Ecotoxicology of mercury concentrations in arctic lamprey (Lethenteron camtschaticum).

Arctic lamprey (Lethenteron camtschaticum) is an important dietary resource for rural and indigenous communities in parts of Alaska, with some commercial use. As with many fish species harvested for human consumption, there are concerns regarding mercury concentrations ([Hg]) in Arctic lamprey that may impact human health. To date, information regarding the life cycle and diet of Arctic lamprey is scarce, with no published studies examining [Hg] in Arctic lamprey tissues. Our goals were to investigate the feeding ecology of Arctic lamprey from the Bering Sea, determine how diet and potential dietary shifts might influence [Hg] in muscle, and determine if current [Hg] may pose a human health risk. The mean total [Hg] in Arctic lamprey muscle (n = 98) was 19 ng/g wet-weight. Log transformed total [Hg] were not associated with any measured biological variables including length, mass, δ13C values, or δ15N values. A stable isotope mixing model estimated that capelin (Mallotus villosus) accounted for 40.0 ± 4.0% of the Arctic lamprey diet, while Pacific sand lance (Ammodytes hexapterus) and Pacific herring (Clupea pallasii) accounted for 37.8 ± 3.1% and 22.2 ± 3.5% respectively. Finally, diet percentage compositions shifted based on size class (i.e., medium versus large). These results indicated that feeding location, bioaccumulation, and biomagnification are not important drivers of [Hg] in Arctic lamprey and current [Hg] do not pose a human health risk. Taken together, this research further expands our knowledge of Arctic lamprey trophic ecology in the eastern Bering Sea.

Mapping carbon and nitrogen isotopic composition of fingernails to demonstrate a rural-urban nutrition transition in the Center-West, Northeast, and Amazon regions of Brazil.

OBJECTIVE: The main objective of this study is to investigate diet patterns among rural and urban populations of the Center-West, Northeast, and Amazon regions of Brazil through the carbon and nitrogen isotopic composition of fingernails, recognizing that the extent of market integration is a key driver of food consumption. MATERIALS AND METHODS: In the Center-West, Northeast, and Amazon regions of Brazil, fingernails were sampled in clusters encompassing a major city, town, and rural village. A total of 2,133 fingernails were analyzed. Fingernails were clipped by donors using fingernail clippers. In the laboratory, samples were cleaned then weighed in small tin capsules before being isotopically analyzed for carbon and nitrogen. RESULTS: The overall mean δ13 C and δ15 N were -19.7 ± 2.8‰ and 10.6 ± 1.1‰, respectively. In the more remote villages, where access to food markets is more challenging, lower δ13 C prevails, suggesting that Brazilian staple foods (rice, beans, and farinha) still dominate. In areas with easier access to food markets, δ13 C values were higher, suggesting a change to a diet based on C4 plants, typical of a Brazilian supermarket diet. The variability among inhabitants in the same location expressed by a significant inverse correlation between δ13 C and δ15 N fingernail values suggested that "market integration" does not affect everyone equally in each community. DISCUSSION AND CONCLUSION: The nutrition transition has not yet reached some remote villages in these regions of Brazil or that the nutrition transition has not yet reached all residents of these remote villages. On the other hand, in several villages there is a considerable adherence to the supermarket diet or that some residents of these villages are already favoring processed food.

Reconstruction of human subsistence and husbandry strategies from the Iberian Early Neolithic: A stable isotope approach.

