophic death assemblage at Herculaneum (79CE) and compare these with the attritional sites of Velia (Salerno, Italy, 1st–2ndcenturyCE) and Isola Sacra (Rome, Italy, 1st–2ndcenturyAD). The instantaneous deposition of the Herculaneum assemblage highlights some interesting differences in our contextual and methodological understanding of stable dietary isotopes, suggesting that isotopic variation between sites may sometimes be a result of greater temporal variability rather than truly comparable differences. Our results suggest that the people of Herculaneum obtained a relatively small proportion (ca. 30%) of their dietary carbon from marine foods; the majority originating from terrestrial foodstuffs of a similar carbon isotopic composition, most likely cereals. Also observed is a generally greater dietary isotopic enrichment in male individuals than females. We infer that males had greater access to fish which may be reflective, in part, of the sociodemographic framework characteristic of Roman society. Finally, we highlight the methodological challenges which may be faced when undertaking comparisons of δ13C and δ15N data between the various age-related strata of a population, particularly due to the slow and variable rate of collagen turnover.

Does diet intervention in line with nutrition recommendations affect dietary carbon footprint? Results from a weight loss trial among lactating women.

Results from studies evaluating the sustainability of diets combining environmental and nutritional aspects have been diverse; thus, greenhouse gas emissions (that is, carbon footprint (CF)) of diets in line with dietary recommendations in free-living individuals warrants further examination. Here, changes in dietary CF related to changes in food choice during a weight loss trial among lactating women who received a 12-week diet intervention based on the Nordic Nutrition Recommendations (NNR) 2004 were analyzed. The objective of this study was to examine if a diet intervention based on NNR 2004 results in reduced dietary CF. Changes in dietary CF were analyzed among 61 lactating women participating in a weight loss trial. Food intake data from 4-day weighed diet records and results from life cycle analyses were used to examine changes in dietary CF across eight food groups during the intervention, specified in the unit carbon dioxide equivalent (CO2eq/day). Differences in changes in dietary CF between women receiving diet treatment (D-group) and women not receiving it (ND-group) were compared. There was no difference in change in dietary CF of the overall diet between D- and ND-group (P>0.05). As for the eight food groups, D-group increased their dietary CF from fruit and vegetables (+0.06±0.13 kg CO2eq/day) compared with a decrease in ND-group (-0.01±0.01 kg CO2eq/day) during the intervention, P=0.01. A diet intervention in line with NNR 2004 produced clinically relevant weight loss, but did not reduce dietary CF among lactating women with overweight and obesity. Dietary interventions especially designed to decrease dietary CF and their coherence with dietary recommendations need further exploration.

Ontogenetic changes in dietary carbon sources and trophic position of two co-occurring horseshoe crab species in southwestern China

Ontogenetic changes in dietary carbon sources and trophic position of two co-occurring horseshoe crab species in southwestern China

Aquatic food‐web structure along a salinized dryland river

Summary Very little is known about the ecosystem impacts of river salinization despite expectations for global increases in salinization with growing water demand and climate change. In some rivers in the southwestern United States, salinization has occurred as a result of natural saline inputs exacerbated by flow alteration and other anthropogenic impacts. Salinization in the Pecos River has been linked to declines in fish diversity, but impacts on the structure of aquatic food webs have not been investigated. We assessed variation in local food webs along the longitudinal gradient of the main stem Pecos River by estimating carbon sources, trophic positions and assemblage‐wide trophic structure for aquatic consumers at 12 sites using stable isotope analysis (δ13C and δ15N). Temporal variation across seasons was also examined for common fish species at a subset of sites. Consumer richness, food‐chain length and assemblage‐wide niche breadth were inversely related to specific conductivity. Mixing models revealed differences in sources of dietary carbon supporting fish production along the longitudinal fluvial gradient, with a shift towards reliance on algal production in the salinized reaches of the river. Trophic niche breadth was greatest for assemblages in less degraded sites with higher fish species richness. Local food webs in salinized sites were dominated by euryhaline species and had shorter food chains and narrower assemblage‐wide niche breadths. Across seasons, δ13C and δ15N signatures remained fairly constant for five common fish species. Our results suggest that salinization in portions of the Pecos River constrains the diversity of consumers and trophic resources in local food webs. Characterising changes in food‐web structure in relation to salinization and other environmental changes is important for habitat assessment, stream restoration and other conservation strategies.

