Effects Of Environmental Contaminants Research Articles

Toxic effects of environmentally realistic concentrations of diclofenac in organisms from two distinct trophic levels, Hediste diversicolor and Solea senegalensis

The use of pharmaceutical drugs has systematically increased, resulting in their environmental presence and exertion of effects on non-target aquatic organisms. Diclofenac (DCF) is an analgesic, anti-inflammatory and antipyretic drug, frequently found in the aquatic compartment. The present work analyzed the ecotoxicological effects of DCF in the marine polychaete Hediste diversicolor and in the marine fish Solea senegalensis. In addition, the putative toxic effects of DCF along a simulated food chain were studied, by feeding individuals of S. senegalensis with H. diversicolor previously exposed to DCF. Biomarkers of anti-oxidant defense (catalase, CAT), phase II metabolism (glutathione S-transferases, GSTs) and neurotoxicity (acetylcholinesterase, AChE) were quantified. The obtained results demonstrated that DCF did not affect CAT activity in organisms of both species directly exposed through the water, suggesting the absence of oxidative effects. In addition, organisms directly or indirectly exposed to DCF showed an increase of GSTs activities, suggesting an additional challenge to the metabolism of the exposed individuals. However, significant decreases in the activities of CAT and AChE were observed in fish fed with worms previously exposed to DCF. These data suggest that direct or indirect exposure to DCF may cause significant physiological modifications in aquatic organisms. In addition, exposure of wild organisms via contaminated food may lead to toxicological effects which may differ from alterations elicited by direct exposure. Such toxicological differences, between direct (waterborne) and trophic (via contaminated feed) exposures were qualitatively distinct, and need to be fully addressed when considering the consequences of environmental contamination by therapeutic drugs.

Effect of environmental contamination on female and male gametes - A lesson from bovines.

Endocrine-disrupting compounds (EDCs) and foodborne contaminants are environmental pollutants that are considered reproductive toxicants due to their deleterious effects on female and male gametes. Among the EDCs, the phthalate plasticizers are of growing concern. In-vivo and in-vitro models indicate that the oocyte is highly sensitive to phthalates. This review summarizes the effects of di(2-ethylhexyl) phthalate and its major metabolite mono(2-ethyhexyl) phthalate (MEHP) on the oocyte. MEHP reduces the proportion of oocytes that fertilize, cleave and develop to the blastocyst stage. This is associated with negative effects on meiotic progression, and disruption of cortical granules, endoplasmic reticulum and mitochondrial reorganization. MEHP alters mitochondrial membrane polarity, increases reactive oxygen species levels and induces alterations in genes associated with oxidative phosphorylation. A carryover effect from the oocyte to the blastocyst is manifested by alterations in the transcriptomic profile of blastocysts developed from MEHP-treated oocytes. Among foodborne contaminants, the pesticide atrazine (ATZ) and the mycotoxin aflatoxin B1 (AFB1) are of high concern. The potential hazards associated with exposure of spermatozoa to these contaminants and their carryover effect to the blastocyst are described. AFB1 and ATZ reduce spermatozoa's viability, as reflected by a high proportion of cells with damaged plasma membrane; induce acrosome reaction, expressed as damage to the acrosomal membrane; and interfere with mitochondrial function, characterized by hyperpolarization of the membrane. ATZ and AFB1-treated spermatozoa show a high proportion of cells with fragmented DNA. Exposure of spermatozoa to AFB1 and ATZ reduces fertilization and cleavage rates, but not that of blastocyst formation. However, fertilization with AFB1- or ATZ-treated spermatozoa impairs transcript expression in the formed blastocysts, implying a carryover effect. Taken together, the review indicates the risk of exposing farm animals to environmental contaminants, and their deleterious effects on female and male gametes and the developing embryo.

Methods for rearing ground-nesting bees under laboratory conditions

Ground-nesting bees are largely undervalued, both in terms of their use as model species for behavioural studies, and in terms of their agricultural benefit as pollinators in crop systems. But, why? One potential barrier limiting their use as model species may be our understanding of how to effectively establish and maintain ground-nesting bees in the laboratory. Here we review how artificial nests are used to study ground-nesting bees and provide guidelines for building, starting and maintaining artificial nests. Ultimately, appropriate design and maintenance of artificial nests will allow researchers to explore a suite of interesting questions related to this important group of pollinating insects, from natural history to the origins of eusociality and the effects of environmental contaminants.

