bluuebunny/crossref_metadata_2025 huggingface dataset:
Quantitative Evaluation of Elastic Properties of Nano-Crystalline Nickel Using Atomic Force Acoustic Microscopy
Authors: Kopycinska-Müller M. , Caron A. , Hirsekorn S. , Rabe U. , Natter Harald , Hempelmann Rolf , Birringer Rainer , Arnold Walter
Published: February 2008

Atomic force acoustic microscopy (AFAM) is a near-field technique, where the vibration behavior of a micro-fabricated elastic cantilever beam in contact with a sample surface is sensitive to its local elastic properties. The resolution of this technique is given by the contact radius a
c of the atomic force microscope sensor-tip on the sample surface. Taking into account only the Hertzian forces, a
c depends on the static load applied by the cantilever, on the elastic constants of the tip and the sample and on the geometry of the contacting bodies. The shape of the sensor tip used in atomic force acoustic microscopy is between a sphere and a flat punch. Hence a
c extends from just below 10nm to a few tens of nanometers. In this review, we give an overview of the AFAM technique, present data on the indentation moduli of nanocrystalline nickel, and discuss some of the error sources in quantitative AFAM. The AFAM indentation moduli measured are comparable to the values obtained by nanoindentation and lower than the indentation moduli calculated from ultrasonic velocity measurements. There seems to be a decrease of the indentation modulus with decreasing grain size for grain sizes below 30nm. The data are discussed taking into account X-ray diffraction and electron back-scattering data revealing some texture and macro-strain due to internal stresses in the samples investigated.
Profiling Participative Residents in Western Communities*
Authors: Matarrita‐Cascante David , Luloff A.E.
Published: February 2008

AbstractDifferences between old‐timers and newcomers and their effects on community social dimensions have been the object of much research. These studies have shown how extensive in‐migration of people with different socioeconomic backgrounds, values, and perspectives contribute to heightened social conflict in some communities. Popular media accounts and some social science research referred to the conflict emerging from these differences as a culture clash. This study examines the effects that different backgrounds, attitudes, and behaviors have on community participation. Here, earlier work on differences in participation levels between seasonal and permanent residents is extended in an attempt to identify structural and interactional characteristics associated with participative citizens regardless of their residential status. A profile of participative residents was found. Knowing these characteristics helps identify people who could bring important and useful insights to local decision‐making. These residents make a deliberate choice to purposively engage in community efforts. Such voluntary interaction creates a pro‐community environment where needs and solutions are tackled by residents. Additionally, this interactive environment serves as a ground for the reduction of differences among community members. Through this process, community development is achieved, enhancing community well‐being.
Cry Wolf!: Narratives of Wolf Recovery in France and Norway*
Authors: Skogen Ketil , Mauz Isabelle , Krange Olve
Published: February 2008

Abstract Due to strict protection through the last decades, wolves have returned to many areas from which they have been absent for a long time. This is a conservation success story, but the wolves also cause conflicts wherever they arrive. We have studied the situation in southeastern Norway and in the French Alps, where the conflict patterns are similar. Diverging interpretations of the situation are supported by narratives, and two varieties have become increasingly significant in both countries. Rumors about the secret reintroduction of wolves are common among wolf adversaries. Another narrative, important to the pro‐wolf camp, is based on the notion that particular sheep husbandry practices (unattended rough grazing) are unique to either Norway or France—whereas there are in fact more similarities than differences. Yet, while the reintroduction‐conspiracy rumors are ridiculed, the notion of unique national conflict patterns has achieved a status almost of official truth. Furthermore, the story about natural wolf recovery is itself a value‐laden narrative, and not only “scientific fact.” The different status of these narratives tell us something about power relations: Given their different social basis, it seems relevant to consider the national uniqueness image and the natural recovery theory as tightly interwoven with symbolic power and the reintroduction conspiracy rumors as similarly interwoven with patterns of cultural resistance.
Landscape Effects on Growth of Age‐0 Arctic Grayling in Tundra Streams
Authors: Luecke Chris , MacKinnon Peter
Published: February 2008

The growth of age‐0 Arctic grayling Thymallus arcticus in two adjacent watersheds with differing numbers of lakes was compared. Age‐0 Arctic grayling grew faster in the watershed with numerous lakes (eight) than in the watershed with only one lake. The presence of lakes along the stream courses in both watersheds decreased stream temperatures in the spring but increased temperatures in summer. The size of substrates was greater in streams below lakes than in inlet stream reaches. Growth rates of discrete populations of age‐0 Arctic grayling were positively related to stream temperature. No relationship between fish growth rate and the biomass of invertebrate drift was apparent. We conclude that the summer increase in stream temperatures attributable to the presence of lakes resulted in increased growth of Arctic grayling in the watershed with numerous lakes. A simulation model of the temperature‐dependent growth of age‐0 Arctic grayling indicated that the abundance of lakes in one of the watersheds enhanced the potential production of Arctic grayling almost sixfold.
Climate Regime Effects on Pacific Herring Growth Using Coupled Nutrient‐Phytoplankton‐Zooplankton and Bioenergetics Models
Authors: Rose Kenneth A. , Megrey Bernard A. , Hay Douglas , Werner Francisco , Schweigert Jake
Published: February 2008