Daphnia magna fitness during low food supply under different water temperature and brownification scenarios

&lt;p class="BodyA"&gt;Much of our current knowledge about non-limiting dietary carbon supply for herbivorous zooplankton is based on experimental evidence and typically conducted at ~1 mg C L&lt;sup&gt;-1&lt;/sup&gt; and ~20°C. Here we ask how low supply of dietary carbon affects somatic growth, reproduction, and survival of &lt;em&gt;Daphnia magna&lt;/em&gt; and test effects of higher water temperature (+3 °C relative to ambient) and brownification (3X higher than natural water color; both predicted effects of climate change) during fall cooling. We predicted that even at very low carbon supply (~5µg C L&lt;sup&gt;-1&lt;/sup&gt;), higher water temperature and brownification will allow &lt;em&gt;D. magna&lt;/em&gt; to increase its fitness. Neonates (&amp;lt;24 h old) were incubated with lake seston for 4 weeks (October-November 2013) in experimental bottles submerged in outdoor mesocosms to explore effects of warmer and darker water. Higher temperature and brownification did not significantly affect food quality, as assessed by its fatty acid composition. &lt;em&gt;Daphnia&lt;/em&gt; exposed to both increased temperature and brownification had highest somatic growth and were the only that reproduced, and higher temperature caused the highest &lt;em&gt;Daphnia&lt;/em&gt; survival success. These results suggest that even under low temperature and thus lower physiological activity, low food quantity is more important than its quality for &lt;em&gt;D. magna&lt;/em&gt; fitness.&lt;/p&gt;

Ontogenetic shifts in the diets of juvenile Chinook Salmon: new insight from stable isotopes and fatty acids

Variations in marine prey availability and nutritional quality can affect juvenile salmon growth and survival during early ocean residence. Salmon growth, and hence survival, may be related to the onset of piscivory, but there is limited knowledge on the interplay between the prey field, environment, and salmon ontogeny. Subyearling Chinook Salmon (Oncorhynchus tshawytscha) and their potential prey were sampled in coastal waters off Willapa Bay, USA to explore this issue. Three seasonal prey assemblages were identified, occurring in spring (May), early summer (June – July), and late summer (August – September). The onset of piscivory, based on salmon stomach contents, fatty acids, and stable isotopes occurred later in 2011 compared to 2012, and coincided with the appearance of Northern Anchovy (Engraulis mordax). Salmon fork length (FL) and carbon isotope values (δ13C) increased with a fatty acid biomarker for marine phytoplankton and decreased with a freshwater marker, indicating dietary carbon sources changed as salmon emigrated from the Columbia River. Salmon FL also increased with nitrogen isotope ratios (δ15N), trophic position, and a fatty acid marker for piscivory – a consequence of the ontogenetic shift in diet to fish. Salmon grew faster and obtained larger size and condition by September 2011 compared to 2012, which was related to inter-annual differences in ocean conditions and the duration over which Northern Anchovy were available. Our results support the idea that juvenile salmon growth depends on the onset and duration of piscivory, suggesting both of these factors may be important components of lifetime growth and fitness.

Use of feathers to assess polychlorinated biphenyl and organochlorine pesticide exposure in top predatory bird species of Pakistan

Little is known about the levels of organochlorines (OCs) in predatory bird species from Asia or the factors governing their concentrations. This study is the first report on concentrations of polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) in predatory birds of Pakistan. The concentrations of PCBs and OCPs were investigated using tail feathers of ten different species of predatory birds. In addition, concentration differences among body, tail, primary and secondary feathers were investigated for six individuals of black kite (Milvus migrans). Ranges of concentrations were highest for dichlorodiphenyldichloroethylene (p,p′-DDE: 0.11–2163ngg−1 dry wt.) followed by dichlorodiphenyltrichloroethane (p,p′-DDT: 0.36–345ngg−1 dry wt.), hexachlorobenzene (HCB: 0.02–34ngg−1 dry wt.), ∑PCBs (0.03–16ngg−1 dry wt.) and trans-nonachlor (TN; 0.01–0.13ngg−1 dry wt.). CB 118, 153, 138, and 180 along with p,p′-DDE were found as the most prevalent compounds. ∑PCBs and ∑DDTs were significantly different among species (both p<0.01) and omnivorous, scavengers, carnivorous and piscivorous trophic guilds (all p<0.03). Only ∑PCBs were significantly differentamong different families of birds (p<0.01). Values of stable isotopes (δ13C and δ15N) differed significantly (all p<0.01) among species, families, trophic guilds as well as terrestrial and aquatic habitat but not between nocturnal and diurnal predators (p=0.22 for δ13C; p=0.50 for δ15N). Concentrations of ∑PCBs, ∑DDTs and trans-nonachlor, but not HCB (p=0.86), were significantly different among different feather types (all p<0.01). Trophic and taxonomic affiliation as well as dietary carbon sources (δ13C) for species were identified as the variables best explaining the observed variation in exposure to the studied compounds. The significance of contributing factors responsible for OC contamination differences in predatory birds should be further elucidated in future studies.