Wing membrane and fur samples as reliable biological matrices to measure bioaccumulation of metals and metalloids in bats

There is a growing conservation concern about the possible consequences of environmental contamination in the health of bat communities. Most studies on the effects of contaminants in bats have been focused on organic contaminants, and the consequences of bat exposure to metals and metalloids remain largely unknown. The aim of this study was to evaluate the suitability of external biological matrices (fur and wing membrane) for the assessment of exposure and bioaccumulation of metals in bats. The concentration of arsenic, cadmium, cobalt, chromium, copper, manganese, nickel, lead, selenium and zinc was measured in internal organs (liver, heart, brain), internal (bone) and external tissues (wing membrane, fur) collected from bat carcasses of four species (Hypsugo savii, Nyctalus leisleri, Pipistrellus pipistrellus, Pipistrellus pygmaeus) obtained in windfarm mortality searches. With the exception of zinc (P = 0.223), the results showed significant differences between the concentrations of metals in the analyzed tissues for all metals (P < 0.05). Significant differences were also found between organs/tissues (P < 0.001), metals (P < 0.001) and a significant interaction between organs/tissues and metals was found (P < 0.001). Despite these results, the patterns in terms of metal accumulation were similar for all samples. Depending on the metal, the organ/tissue that showed the highest concentrations varied, but fur and wing had the highest concentrations for most metals. The variability obtained in terms of metal concentrations in different tissues highlights the need to define standardized methods capable of being applied in monitoring bat populations worldwide. The results indicate that wing membrane and fur, biological matrices that may be collected from living bats, yield reliable results and may be useful for studies on bats ecotoxicology, coupled to a standardized protocol for large-scale investigation of metal accumulation.

Effects of environmental contaminants in inflammatory bowel disease: a systematic review

Introduction: The Inflammatory Bowel Disease (IBD) is characterized by a chronic inflammation of the gastrointestinal tract and it has two important forms: Crohn’s Disease and Ulcerative Colitis. Although the pathophysiology of the disease is mostly unknown, an interaction between the immune system, genetics, microbiome and environmental factors seems to be responsible for the disease onset. The role of environmental factors in the pathophysiology of this disease is reinforced if we consider the rapid growth in incidence and prevalence rates of IBD in areas where the incidence was previously low as, for example, Asia. However, the literature on the role of environmental factors in IBD is reduced and is not systematized. Hence, in this work a Systematic Review of the literature was performed. Materials and methods: For this systematic review the methodology “Navigation Guide Method for Grading Human Evidence” was used [1]. The research was carried out in three databases (Scopus, Web of Science, PubMed / MEDLINE). The inclusion criteria used were: research articles with original human data, clinically diagnosed inflammatory bowel disease, quantification of environmental contaminants and study of the association between environmental contaminants and inflammatory bowel disease. Only articles written in Portuguese, English, French or Spanish were included. Results: Sixteen studies were included in this systematic review. Of these, 13 studied Inflammatory Bowel Disease in general, 2 studies included only patients with Crohn’s Disease and 1 study included only patients with Ulcerative Colitis. The most studied environmental contaminants were sulfur dioxide, nitrogen dioxide, carbon monoxide, particulate matter (PM), perfluorooctanoic acid, aluminum, iron, zinc, copper, titanium dioxide, silicates and endotoxins. We also identified different categories of studies, 4 studies on the effects of air pollution, 3 on the intake of contaminated water and 3 on the effects of diet. Additionally, 2 studies evaluated the serum concentrations of contaminants, 1 studied the impact of exposure to house dust, 2 attempted a cell characterization of IBD patients and in another colitis was induced. Overall, the quality of evidence was rated “moderate to low” and the strength of evidence as “Inadequate evidence on toxicity”. Discussion and conclusions: In this systematic review, we have identified different classes of environmental contaminants associated with IBD, but studies reporting their concentration in biological matrices are rare. Based on a moderate to low level of quality, the available evidence gathered in this Systematic Review is insufficient to access the role of environmental contaminants in inflammatory bowel disease. New epidemiological studies are necessary.

Sex Determination, Sexual Development, and Sex Change in Slipper Snails.