We used a nutrient‐phytoplankton‐zooplankton (NPZ) model coupled to a fish bioenergetics model to simulate the weight‐at‐age responses of Pacific herring Clupea pallasii to climate regimes. The NPZ model represents the daily dynamics of the lower trophic levels by simulating the uptake and recycling dynamics of nitrogen and silicon and the photosynthesis and grazing interactions of multiple functional groups of phytoplankton and zooplankton. The bioenergetics model simulates the number and mean weight of Pacific herring for each of 10 age‐classes. Three zooplankton groups simulated in the NPZ model provide estimates of the prey used to determine the consumption component of the herring bioenergetics model. We used a spawner‐recruit relationship to estimate the number of new age‐1 individuals joining the herring population every year. The coupled models were applied to the coastal upwelling area off the west coast of Vancouver Island. Model simulations were performed to isolate the effects of each of four documented climate regimes on Pacific herring weights at age. The climate regimes differed in the environmental variables used in the spawner‐recruit relationship as well as in the water temperature, mixed‐layer depth, and nutrient influxing rate used by the NPZ model. In agreement with general opinion and with the Pacific herring data from the west coast of Vancouver Island, the model‐predicted estimates of weight at age, recruitment, and spawning stock biomass were highest in regime 1 (1962‐1976), intermediate in regime 2 (1977‐1988), and lowest in regime 3 (1989‐1999). Insufficient time has passed to adequately document the conditions and herring responses in regime 4 (1998‐2002). The overall regime effect on weights at age was a mix of recruitment effects and lower trophic level effects that varied in direction and magnitude among the four regimes. Coupling bioenergetics models to physics and food web models is the next challenge in understanding and forecasting how climate change will affect fish growth and population dynamics.
Bioenergetics Modeling in the 21st Century: Reviewing New Insights and Revisiting Old Constraints
Authors: Chipps Steven R. , Wahl David H.
Published: February 2008

The development and application of fish bioenergetics models have flourished in recent years, due in part to the complexity of the issues being faced by fisheries biologists. As with any model, the accuracy of bioenergetics models can be hampered by uncertainty in model parameters. A review of the literature showed that field and laboratory tests of bioenergetics models often result in poor agreement between model predictions and independent data. Nonetheless, bioenergetics modeling continues to be used to make important management decisions. Recent tests of model predictions have shown that parameter uncertainty is influenced by factors such as feeding rate, physiological adaptations, and prey composition and abundance. In an attempt to reduce the uncertainty in modeling applications, we propose a framework that highlights the importance of (1) model evaluation, (2) hypothesis‐based parameter testing, and (3) improved communication between model developers and model users. Adherence to this framework will help reduce uncertainty in modeling applications and simultaneously contribute to a broader knowledge of fish physiology and feeding ecology.
Enhancing Bioenergetics Models to Account for Dynamic Changes in Fish Body Composition and Energy Density
Authors: Breck James E.
Published: February 2008

Fish proximate composition and energy density can influence growth, survival, and reproduction, so it is important to develop models to understand the patterns and predict dynamic changes. This paper presents three such models. Model 1 describes the general pattern of changes in lipid, protein, ash, and energy density that occur with changes in water content. The key assumption this model is that there is a fixed amount of water associated with each gram of protein and a much smaller fixed amount of water associated with each gram of lipid. In combination with a mass balance constraint, this explains the commonly observed linear relationship between the fraction lipid and the fraction water. Because energy density varies in direct proportion to the fractions lipid and protein, the linear relationship between body composition and fraction water makes energy density also a linear function of the fraction water. The model is fitted to data for lake trout Salvelinus namaycush and coho salmon Oncorhynchus kisutch for a limited range in wet weight. Model 2 describes the pattern of proximate composition and energy density that occurs with variation in body size. A strong pattern was found between the mass of water and the mass of protein, suggesting strict control of body water. The model is fitted to data for common carp Cyprinus carpio and bluegill Lepomis macrochirus. This analysis shows that the relationship between body composition, energy density, and fraction water is expected to vary with body size because both the water: Protein ratio and the fraction ash change with body size. Model 3 demonstrates how this approach can be used to predict changes in fish body composition and energy density during starvation, as might be done with a bioenergetics model. This model is fitted to data from a starvation experiment involving largemouth bass Micropterus salmoides.
Refinement and Testing of a Brook Trout Bioenergetics Model
Authors: Hartman Kyle J. , Cox M. Keith
Published: February 2008

The brook trout Salvelinus fontinalis is an important species across North America, being the focus of restoration and conservation efforts in the eastern United States and considered a threat to native salmonids in the western part of the country. Bioenergetics models have emerged as useful tools for studying the ecology and management of fish species, but these models should be critically evaluated prior to widespread application. We conducted laboratory experiments to refine model parameters (metabolism and the activity multiplier) and to test a model for brook trout. Brook trout metabolic rates increased with temperature up to 20°C, then declined sharply. Specific metabolism declined with increasing fish size. Validation experiments conducted for 7, 21, and 31 d at 12‐16°C showed that the model predicted consumption within 1.6 ± 3.6%, growth within 2.3 ± 12.5%, and final weight within 1.7 ± 5.1% of measured values. The results of this study will allow biologists to better use bioenergetics models to study the trophic dynamics of brook trout throughout their range.
Bioenergetics Modeling: Progress since the 1992 Symposium
Authors: Hartman Kyle J. , Kitchell James F.
Published: February 2008