OBJECTIVES: The Early Neolithic involved an important social and economic shift that can be tested not only with the material culture, but also through biomolecular approaches. The Iberian Peninsula presents few Early Neolithic sites where fauna and humans can be analyzed together from an isotopic perspective. Here we present an isotopic study on the site of Cueva de Chaves as an example for understanding the dietary and economical changes that took place during Early Neolithic in Iberia. MATERIAL AND METHODS: Here we apply carbon and nitrogen stable isotope analysis to bone collagen from 4 humans and 64 faunal samples from 14 different species. The large dataset belongs to the same unique chrono-cultural context secured by 20 radiocarbon dates. Three direct new radiocarbon dates were carried out on the human remains analyzed. RESULTS: Faunal isotope values show no significant differences between wild and domestic herbivores, although the latter have more homogeneous values. Domestic pigs, potentially considered omnivorous, also show signatures of a herbivore diet. Human isotopic results show a diet mainly based on terrestrial C3 resources and possibly high meat consumption. The only individual found buried with a special funerary treatment presents a slightly different protein intake, when taking into account the long contemporaneous baseline analyzed. DISCUSSION: Similar values between wild and domestic species could be the result of common feeding resources and/or grazing on the same parts of the landscape. The herbivore diet seen amongst domestic pigs rules out feeding on household leftovers. High meat consumption by humans would support the hypothesis of the existence of a specialized animal husbandry management community in which agriculture was not intensively developed. Our results suggest that the development of agricultural practices and animal husbandry were not necessarily associated together in the early stages of the Western Mediterranean Neolithic.

Elemental turnover rates and trophic discrimination in juvenile Lebranche mullet Mugil liza under experimental conditions.

The aim of this study was to determine the isotopic-turnover rate (RIT ) and trophic-discrimination factor (FTD ) in muscle tissues of Lebranche mullet Mugil liza fed an experimental diet (δ13 C = -27·1‰; δ15 N = 1·0‰). Juvenile M. liza exhibited a relatively fast RIT , with a half-life (t50 ) of only 16 and 14 days for δ13 C and δ15 N respectively and a nearly complete isotopic turnover (t95 ) of 68 and 60 days for δ13 C and δ15 N.

Do marine protected areas influence mercury exposure? Insights from a shark community in the tropical Northeast Pacific.

Biomass depletion caused by overfishing is likely to alter the structure of food webs and impact mercury transfer to marine predators. Although marine protected areas (MPAs) are spared from fishing pressure, their influence on biota mercury levels is poorly understood. Here, we used carbon and nitrogen stable isotope compositions as well as mercury concentrations in fin clips to characterize foraging habitat and mercury exposure of a shark community composed of migratory and resident species of the Revillagigedo archipelago, an offshore MPA in the Northeast Pacific off Mexico. We found that the probability of finding migratory sharks in the isotopic niche of Revillagigedo-resident sharks was low, likely reflecting the use of habitats outside the archipelago by highly mobile species. Community-wide variations in mercury were primarily explained by shark length, revealing that bioaccumulation was the main driver of Hg concentrations. We failed to detect a clear effect of foraging habitat on shark mercury exposure, which may be related to migratory species using both exploited and protected areas when moving outside the Revillagigedo MPA. More similar studies on the potential mitigation of Hg contamination by MPAs are needed in the future if fishing pressure increases to satisfy the growing global human population.

140 years-long sedimentary records of PAHs and CN stable isotopes from Ninomiya River, Japan.

Anthropogenic activities' impacts over 140 years were studied at West Nanao Bay using a variety of geochemical techniques on sedimentary records. The bay is influenced by the Ninomiya River which is fed by a small watershed at which Tatzuruhama Town is located. Sedimentation rate was calculated using 210Pb-excess and 137Cs activities. C/N decreased after 1975, indicating a decrease in lignin-rich organic matter. From δ13C, δ15N and biogenic silica it was indicated that the population increased sewage-discharges until the construction of waste-water treatment plant in 1986. Several recorded changes in the landuse matched with the variation of the particle size. Total PAHs concentration was 1.17-62.78 µg g-1, being highest during Japan's fastest economic growth period (1946-1975). Using diagnostic ratios and PCA analysis, PAHs' sources were identified as pyrogenic for all depths, varying from coal combustion (90.7 %) before 1946 to a mixture of biomass and vehicle combustion after 1961.

Mercury concentrations, biomagnification and isotopic discrimination factors in two seabird species from the Humboldt Current ecosystem.