Sex determination and sexual development are highly diverse and controlled by mechanisms that are extremely labile. While dioecy (separate male and female functions) is the norm for most animals, hermaphroditism (both male and female functions within a single body) is phylogenetically widespread. Much of our current understanding of sexual development comes from a small number of model systems, limiting our ability to make broader conclusions about the evolution of sexual diversity. We present the calyptraeid gastropods as a model for the study of the evolution of sex determination in a sequentially hermaphroditic system. Calyptraeid gastropods, a group of sedentary, filter-feeding marine snails, are sequential hermaphrodites that change sex from male to female during their life span (protandry). This transition includes resorption of the penis and the elaboration of female genitalia, in addition to shifting from production of spermatocytes to oocytes. This transition is typically under environmental control and frequently mediated by social interactions. Males in contact with females delay sex change to transition at larger sizes, while isolated males transition more rapidly andat smaller sizes. This phenomenon has been known for over a century; however, the mechanisms that control the switch from male to female are poorly understood. We review here our current understanding of sexual development and sex determination in the calyptraeid gastropods and other molluscs, highlighting our current understanding of factors implicated in the timing of sex change and the potential mechanisms. We also consider the embryonic origins and earliest expression of the germ line and the effects of environmental contaminants on sexual development.

Towards Salt Marsh Harvest Mouse Recovery: A Review

Author(s): Smith, Katherine R.; Riley, Melissa K.; Barthman–Thompson, Laureen; Woo, Isa; Statham, Mark J.; Estrella, Sarah; Kelt, Douglas A. | Abstract: The salt marsh harvest mouse (SMHM, Reithrodontomys raviventris) is an endangered species, endemic to the San Francisco Estuary. Despite being protected for almost half a century and being included in a large number of recovery, restoration, and management plans, significant data gaps hinder conservation and management of the species, a challenge further complicated by developing threats such as climate change. In this review, we present the current state of knowledge; highlight research gaps on habitat requirements and distribution, taxonomic status and genetic structure, physiology, reproduction and demographics, population dynamics, and behavior and community interactions; and present an overview of threats to the species. Our review indicates that substantial data gaps exist; although some aspects of SMHM ecology, such as habitat use, have been addressed extensively, others, such as the effects of environmental contamination, are largely unaddressed. We suggest that conservation and restoration-planning processes consider experimental approaches within restoration designs to address these deficiencies. Continued investment in basic and applied SMHM ecology to collect baseline and long-term data will also be beneficial. Additionally, further coordination among managers and researchers can facilitate more effective responses to uncertainties and emerging threats, especially climate change, which threatens the SMHM and its habitat throughout its range.

Modeling the seasonality of Methicillin-resistant Staphylococcus aureus infections in hospitals with environmental contamination

ABSTRACTA deterministic mathematical model with periodic antibiotic prescribing rate is constructed to study the seasonality of Methicillin-resistant Staphylococcus aureus (MRSA) infections taking antibiotic exposure and environmental contamination into consideration. The basic reproduction number for the periodic model is calculated under the assumption that there are only uncolonized patients with antibiotic exposure at admission. Sensitivity analysis of with respect to some essential parameters is performed. It is shown that the infection would go to extinction if the basic reproduction number is less than unity and would persist if it is greater than unity. Numerical simulations indicate that environmental cleaning is the most important intervention to control the infection, which emphasizes the effect of environmental contamination in MRSA infections. It is also important to highlight the importance of effective antimicrobial stewardship programmes, increase active screening at admission and subsequent isolation of positive cases, and treat patients quickly and efficiently.

Effects of Environmental Contamination and Acute Toxicity of N-Nitrate on Early Life Stages of Endemic Arboreal Frog, Polypedates cruciger (Blyth, 1852).

This study investigated the potential toxic effects of environmentally relevant nitrate concentrations on development, growth, and mortality of early life stages of common hour-glass tree frog, Polypedates cruciger. Tadpoles from hatchlings through pre-adult were exposed to environmentally relevant nitrate concentrations detected in Mirissa, Sri Lanka. Newly hatched, external gill stage, and internal gill stage tadpoles were exposed to potassium nitrate for bioassay tests. No behavioral changes or abnormalities were observed in control and nitrate-induced group. However, detected environmental nitrate concentration significantly increased (p < 0.05) the growth of the tadpoles up to 25 days old. Results revealed that newly hatched and external gill stage was more susceptible to the nitrate pollution than internal gill stage. The results suggest that environmentally relevant nitrate can cause mortality on the amphibian population in ecosystems associated with agro-pastoral activities through altering the growth and direct toxicological effects on the survivorship.

Water Adsorption and Dissociation on Polycrystalline Copper Oxides: Effects of Environmental Contamination and Experimental Protocol.