A symposium held at the annual meeting of the American Fisheries Society in Rapid City, South Dakota, in 1992 provided an overview of bioenergetics modeling and led to the publication of a series of papers in the Transactions of the American Fisheries Society the next year. Since then, Wisconsin Sea Grant has published a new version of its bioenergetics software (Fish Bioenergetics 3.0) and a manual to facilitate use of that model. Review of the more recent literature reveals continuing development and application of this modeling approach. A symposium held at the annual meeting in Madison, Wisconsin, in 2004 provided an opportunity for reporting progress and concerns about the “Wisconsin model.” This special section stems from the papers presented at that meeting.
Measurement of early-age temperature rises in concrete made with blended cements
Authors: Dhir R. K. , Zheng L. , Paine K. A.
Published: February 2008

The advisability of controlling the temperature rise and fall in concrete at early age is well recognised as one of the factors preserving long-term performance and durability of structures. Of particular importance in design of water-retaining and massive concrete structures is T1, the difference between peak temperature of the section and mean ambient temperature. In previous studies, a cement hydration model was developed in order to predict T1 for concrete made with low heat (LH) and very low heat (VLH) special cements. To test this model, a study was carried out to measure the early-age temperature rises for concrete elements containing blended cements, meeting the requirements for the LH and VLH classes. The effects of cement heat class, cement content, formwork type and section thickness on the temperature rise were evaluated for both cement types. Verification of the established models was evaluated by comparing measured temperature rises with those predicted. It was found that the model proposed in previous studies gave satisfactory prediction of T1 values.
Shortcomings of geometrical approach in multi-species modelling of chloride migration in cement-based materials
Authors: Friedmann H. , Amiri O. , Aït-Mokhtar A.
Published: February 2008

Chloride migration tests and chronoamperometries were carried out on three cement mortars with different water/cement (w/c) ratios. The electrical current of the chloride migration is simulated with a multi-species model, which takes into account the geometrical properties of the pore structure throughout the diffusibility ratio. The comparison between the measured and the simulated currents shows a significant difference: systematically, simulated currents evolve faster than those measured. From these results, it appears that the purely geometrical approach alone is insufficient correctly to describe the transport of ionic species in cement-based materials. Finally, it is shown that the introduction of a ‘viscoelectric effect’, which conveys the electrical double-layer effect (EDL), improves the results of the model. As a first approach the EDL is taken into account empirically by considering a reducing factor 1/rD applied to the effective diffusion coefficients of the cations. This factor is deduced from Truc's work.
Polypropylene fibres in heated concrete. Part 1: Molecular structure and materials behaviour
Authors: Khoury G. A. , Willoughby B.
Published: February 2008

Polypropylene fibres are employed in concrete to combat explosive spalling in fire, but the molecular structure and the materials properties are not well understood. The current paper presents the physical, chemical, thermal and mechanical characteristics of polypropylene fibres as functions of temperature in the solid, melt and vapour states in relation to the structure and properties of heated concrete. This forms the foundation for the better understanding of the processes underlying the behaviour of the polypropylene–concrete composite that beneficially influence the risk of spalling and also provides data necessary for thermo-hydro-mechanical numerical modelling.
Strength and deformation characteristics of bottle-shaped struts
Authors: Sahoo D. K. , Gautam R. K. , Singh B. , Bhargava P.
Published: February 2008

Isolated strut tests were performed under monotonically increasing displacement controlled in-plane loading on thin plain, steel fibrous and reinforced concrete panels to determine the strength and deformation characteristics of bottle-shaped struts for use in strut-and-tie modelling. A total of 12 concrete panels were tested to failure. The results were used to evaluate the performance of reinforced struts and explore the possibility of using steel fibrous concrete in bottle-shaped struts. ACI 318–05 recommends a strut efficiency factor of 0·75 for an effective transverse reinforcement content greater than or equal to 0·3%. However, a recent study has indicated that the strut efficiency factor is insensitive to reinforcement in the strut. The results of this investigation reveal that reinforcement indeed has a significant influence on strut efficiency and the use of steel fibrous concrete in reinforced struts improves their toughness and post-peak response compared to that of non-fibrous-reinforced concrete struts.
Variable toxicity of ionic liquid–forming chemicals to Lemna mino and the influence of dissolved organic matter
Authors: Larson James H , Frost Paul C , Lamberti Gary A
Published: February 2008