Assessing mercury (Hg) biomagnification requires the description of prey-predator relationships, for each species and ecosystem, usually based on carbon and nitrogen isotope analyses. Here, we analyzed two seabirds from the Humboldt Current ecosystem, the Guanay cormorant (Phalacrocorax bougainvillii) and the Peruvian booby (Sula variegata), as well as their main prey, the Peruvian anchovy (Engraulis ringens). We reported Hg concentrations, Hg biomagnification (BMF) and isotopic discrimination factors (Δ13C and Δ15N) in seabird whole blood. BMFs and Δ13C in our study (on wild birds where diet was not controlled) were similar to other piscivorous seabirds previously studied in captive settings, but Δ15N were lower than most captive experiments. We observed lower Hg concentrations in Humboldt seabirds compared to other oligotrophic ecosystems, possibly due to Hg biodilution in the high biomass of the first trophic levels. This work calls for a better characterization of Hg trophic dynamics in productive upwelling ecosystems.

TrophicCS: Spatialized trophic data of the Celtic Sea continental shelf food web.

Understanding the dynamics of species interactions for food (prey-predator, competition for resources) and the functioning of trophic networks (dependence on trophic pathways, food chain flows, etc.) has become a thriving ecological research field in recent decades. This empirical knowledge is then used to develop population and ecosystem modeling approaches to support ecosystem-based management. The TrophicCS data set offers spatialized trophic information on a large spatial scale (the entire Celtic Sea continental shelf and upper slope) for a wide range of species. It combines ingested prey (gut content analysis) and a more integrated indicator of food sources (stable isotope analysis). A total of 1337 samples of large epifaunal invertebrates (bivalve mollusks and decapod crustaceans), zooplankton, fish, and cephalopods, corresponding to 111 taxa (94% determined at the species level), were collected and analyzed for stable isotope analysis of their carbon and nitrogen content. Samples were collected between 2014 and 2016, mostly during the month of November and between 57 and 516 m depth. Sample size varied between taxa (from 1 to 52), with 98 taxa having at least three samples. The gut contents of 1027 fish belonging to 10 commercially important species: black anglerfish (Lophius budegassa), white anglerfish (Lophius piscatorius), blue whiting (Micromesistius poutassou), cod (Gadus morhua), haddock (Melanogrammus aeglefinus), hake (Merluccius merluccius), megrim (Lepidorhombus whiffiagonis), plaice (Pleuronectes platessa), sole (Solea solea), and whiting (Merlangius merlangus) were analyzed. Sampling occurred in November 2014 and 2015. The gut content data set contains the occurrence of prey in gut, identified to the lowest taxonomic level possible. No prey were assigned for 274 empty gut contents. To consider potential ontogenetic diet changes, a large size range was sampled for each species. The TrophicCS data set was used to improve understanding of trophic relationships and ecosystem functioning in the Celtic Sea. Data are released under a CC-BY-NC-SA license, and please cite this paper when reusing the data.

Carbon and nitrogen stable isotopic offsets between diet and hair/feces in captive orangutans.

Estimating stable isotopic offset values is crucial for dietary reconstructions. Although research into stable isotope ecology of wild nonhuman primates is increasing overall, only a minority of studies involve laboratory experiments. This study is the first to report the carbon and nitrogen stable isotopic offset values in hair and feces of orangutans. During an experiment lasting 1 week, the weight of each consumed food item was recorded for each of six captive Bornean orangutan (Pongo pygmaeus) individuals. The food, hair, and fecal samples were collected for a few days, and their stable carbon and nitrogen isotope ratios were measured using an elemental analyzer/isotope ratio mass spectrometer. Subsamples of feces were treated with ethanol during the preservation process. Monte Carlo analyses showed that the 95% confidence intervals (CIs) of the carbon and nitrogen offset values between hair and diet were +0.9‰ to +3.9‰ and +2.3‰ to +4.5‰, respectively. The 95% CIs of the carbon and nitrogen offset values between feces and diet were -3.7‰ to -0.9‰ and +0.3‰ to +2.7‰, respectively. The effect of ethanol treatment on the stable isotope ratios of feces was unclear and inconclusive. The computed offset values of hair in captive orangutans are similar to those reported in other nonhuman primates, although those of feces showed greater interspecies variations. The offset values estimated in this study contribute to isotopic studies into the feeding ecology of free-ranging orangutans who are critically endangered in most wild settings.