We use ambient-pressure X-ray photoelectron spectroscopy (APXPS) to study chemical changes, including hydroxylation and water adsorption, at copper oxide surfaces from ultrahigh vacuum to ambient relative humidities of ∼5%. Polycrystalline CuO and Cu2O surfaces were prepared by selective oxidation of metallic copper foils. For both oxides, hydroxylation occurs readily, even at high-vacuum conditions. Hydroxylation on both oxides plateaus near ∼0.01% relative humidity (RH) at a coverage of ∼1 monolayer. In contrast to previous studies, neither oxide shows significant accumulation of molecular water; rather, both surfaces show a high affinity for adventitious carbon contaminants. Results of isobaric and isothermic experiments are compared, and the strengths and potential drawbacks of each method are discussed. We also provide critical evaluations of the effects of the hot filament of the ion pressure gauge on the reactivity of gas-phase species, the peak fitting procedure on the quantitative analysis of spectra, and rigorous accounting of carbon contamination on data analysis and interpretation. This work underscores the importance of considering experimental design and data analysis protocols during APXPS experiments with water vapor in order to minimize misinterpretations arising from these factors.

The duration of pregnancy in ecologically-challenged area. The effects of environmental pollution with aromatic hydrocarbons on the angiogenesis and elements of the mesenchymal tissue of the human placenta.

The literature presents only few reports regarding the effects of elevated levels of aromatic hydrocarbons (AH) on the functions of the human placenta. The effects of environmental contamination with AH (including phenol and 1-hydroxypyrene) have certain negative effects on parenchymal organs such as human placenta. The paper aimed to assess the effects of elevated levels of AH on the placental angiogenesis and elements of the mesenchymal tissue of the placenta. Tissue material from 50 afterbirths from Płock constituted a study group, whereas 50 afterbirths from Kutno constituted a control group. Immunohistochemical reactions with the peroxidase method using LSAB kits (DAKO) were performed. The extent and intensity of reactions were analysed. The levels of phenols and 1-hydroxypyrene in the excreted urine of pregnant women (undergoing delivery) were detected using gas chromatography and colorimetry. The levels of phenol and 1-hydroxypyrene in the excreted urine were demonstrated to be statistically significantly higher in patients living in the area of Płock. Statistically significantly higher expression of antibodies indicating placental angiogenesis was observed in the placentas in the Płock group (p < 0.01). Moreover, lower expression of vimentin indicating reactions with proteins in mesenchymal cells was observed in the Kutno group (p < 0.01). Pregnancy in the environment with elevated levels of aromatic hydrocarbons has detrimental effects on the human placenta. The foetus is protected by activation of adaptation and compensation mechanisms that are manifested as significant angiogenesis and greater development and differentiation of mesenchymal cells compared to the control group.

Screening for Cd-Safe Cultivars of Chinese Cabbage and a Preliminary Study on the Mechanisms of Cd Accumulation.

With the rapid progress of industrialization, the effects of environmental contamination on plant toxicity, and subsequently on human health, is a growing concern. For example, the heavy metal pollution of soil such as that caused by cadmium (Cd) is a serious threat. Therefore, screening for pollution-safe edible plants is an essential approach for growing plants under heavy metal-contaminated soils. In the current study, 35 Chinese cabbage (Brassica pekinensis L.) cultivars were selected with the aim of screening for Cd-safe cultivars (CSCs), analyzing their safety, and exploring the mechanism of Cd accumulation. Our field-culture experiments revealed that the Cd content in the edible parts of the cultivars were varied and were determined to possibly be CSCs. Hydroponics experiments were used to simulate six different degrees of soil contamination (high and low Cd concentrations) on possible CSCs. The results indicated a significant difference (p < 0.05) in Cd concentration in the cultivars, and verified the safety of these possible CSCs. The analyses of the transport coefficient and expression levels showed that the differences in Cd accumulation among the Chinese cabbage cultivars were related to the expression of genes involved in absorption and transport rather than a root-to-shoot translocation limitation.

Use of Gammarus fossarum (Amphipoda) embryo for toxicity testing: A case study with cadmium.