Ionic liquids (ILs) are nonvolatile organic salts that remain liquid over a wide range of temperatures. Ionic liquids are promoted as environmentally friendly alternatives to the volatile organic solvents that are currently in widespread industrial usage. Although ILs are unlikely to contribute to air pollution, their potential effects on aquatic ecosystems are largely unknown. Furthermore, information is lacking on how ILs will interact with common features of aquatic environments, such as dissolved organic matter (DOM). We assessed the effect of five IL-forming chemicals on the growth of duckweed, Lemna minor, a common aquatic vascular plant. In general, 1-alkyl-3-methylimidazolium chemicals with longer alkyl chains were more toxic to L. minor than those with short alkyl chain lengths. The concentration that produced a 50% reduction (the EC50) in root growth was 8.56 ppm when a butyl chain was present but was 0.25 ppm (i.e., much more toxic) when an octyl chain was substituted. Butyl-substituted 3-methylpyridinium (root growth EC50 of 7.49 ppm) and 3-methylimidazolium cations had similar toxicity, whereas a tetrabutyl ammonium cation was considerably less toxic (root growth EC50 of 32.71 ppm). When we tested whether DOM reduced the toxicity of these cations, we saw no effect of a low-molecular-weight organic acid or commercial humic matter. In contrast, natural DOM reduced the toxicity of imidazolium, but only at low concentrations. Design and use of ILs and other new chemicals should incorporate not only standard toxicity tests but also information on how such chemicals will interact with other components of aquatic ecosystems.
Effects of arsenic speciation and low dissolved oxygen condition on the toxicity of arsenic to a lotic mayfly
Authors: Irving Elaine C , Lowell Richard B , Culp Joseph M , Liber Karsten , Xie Qianli , Kerrich Robert
Published: February 2008

The influence of site-specific conditions on contaminant bioavailability and toxicity to benthic invertebrates is a key consideration in the environmental risk assessment process. This is particularly relevant for contaminants with complex speciation chemistries, such as arsenic. The present study addressed uncertainties regarding arsenic toxicity to a mayfly (Baetis tricaudatus) under low dissolved oxygen (DO) conditions characteristic of many contaminated sites. Arsenic toxicity (arsenite, As(III); arsenate, As(V)) to mayfly nymphs was assessed under two DO scenarios (68 and 84% saturation). Arsenic speciation ratios were determined during testing to confirm the nature of arsenic exposure. The present study found that As(III) was more lethal and bioaccumulated to a greater degree in B. tricaudatus compared to As(V), but the sublethal toxicities of the two arsenic species were similar. Nymph growth and development were significantly inhibited after 12 d of exposure to both 1 mg/L of As(III) and As(V). Exposure to arsenic under low DO conditions (6.5 mg/L, 68% saturation) did not significantly affect As(III) or As(V) toxicity and bioaccumulation over 12 d. The DO level of 6.5 mg/L, however, appeared to be marginally lethal to B. tricaudatus. Results indicate that the Canadian arsenic criterion for the protection of aquatic life (5 μg/L) is protective of B. tricaudatus and is low enough to accommodate differences in arsenic toxicity because of the interconversions between As(III) and As(V). These findings provide insight regarding the toxicity and speciation of arsenic under DO conditions considered to be low for this lotic mayfly species and representative of existing conditions at mine sites in northern Canada.
Cadmium, iron, and zinc uptake individually and as a mixture by Limnodrillus hoffmeisteri and impact on adenosine triphosphate content
Authors: Ortega Ma de los Angeles Grajeda y , López Eugenia López , Perotzi Liliana Favari , Garduño-Siciliano Leticia , Martínez Marcela Galar
Published: February 2008

Heavy metals, such as Fe, Zn, and Cd, are major pollutants in aquatic ecosystems. These toxicants usually are present in these ecosystems in the form of mixtures, and their effect on exposed organisms is the result of interactions occurring between the metals as well as with other pollutants and environmental factors. The present study evaluated the uptake of Cd, Fe, and Zn individually and as a mixture and their effect on adenosine triphosphate (ATP) content in Limnodrillus hoffmeisteri, an important aquatic organism given its resistance to large amounts of these xenobiotics. Test organisms were exposed for 96 h to sediment treated with each of these metals individually and as a mixture. The metal concentrations used were equivalent to the zero lethal concentration of these pollutants as determined in a previous study. At the end of the exposure period, metal concentration in medium and organism as well as ATP content in the latter were quantified. Metal uptake was measured by determining the bioconcentration factor at 96 h. All three metals elicited an important decrease in ATP content when acting singly and as part of a mixture. When present as a mixture, their uptake and effect on L. hoffmeisteri are modified. Therefore, a joint-action toxicity approach should be used for toxicity evaluations involving these pollutants.
Dose-dependent uptake, elimination, and toxicity of monosodium methanearsonate in adult zebra finches (Taeniopygia guttata)
Authors: Albert Courtney A , Williams Tony D , Morrissey Christy A , W.M.-Lai Vivian , Cullen William R , Elliott John E
Published: February 2008

Monosodium methanearsonate (MSMA), an arsenic-based pesticide, has been used for the past 10 years in attempts to suppress mountain pine beetle (Dendroctonus ponderosae) outbreaks in British Columbia, Canada. Previous studies have shown that cavity nesting forest birds such as woodpeckers forage and breed in MSMA treated pine stands. Here we examined the effects of MSMA in the laboratory using the zebra finch (Taeniopygia guttata), with the objective to examine tissue distribution and sublethal toxic effects in a model avian species. Zebra finches were exposed to this pesticide at doses similar to those found in bark beetle samples from MSMA stands of trees treated in the southern interior of British Columbia (8, 24, and 72 μg/g/d and a control group). Results showed high excretion (>90%) of arsenic in all dose groups, as well as dose-dependent trends in accumulation of arsenic in the blood (p < 0.001) and specific tissues. Monomethylarsonic acid, MMA (V), was the predominant form of arsenic in the blood plasma. Dimethylarsinic acid was the major form of arsenic found in the liver (83%) and kidney (61%) tissues. The brain tissue contained primarily the MMA (V) form (57%). Significant weight loss occurred in the two highest dose groups (p < 0.05). Birds in the highest dose group lost up to 15% of initial body mass.
Alteration of leaf decomposition in copper-contaminated freshwater mesocosms
Authors: Roussel Helene , Chauvet Eric , Bonzom Jean-Marc
Published: February 2008