Dietary single-walled carbon nanotubes promote early fecundity in Drosophila: Regulation of oogenesis via nutrition, akt activation and hormone

Dietary single-walled carbon nanotubes promote early fecundity in Drosophila: Regulation of oogenesis via nutrition, akt activation and hormone

Diet and gill morphology of the East Coast redeye round herring Etrumeus wongratanai off KwaZulu-Natal, South Africa

Stomach content analyses and measurements of gillraker morphology were used to assess the diet and feeding ecology of the East Coast redeye round herring Etrumeus wongratanai and provide data for comparisons with other small pelagic fishes off South Africa. Samples were collected by jigging from a kayak off Scottburgh, KwaZulu-Natal (KZN), over the period July 2013–May 2014. In total, 66 stomachs (containing 4 407 prey items) and 66 gill arches were examined. Stomach content analyses indicated that East Coast redeye round herring, at the time of sampling, fed on large (1 500–2 500 µm) particles, with ∼2 500 µm particles making the greatest contribution to dietary carbon. The species feeds on larger particles than do anchovy Engraulis encrasicolus and sardine Sardinops sagax, but on particles of a similar size to those consumed by West Coast redeye round herring Etrumeus whiteheadi. There were significant differences in mean gillraker gaps between East Coast redeye round herring and both sardine and anchovy, but not between East Coast and West Coast redeye round herring. The differences in gillraker gaps between East Coast redeye round herring, sardine and anchovy are indicative of resource partitioning through differential feeding, based on zooplankton size. The data suggest that there is no resource partitioning between East and West coast redeye round herring, indicating that competition is likely to occur between them. However, such competition is minimised by limited spatial overlap between these two species.

A Simple(R) Model to Predict the Source of Dietary Carbon in Individual Consumers

Quantitative individual human diet reconstruction using isotopic data and a Bayesian approach typically requires the inclusion of several model parameters, such as individual isotopic data, isotopic and macronutrient composition of food groups, diet-to-tissue isotopic offsets and dietary routing. In an archaeological context, sparse data may hamper a widespread application of such models. However, simpler models may be proposed to address specific archaeological questions. As a consequence of the intake of marine foods, individuals from the first century ad Roman site of Herculaneum showed well-defined bone collagen radiocarbon age offsets from the expected terrestrial value. Taking as reference these radiocarbon offsets and using as model input stable isotope data (δ13C and δ15N), the performance of two Bayesian mixing model instances (routed and concentration-dependent model versus non-routed and concentration-independent) was compared to predict the carbon contribution of marine foods to bone collagen. Predictions generated by both models were in good agreement with observed values. The model with higher complexity showed only a slightly better performance in terms of accuracy and precision. This demonstrates that under similar circumstances, a simple Bayesian approach can be applied to quantify the carbon contribution of marine foods to human bone collagen.

Adenosine signaling and the energetic costs of induced immunity.

Life history theory predicts that trait evolution should be constrained by competing physiological demands on an organism. Immune defense provides a classic example in which immune responses are presumed to be costly and therefore come at the expense of other traits related to fitness. One strategy for mitigating the costs of expensive traits is to render them inducible, such that the cost is paid only when the trait is utilized. In the current issue of PLOS Biology, Bajgar and colleagues elegantly demonstrate the energetic and life history cost of the immune response that Drosophila melanogaster larvae induce after infection by the parasitoid wasp Leptopilina boulardi. These authors show that infection-induced proliferation of defensive blood cells commands a diversion of dietary carbon away from somatic growth and development, with simple sugars instead being shunted to the hematopoetic organ for rapid conversion into the raw energy required for cell proliferation. This metabolic shift results in a 15% delay in the development of the infected larva and is mediated by adenosine signaling between the hematopoietic organ and the central metabolic control organ of the host fly. The adenosine signal thus allows D. melanogaster to rapidly marshal the energy needed for effective defense and to pay the cost of immunity only when infected.