Spatio-temporal stable isotope variation of a benthic primary consumer in a simple food web in a strongly acidic lake.

Analysis of aquatic food webs is typically undertaken using carbon and nitrogen stable isotope composition of consumer and producer species. However, the trophic consequences of spatio-temporal variation in the isotope composition of consumers have not been well evaluated. Lake Katanuma, Japan, is highly acidic and has only one dominant species of benthic alga and one planktonic microalga, making it a prime system for studying trophic relationships between primary consumers and producers. In this simple lake food web, we conducted a field survey to evaluate spatial and temporal variation in the carbon and nitrogen stable isotope composition of a chironomid larvae in association with a single benthic and planktonic alga. We found a significant correlation between carbon stable isotope ratios of the chironomid larvae and the benthic diatom species in the lake. Thus, chironomid larvae may represent a reliable isotopic baseline for estimating isotope values in benthic diatoms. However, although the correlation held in shallow water, at four m depths, there was no significant relationship between the isotope ratios of chironomids and benthic diatoms, probably because deep-water larvae spend part of their life cycle migrating from the lake shore to deeper water. The differing isotope ratios of deeper chironomid tissues likely reflect the feeding history of individuals during this migration.

[Trophic niche of medium-form and dwarf-form of purple flying squid Sthenoeuthis oualaniensis in the central and western South China Sea]. / å—æµ·ä¸­è¥¿éƒ¨æµ·åŸŸé¸¢ä¹Œè´¼ä¸­åž‹ç¾¤å’Œå¾®åž‹ç¾¤çš„è¥å »ç”Ÿæ€ä½.

To explore the characteristics of carbon and nitrogen stable isotope and trophic niche between two forms (medium-form and dwarf-form) of the purple flying squid Sthenoteuthis ouala-niensis, we collected samples from the central and western South China Sea in August 2017 to analyze the values of carbon and nitrogen stable isotope and the changes of trophic level for different mantle lengths. We further compared the trophic niche differences of the two forms populations. The results showed that for the medium-form, the δ13C value ranged from -19.54‰ to -18.10‰ and the δ15N value ranged from 7.79‰ to 9.45‰. The average trophic level of medium-form was 2.90 and ranged from 2.72 to 3.21. For the dwarf-form, the δ13C value ranged from -19.69‰ to -18.43‰, and the δ15N value ranged from 8.02‰ to 8.99‰. The average trophic level of the dwarf-form was 2.91 and ranged from 2.79 to 3.08. There were significant differences of δ15N but no differences of δ13C values between the medium-form and dwarf-form of purple flying squid. The mantle length had a significant impact on δ13C and δ15N, with the value of δ15N increasing with the mantle length. The trophic niche breadth and the trophic level of the medium-form purple flying squid were more diverse than those of dwarf-form.

Assessing the influence of migration barriers and feeding ecology on total mercury concentrations in Dolly Varden (Salvelinus malma) from a glaciated and non-glaciated stream.

Assimilation of mercury (Hg) into food webs is directly influenced by ecological factors such as local habitat characteristics, species feeding behavior, and movement patterns. Total Hg concentrations ([THg]) in biota from Subarctic latitudes are driven both by broad spatial processes such as long-range atmospheric transport and more local influences such as biovectors and geology. Thus, even relatively pristine protected lands such as national parks are experiencing Hg accumulation. We analyzed [THg] and stable isotopes of carbon (δ13C) and nitrogen (δ15N) in 104 Dolly Varden (Salvelinus malma) collected from two rivers in southeastern Alaska, upstream and downstream of apparent anadromous migration barriers in watersheds with and without glacial coverage. To assess the potential magnitude of marine-derived THg returning to freshwater, we analyzed [THg] in ten adult pink salmon from each study system. There were no differences in Dolly Varden mean [THg] between sites after the data were standardized for fork length, but unadjusted [THg] varied relative to fish size and δ15N values. While previous studies generally show that [THg] increases with higher δ15N values, we found that Dolly Varden below migration barriers and foraging on salmon eggs had the highest δ15N values among all sampled individuals, but the lowest [THg]. Dolly Varden residing below anadromous barriers had δ13C values consistent with marine influence. Since salmon eggs typically have low [Hg], our results suggest that abundant salmon populations and the dietary subsidy they provide may reduce the annual exposure to [Hg] in egg-eating stream fishes such as Dolly Varden. In addition to identifying a suitable species for freshwater Hg monitoring in southeastern Alaska, our study more broadly implies that river characteristics, location within a river, fish size, and feeding ecology are important factors influencing Hg accumulation.