The influence of copper on leaf litter decomposition was examined in experimental streams. Controls and three levels of contamination (5, 25, and 75 μg/L) were tested in triplicate in 20-m-long mesocosms. Equal quantities of alder, maple, and oak leaves were enclosed in mesh bags and placed in the upper and lower mesocosm sections that exhibited different habitat characteristics (shallow with pebble substrate or deep with fine substrate and macrophytes, respectively). Decomposition rate in the upper section of the 75 μg/L mesocosms was significantly reduced to 28% of control values. No significant reductions in the decomposition rate were seen in the lower section. No differences in the leaf-associated mycelial biomass and sporulation rates were observed between treatments, but they were consistently higher in the upper sections. The aquatic hyphomycete community was not affected by the contamination. The abundances of total leaf-associated macroinvertebrates and the dominant shredder (Gammarus pulex) were considerably reduced in the upper sections at 75 μg/L. Therefore, the reduced leaf decomposition probably resulted from a reduction in the abundance of macroinvertebrate detritivores. In addition, local variations in physical and biological characteristics of the habitat along the mesocosms significantly influenced the effects of copper on leaf-associated decomposers.
Behavior of Corophium volutator (Crustacea, Amphipoda) exposed to the water-accommodated fraction of oil in water and sediment
Authors: Kienle Cornelia , Gerhardt Almut
Published: February 2008

We investigated the short-term effects of the water accommodated fraction (WAF) of weathered Forties crude oil on the behavior of Corophium volutator in the Multispecies Freshwater Biomonitor® (MFB). When exposing C. volutator to 25 and 50% WAF in aqueous exposures, hyperactivity with an additional increase in ventilation was detected, whereas exposure to 100% WAF led to hypoactivity (narcosis). In a sediment exposure with 100% WAF, there was an increased tendency toward hyperactivity. In a pulse experiment, hyperactivity appeared at and after a 130-min exposure to 50% WAF in a majority of cases. Our experiments suggest that the behavior of C. volutator as measured in the MFB may be an appropriate parameter for coastal monitoring.
DNA microarray application in ecotoxicology: Experimental design, microarray scanning, and factors affecting transcriptional profiles in a small fish species
Authors: Wang Rong-Lin , Biales Adam , Bencic David , Lattier David , Kostich Mitch , Villeneuve Dan , Ankley Gerald T , Lazorchak Jim , Toth Greg
Published: February 2008

The research presented here is part of a larger study of the molecular mode of action of endocrine-disrupting chemicals targeting the hypothalamic–pituitary–gonadal axis in zebrafish (Danio rerio). It addresses several issues critical to microarray application in aquatic ecotoxicology: experimental design, microarray scanning, gene expression intensity distribution, and the effect of experimental parameters on the zebrafish transcriptome. Expression profiles from various tissues of individual zebrafish exposed to 17α-ethinylestradiol (30 ng/L), fadrozole (25 μg/L), or 17β-trenbolone (3.0 μg/L) for 48 or 96 h were examined with the Agilent Oligo Microarray (G2518A). As a flexible and efficient alternative to the designs commonly used in microarray studies, an unbalanced incomplete block design was found to be well suited for this work, as evidenced by high data reproducibility, low microarray-to-microarray variability, and little gene-specific dye bias. Random scanner noise had little effect on data reproducibility. A low-level, slightly variable Cyanine 3 (Cy3) contaminant was revealed by hyperspectral imaging, suggesting fluorescence contamination as a potential contributor to the large variance associated with weakly expressed genes. Expression intensities of zebrafish genes were skewed toward the lower end of their distribution range, and more weakly expressed genes tended to have larger variances. Tissue type, followed in descending order by gender, chemical treatment, and exposure duration, had the greatest effect on the overall gene expression profiles, a finding potentially critical to experimental design optimization. Overall, congruence was excellent between quantitative polymerase chain reaction results and microarray profiles of 13 genes examined across a subset of 20 pairs of ovarian samples. These findings will help to improve applications of microarrays in future ecotoxicological studies.
Trace element and metallothionein concentrations in seabirds from the Canadian Arctic
Authors: Braune Birgit M , Scheuhammer Anton M
Published: February 2008