Stable Isotope Record of Human and Sheep Enamel Carbonate from the Ancient Middle Euphrates Valley (Syria)

AbstractStable isotope analyses of human tooth enamel have allowed us to reconstruct the isotope composition of dietary carbon, changes in the oxygen isotope composition of drinking water and the possible migration of humans in ancient Terqa and Tell Masaikh (SE Syria). δ18Ocarbonate values of human tooth enamel from the interval comprising the Neo‐Assyrian to the modern Islamic periods (from 900 BC to AD 1949) generally mirror the isotope composition of Euphrates water, which is believed to have been a major drinking water source. Lower δ18Ocarbonate values of human Bronze Age apatite are linked to a different hydrologic system that was present in the Middle Euphrates valley at that time (2650–1700 BC). Higher δ18Ocarbonate values of some individuals in the Neo‐Assyrian (900–700 BC) and Islamic periods (AD 600–1200) may indicate human migration from the interior of the Near East. Low δ13Ccarbonate values (−11.3 to −12.4‰) of human tooth enamel from the interval comprising the Early Bronze to the Islamic periods (from 2650 BC to AD 1200) indicate C3 plants as a predominant source of dietary carbon. Changes in human dietary customs in SE Syria (with inferred usage of C4 plants) occurred in the modern Islamic period only (AD 1850–1949).Oxygen and carbon isotope data of sheep enamel show the usage of water bodies characterised by an enhanced evaporation rate during the Neo‐Assyrian time (900–700 BC) and grazing sheep herds on drier areas during the Islamic and the modern Islamic periods (after AD 600). Copyright © 2015 John Wiley &amp; Sons, Ltd.

Paleodiet in the Paracas Necropolis of Wari Kayan: carbon and nitrogen isotope analysis of keratin samples from the south coast of Peru

Despite being one of the most famous archaeological cemeteries in Peru, many questions remain about the people who were buried at the Paracas Necropolis of Wari Kayan, which was first excavated by Julio C. Tello in 1925. Here, we use bioarchaeology and biogeochemistry to elucidate the lives of individuals buried at Wari Kayan. More specifically, we present 90 new δ13Ckeratin and δ15Nkeratin values from 14 individuals buried at Wari Kayan and two artifacts made of human hair (mean δ13Ckeratin (VPDB) = −15.3 ± 0.9‰ (1σ, n = 90) and mean δ15Nkeratin (AIR) = +15.5 ± 1.2‰ (1σ, n = 90)). We interpret these light stable isotope data from archaeological human hair samples from the Paracas Necropolis of Wari Kayan as evidence for a mixed diet of C4 and C3 foods as dietary carbon sources and marine products as dietary nitrogen sources. Sequential hair samples from the same individuals do not exhibit large isotopic differences in hair that formed at different times before death. In addition to elucidating paleodiet at this important site, we interpret sequential isotopic hair data as evidence of a population whose diet was predominately coastal in the last weeks or months of life, either remaining on the coast or consuming coastal products in the highlands. These data elucidate paleodiet as well as the utility of applying newer isotopic methods to archaeological human remains from older museum collections to gain a better understanding of the past.

Examining the utility of bulk otolith δ13C to describe diet in wild-caught black rockfish Sebastes melanops

Otolith carbon isotope δ13C values may provide temporally resolved diet proxies in fish. If otolith δ13C values reflect diet, isotope values from recent otolith and muscle tissue should correlate and known ontogenetic diet shifts should be reflected in comparisons between otolith material deposited during different life history stages. We analyzed paired otolith and muscle samples for δ13C from black rockfish Sebastes melanops to examine the potential of otoliths to reflect diet in small (200−299 mm fork length) and large (≥300 mm) fish. We found a significant positive regression between δ13C values from recent (~12 mo) otolith material and muscle in large fish, but not in small fish. Within individual otoliths, δ13C values were enriched by ~3‰ in recent otolith edge material compared to age-0 otolith core material and were consistent with known nearshore−offshore gradients in δ13C values at the base of the food web. Bulk otolith δ13C appeared to provide a broad indicator of dietary carbon sources, but variation in metabolism and dissolved inorganic carbon δ13C among and within individuals likely influences otolith δ13C as well and limits precision. Nevertheless, the results are promising and bulk otolith δ13C may be an appropriate tool to examine large trophic and ecosystem level shifts that have occurred concurrently with changes in habitat, commercial fishing, invasive species, climate change, and other direct or indirect human impacts using historic or ancient otoliths. Future studies should continue to consider the utility of bulk otolith δ13C to describe diet in other marine fish using this simple approach.