Impacts of a high-discharge submarine sewage outfall on water quality in the coastal zone of Salvador (Bahia, Brazil).

Carbon and nitrogen stable isotopic signatures of suspended particulate organic matter and seawater biological oxygen demand (BOD) were measured along a coastal transect during summer 2015 to investigate pollution impacts of a high-discharge submarine sewage outfall close to Salvador, Brazil. Impacts of untreated sewage discharge were evident at the outfall site by depleted δ(13)Corg and δ(15)N signatures and 4-fold increased BOD rates. Pollution effects of a sewage plume were detectable for more than 6km downstream from the outfall site, as seasonal wind- and tide-driven shelf hydrodynamics facilitated its advective transport into near-shore waters. There, sewage pollution was detectable at recreational beaches by depleted stable isotope signatures and elevated BOD rates at high tides, suggesting high bacterial activity and increased infection risk by human pathogens. These findings indicate the urgent necessity for appropriate wastewater treatment in Salvador to achieve acceptable standards for released effluents and coastal zone water quality.

n-Alkanes and stable C, N isotopic compositions as identifiers of organic matter sources in Posidonia oceanica meadows of Alexandroupolis Gulf, NE Greece.

We analyzed n-alkane contents and their stable carbon isotope composition, as well as the carbon and nitrogen isotope composition (δ(13)C, δ(15)N) of sediment organic matter and different tissues of Posidonia oceanica seagrass sampled in Alexandroupolis Gulf (A.G.), north-eastern Greece, during 2007-2011. n-Alkane contents in P. oceanica and in sediments showed similar temporal trends, but relative to bulk organic carbon content, n-alkanes were much more enriched in sediments compared to seagrass tissue. Individual n-alkanes in sediments had similar values than seagrass roots and rhizomes and were more depleted in (13)C compared to seagrass leaves and sheaths, with δ(13)C values ranging from -35‰ to -28‰ and from -25‰ to -20‰, respectively. n-Alkane indexes such as the Carbon Preference Index, carbon number maximum, and n-alkane proxy 1 (C23+C25/C23+C25+C29+C31) indicate strong inputs of terrestrial organic matter, while the presence of unresolved complex mixtures suggests potential oil pollution in some sampled areas.

Carbon and nitrogen isotope ratios of mistletoes growing on nitrogen and non-nitrogen fixing hosts and on CAM plants in the Namib desert confirm partial heterotrophy.

Xylem-tapping mistletoe species growing on Mimosaccae, non-Mimosaceae and hosts performing Crassulacean acid metabolism (CAM) were studied along an aridity gradient in the Namib desert. °13C-values of mistletoes became more negative with decreasing nitrogen (N)-concentration in their leaves, while the host plants showed no such relationship. This might suggest that mistletoes regulate their water use efficiency according to the nitrogen supply from the host. However, further inspection of the data indicates that the relations of δ13C-values with leaf nitrogen in mistletoes may result from carbon input from the host. This is especially true for mistletoes growing on CAM plants which exhibit a very high δ13C-value, but show no evidence of CAM. It is calculated that about 60% of the carbon in mistletoes growing on C3 and on CAM hosts originated from the host. The hypothesis of Marshall and Ehleringer (1990) that xylem tapping mistletoes are also carbon parasites could explain the change in δ13C-values with N-supply and the difference in δ13C-values between mistletoes growing on C3 and CAM hosts.