Livers and kidneys were collected for five seabird species from the Canadian Arctic during the 1983 and 1991 to 1993 breeding seasons. Livers were analyzed for Cd, Hg, Pb, and Se, and kidneys were analyzed for Cd, Cu, Zn, and metallothionein (MT). Concentrations of the essential elements, Cu and Zn, were in agreement with those previously published in the literature. Thick-billed murres (Uria lomvia) from Ivujivik on the Hudson Strait/Hudson Bay coast in northwestern Quebec (Canada) had the highest mean renal concentrations of Cu, Zn, and Cd. Among the four species collected from Prince Leopold Island, northern fulmars (Fulmarus glacialis) had the highest hepatic concentrations of both Cd and Hg. The highest Se concentrations were found in northern fulmars and black-legged kittiwakes (Rissa tridactyla) from Prince Leopold Island. Hepatic Pb concentrations were low (<0.3 μg/g dry wt) in all species at all locations. Metallothionein concentrations were positively correlated with Cd and Zn for all species combined but were not correlated with Cu in any species. No significant relationships were found between MT and Cu or Zn in black guillemots (Cepphus grylle) or glaucous gulls (Larus hyperboreus). To our knowledge, this is the first report of MT concentrations and their relationships with trace metals in Arctic seabirds.
Chronic exposure to low concentrations of waterborne cadmium during embryonic and larval development results in the long-term hindrance of antipredator behavior in zebrafish
Authors: Kusch Robin C , Krone Patrick H , Chivers Douglas P
Published: February 2008

Cadmium has been recognized for some time as a potent environmental pollutant with the capability of disrupting olfactory-mediated behaviors. Failing to respond to chemical cues in the environment could adversely affect foraging, reproduction and predator avoidance. Recognizing this impaired perception as a serious ecological problem has been undermined by the fact that the damage is often reversible; short depuration periods of 5 d may allow for the re-establishment of responses to chemical cues. In this experiment, early life stage zebrafish were continuously exposed for 50 d at 0, 0.2, 2.0, and 20 μg Cd/L. The subjects were depurated for 14 d and then subjected to behavioral testing where antipredator responses to chemical alarm cues were observed. Our data show that continuous exposure during rearing to a concentration as low as 20 μg Cd/L is sufficient at eliminating antipredator behavior in zebrafish (Danio rerio) even after the source of the cadmium had been removed for 14 d. Furthermore, subjects raised under a 10-fold lower concentration also showed alteration in their behavioral responses, taking significantly longer to respond to the predation threat. Exposure to low levels of cadmium throughout development may alter neurogenesis, subsequently resulting in long-term impairment of chemical cue perception.
Metals affect soil bacterial and fungal functional diversity differently
Authors: Stefanowicz Anna M , Niklińska Maria , Laskowski Ryszard
Published: February 2008

Heavy metals can cause a decrease in the taxonomic diversity of soil communities. Because of functional redundancy, it remains unclear to what extent different functions performed by the soil microbial communities may be affected by pollution. We studied the impact of metal contamination on soil bacterial and fungal functional diversity, active microbial biomass, and soil respiration rate. Soil samples were collected from 39 sites along three forest and five meadow pollution transects near an abandoned Pb/Zn smelter in Avonmouth (UK) and Ni smelter in Clydach (UK), in a Cu mining and smelting region near Glogow (Poland), and in a Zn/Pb mining and smelting region near Olkusz (Poland). Biolog® GN2 and SFN2 plates were used to study the bacterial and fungal functional diversity, which subsequently was expressed as Shannon's diversity index (H′). The active microbial biomass was measured as substrate-induced respiration. We found that the bacterial functional diversity significantly decreased, whereas the fungal functional diversity slightly increased, with increasing metal concentration. We also observed a slight negative effect of metal pollution on the active microbial biomass. No relationship was found between metal contamination and total soil respiration rate. This suggests a higher sensitivity of bacterial functional diversity as an indicator for the effects of metal pollution compared with overall soil respiration. All microbial parameters were affected by nutrient concentrations and/or soil pH.
Mixture toxicity and gene inductions: Can we predict the outcome?
Authors: Dardenne Freddy , Nobels Ingrid , de Coen Wim , Blust Ronny
Published: February 2008

As a consequence of the nature of most real-life exposure scenarios, the last decade of ecotoxicological research has seen increasing interest in the assessment of mixture ecotoxicology. Often, mixtures are considered to follow one of two models, concentration addition (CA) or response addition (RA), both of which have been described in the literature. Nevertheless, mixtures that deviate from either or both models exist; they typically exhibit phenomena like synergism, ratio or concentration dependency, or inhibition. Moreover, both CA and RA have been challenged and evaluated mainly for acute responses at relatively high levels of biological organization (e.g., whole-organism mortality), and applicability to genetic responses has not received much attention. Genetic responses are considered to be the primary reaction in case of toxicant exposure and carry valuable mechanistic information. Effects at the gene-expression level are at the heart of the mode of action by toxicants and mixtures. The ability to predict mixture responses at this primary response level is an important asset in predicting and understanding mixture effects at different levels of biological organization. The present study evaluated the applicability of mixture models to stress gene inductions in Escherichia coli employing model toxicants with known modes of action in binary combinations. The results showed that even if the maximum of the dose–response curve is not known, making a classical ECx (concentration causing x% effect) approach impossible, mixture models can predict responses to the binary mixtures based on the single-toxicant response curves. In most cases, the mode of action of the toxicants does not determine the optimal choice of model (i.e., CA, RA, or a deviation thereof).
Effect of copper complexation on the estrogenic activities of endocrine-disrupting compounds using E-screen bioassay
Authors: Park Jong Yol , Lee Byoung Cheun , Ra Jin Sung , Lee Jiho , Kim Sang Don
Published: February 2008

The complexation reaction between Cu and four targeted endocrine-disrupting compounds (EDCs)—17β-estradiol (E2), 17α-ethynylestradiol (EE2), 4-octylphenol (OP), and bisphenol A (BPA)—was studied using the fluorescence quenching method, with the changed EDC forms evaluated for their estrogenic activities using an E-screen assay. The results of the E-screen showed no estrogenic activity of Cu, whereas results with the EDCs indicated high cell proliferation (decreasing order of induction: E2, EE2, OP, and BPA). The results of the fluorescence quenching response and FTIR (Fourier transformation infrared) strongly support the formation of Cu complexes on the –OH functional group of the targeted EDCs when Cu was spiked at concentrations between 10−7 and 10−4 M. The degree of complexation was in the following order: E2, EE2, OP, and BPA. The E-screen result for three of the EDCs, with the exception of BPA, was similar when estimating the effects of Cu on the estrogenic activities of the EDCs, which were significantly reduced at α = 0.05 with increasing Cu concentration. Consequently, the results of the complexation reaction and E-screen assay with the Cu-EDC mixtures indicated that Cu plays a significant role in the assessment of the estrogenic activities of EDCs in natural waters.
Temporal and spatial variation in solar radiation and photo-enhanced toxicity risks of spilled oil in Prince William Sound, Alaska, USA
Authors: Barron Mace G , Vivian Deborah , Yee Susan H , Diamond Steve A
Published: February 2008

Solar irradiance (W/m2) and downwelling diffuse attenuation coefficients (Kd; 1/m) were determined in several locations in Prince William Sound (AK, USA) between April 2003 and December 2005 to assess temporal and spatial variation in solar radiation and the risks of photo-enhanced toxicity from spilled oil. Weekly irradiance measurements of surface visible light, ultraviolet B (UVB), and ultraviolet A (UVA) radiation in Valdez (AK, USA) followed expected trends of maximum solar irradiance at each summer solstice and minimum values at each winter solstice. Variation from weekly maximum expected surface irradiances was attributed to large variations in environmental conditions over the 142-week monitoring period. Season and proximity to glacial meltwater were significant determinants of Kd, with 1% attenuation depths ranging from 0.4 to 15 m (UVB and UVA) and from 0.5 to 28 m (visible light). The probability of photo-enhanced toxicity risks estimated from UVA dosimetry decreased with increasing water depth, with higher risks during spring and summer and lower risks during fall and winter. These results demonstrate substantial temporal and spatial variation in solar radiation in Prince William Sound and the potential for significant season- and location-specific photo-enhanced toxicity risks from spilled oil.
Survival rates and blood metal concentrations in two species of free-ranging North American sea ducks
Authors: Wayland Mark , Drake Kiel L , Alisauskas Ray T , Kellett Dana K , Traylor Joshua , Swoboda Cindy , Mehl Katherine
Published: February 2008

Populations of several species of North American sea ducks have declined in the past few decades. Exposure to environmental contaminants, particularly metals, has been proposed as one of many possible factors contributing to these declines. Population dynamics are influenced by survival rates and breeding effort. In the present study, we examined the relationships between blood metal concentrations (Cd, Pb, Se, and Hg) and apparent annual survival and recapture probabilities (the latter as a surrogate for breeding effort) in adult females of two sea duck species, the king eider (Somateria spectabilis) and the white-winged scoter (Melanitta fusca), both of which have experienced declines in continental population during in recent years. No support was found for the hypothesis that exposure of white-winged scoters to these metals or of king eiders to Cd, Se, and Pb adversely affected probabilities of apparent annual survival. We detected a weak negative relationship ( = −0.833) between Hg and annual survival of king eiders, but the 90% confidence interval of the slope estimate overlapped zero (-2.439 to +0.672). Recapture probabilities were unrelated to concentrations of Cd, Se, and Pb in either species. Evidence indicated that Hg concentrations affected recapture probability in white-winged scoters ( = —194.77; 90% confidence interval, −203.770 to −185.778). Mercury levels were low in both species, and blood samples may not adequately represent long-term exposure to Hg. Therefore, conclusions regarding Hg effects on these birds should be considered with caution.
Ranking of agricultural pesticides in the rhine-meuse-scheldt basin based on toxic pressure in marine ecosystems
Authors: Jong Irmgard Henning-de , van Zelm Rosalie , Huijbregts Mark A.J , de Zwart Dick , van der Linden Ton M.A , Wintersen Arjen , Posthuma Leo , van de Meent Dik
Published: February 2008

Although risk assessments on a per-chemical basis are required during the registration procedure of pesticides, cumulative risks from the use of all pesticides on the variety of crops in a catchment area of a river are not assessed. The present study aimed to rank pesticides used in outdoor agricultural practice within the catchment of the rivers Rhine, Meuse, and Scheldt according to their potential toxic impact on the North Sea coastal ecosystem. Toxic pressure calculations (based on steady-state concentrations calculated with a multimedia fate model) and species-sensitivity distribution–based risk estimations were performed for pesticide emissions in the years 1998 (189 pesticides) and 2004 (133 pesticides). A ranking was established according to the relative contribution of single pesticides and crop types to the overall toxic pressure. Calculations were performed probabilistically to deal with parameter uncertainties. Only a few pesticides and crop types dominate overall toxic pressure because of emissions in both years, and the uncertainty appears to be caused largely by uncertainties in interspecies variances of aquatic toxicities. For 1998, these pesticides were fentin-acetate, with a median relative contribution (RCx) to the toxic pressure of multiple chemicals on an ecosystem of 0.43. For 2004, the pesticides that contributed most were pencycuron and paraquat-dichloride, with a median RCx of 4.4 × 10−2 and 3.9 × 10−2, respectively. Pesticides applied to potato cropland and fruit trees contributed most to the overall toxic pressure.
Using disposable polydimethylsiloxane fibers to assess the bioavailability of permethrin in sediment
Authors: Hunter Wesley , Xu Yiping , Spurlock Frank , Gan Jay
Published: February 2008

Pyrethroid insecticides are widely used in both agricultural and urban environments. Pyrethroids have been frequently detected in California, USA, stream bed sediments. Pyrethroids are strongly hydrophobic so their bioavailability is determined by their sorption to sediment. In the present study, we used disposable polydimethylsiloxane (PDMS) fibers to sample from the freely dissolved (effective) permethrin concentration that governs bioaccumulation and toxicity, and tested the correlation of those measurements with uptake by Chironomus tentans. In sediments that were incrementally diluted with silica sand, both PDMS fiber and organic carbon (OC) normalized sediment concentrations were highly correlated with C. tentans permethrin uptake. However, for multiple sediments with OC ranging from 1.4 to 27%, C. tentans permethrin uptake showed a better correlation with PDMS fiber concentrations than sediment OC-normalized concentrations. We conclude that the qualitative properties of sediment OC influence permethrin phase distribution and therefore the bioavailability of permethrin in sediment–water systems. Consequently selective methods such as PDMS fibers yield improved estimates of bioaccumulation and toxicity as such methods detect freely dissolved permethrin concentrations in the sediment.
Time and concentration dependency in the potentially affected fraction of species: The case of hydrogen peroxide treatment of ballast water
Authors: Smit Mathijs G.D , Ebbens Eltjo , Jak Robbert G , Huijbregts Mark A.J
Published: February 2008

Transport of large volumes of ballast water contributes greatly to invasions of species. Hydrogen peroxide (H2O2) can be used as a disinfectant to prevent the spread of exotic species via ballast water. Instead of using environmental risk assessment techniques for protecting a certain fraction of the species from being affected, the present study aimed to apply these techniques to define treatment regimes of H2O2 and effectively eliminate as many species as possible. Based on time-dependent dose–response curves for five marine species (Corophium volutator, Artemia salina, Brachionus plicatilis, Dunaliella teriolecta, and Skeletonema costatum), time-dependent species-sensitivity distributions (SSDs) were derived for different effect sizes. The present study showed that H2O2 can be used effectively to treat ballast water but that relatively high concentrations and long treatment durations are required to eliminate the vast majority of species in ballast water. The described toxicant effectiveness approach using SSDs also has other potential fields of application, including short-term application of biocides.
Chronic sublethal effects associated with branched alkylbenzenes bioaccumulated by mussels
Authors: Scarlett Alan , Rowland Steven J , Galloway Tamara S , Lewis Alistair C , Booth Andy M
Published: February 2008

Crude oils are complex mixtures of many thousands of compounds, both resolved and unresolved by conventional gas chromatography (GC). Recent research using comprehensive two-dimensional gas chromatography–time-of-flight–mass-spectrometry (GC × GC-ToF-MS) identified branched alkylbenzenes (BABs) as a major component of some unresolved complex mixtures of hydrocarbons (UCMs) bioaccumulated in the tissues of North Sea mussels, Mytilus edulis, previously found to have poor health status. Here the effect of long-term exposure to low aqueous concentration of BABs and mussels' ability to recover, was determined. Mussels were exposed to 5 μg/L of a complex mixture of C12–14 BABs for 14 d. Feeding rates and the viability of hemocytes were measured immediately after exposure and again after 5 d depuration. Tissues were extracted, analyzed and alkylbenzenes quantified by both GC-MS and GC × GC-ToF-MS. Mussel extracts from previous acute tests were also reanalyzed and quantified using GC × GC-ToF-MS. Mussels exposed to 5 μg/L BABs for 14 d accumulated 46 to 47 μg/g dry weight alkylbenzenes; this was similar to tissue concentrations of mussels exposed to 41 μg/L for 72 h. Feeding rates were significantly reduced (p ≤ 0.05) and were dependent upon tissue concentration. Cellular viability was not significantly affected. Following 5 d in clean seawater, the BABs were only partially depurated and feeding rates failed to fully recover. The use of GC × GC-ToF-MS in the present study has shown that mussel tissue concentrations of complex mixtures of alkylbenzenes, and their corresponding effects, are consistent with reported concentrations within UCM-contaminated wild mussel populations with poor health status.