The effects of environmental contaminants on arthropod embryo stages have been poorly investigated in ecotoxicology. Moreover, many of these tests used hatching success as the sole metric, although it is possible to detect many more subtle effects. After a detailed description of embryogenesis in Gammarus fossarum, the present study reports on the sublethal effects of cadmium (Cd) exposure during embryonic development in G. fossarum. Embryos were first directly exposed in multiwell plates throughout the entire embryonic cycle (23 d) to increasing Cd concentrations (0, 1.5, and 3.0 μg/L; 120 embryos/concentration). Then, to assess the representativeness of the gammarid embryo assay performed in multiwell plates, embryos were exposed to similar Cd concentrations through the maternal open brood pouch. Next, to pinpoint sensitive periods of development, embryos were directly exposed to 3.0 μg/L of Cd for shorter periods of time: during gastrulation, organogenesis, and hatching. After hatching, the following parameters were measured in the newborn individuals: 1) body mass; 2) activity of the enzyme phenoloxidase, a key enzyme of the arthropod immune system; and 3) locomotor activity. Phenoloxidase activity was strongly inhibited in newborn individuals of embryos exposed (either in multiwell plates or in the maternal brood pouch) to 3.0 μg/L Cd throughout embryonic development. Furthermore, strong detrimental locomotor effects were observed in newborn individuals of embryos directly exposed to 3.0 μg/L. Exposures for shorter periods of time were not sufficient to induce such effects; no sensitive period could be determined. By bringing new insights into a critical time window of exposure, the gammarid embryo assay could provide a novel and interesting addition to existing bioassays in gammarids. Environ Toxicol Chem 2017;36:2436-2443. © 2017 SETAC.

Modernizing Water Quality Criteria in the United States: A Need to Expand the Definition of Acceptable Data.

The development of water quality criteria (WQC) for the protection of aquatic life is a fundamental component of the Clean Water Act-the primary US legislation responsible for protecting aquatic ecosystems from pollution. Water quality criteria define acceptable levels of contamination in the environment and thus play an important role in society. Rules for how science is used to develop WQC were created in 1985. Most rely on only data and knowledge obtained through a single methodology, the single-species laboratory toxicity test. Since 1985, understanding of the fate and effects of environmental contaminants has advanced markedly from multiple perspectives and disciplines. However, many of these advances are routinely discarded in WQC development because they do not adhere to data limits imposed by the 1985 guidelines. The present Focus article outlines how multiple lines of inquiry have played important roles in improving understanding of the ecological implications of environmental contaminants. The authors focus on gains in understanding that would not have been possible through traditional toxicity bioassays alone and argue that more robust scientific understanding can be used to modernize WQC development. In particular, the present article highlights ways to increase the relevance of toxicity testing (at different spatiotemporal scales) and incorporate all relevant lines of evidence into WQC modernization. Environ Toxicol Chem 2017;36:285-291. © 2017 SETAC.

Off-site impacts of wildfires on aquatic systems - Biomarker responses of the mosquitofish Gambusia holbrooki.

The number of wildfires has markedly increased in Mediterranean Europe, including in Portugal. Wildfires are environmentally concerning, not only due to the loss of biodiversity and forest area, but also as a consequence of environmental contamination by specific compounds including metals and polycyclic aromatic compounds (PAHs). These contaminants, mostly bound to ashes, can reach downstream water bodies, namely through surface runoff, being ultimately dispersed by vast areas and contacting with aquatic biota. Being toxicologically noteworthy, the potential toxic outcomes of the input of such chemicals across the aquatic compartment must be characterized. In this context, the present study used a biomarker-based approach to find early-warning signals of toxicity triggered by the exposure of the mosquitofish, Gambusia holbrooki, to affected aqueous runoff and stream water samples collected from a forest burnt area. The chemical analysis revealed concerning levels of metals and polycyclic aromatic hydrocarbons in both runoff and stream water samples. Biological responses elicited by the collected samples showed the occurrence of pro-oxidative modifications, specifically driven by enzymatic forms involved in the metabolism of glutathione. Despite these effects, no further signs of involvement of metals and PAHs were elicited in terms of neurotoxicity. The overall set of data implicates chemicals resulting from wildfires in clear deleterious effects in exposed fish.

Impaired growth and reproductive capacity in marine rockweeds following prolonged environmental contaminant exposure

AbstractIntertidal macroalgae are resilient organisms, withstanding daily fluctuations in temperature, salinity and air exposure. These sessile seaweeds are exposed to anthropogenic pollution as an additional stressor in their natural habitat alongside coastal waterways, which are often adjacent to industrial centers. One such habitat in the New Bedford Harbor in Massachusetts has been recognized by government agencies as a site of National Priority after several decades of polychlorinated biphenyl and metal discharge. Research has focused on the effects of these contaminants among large-scale trophic cascades, with less emphasis on sessile primary productivity. Macroalgal members of the community were the focus of this study and were used to evaluate the presence and effect of environmental contaminants. Contaminants prominent in highly polluted regions of the harbor were elevated in tissue samples. Field surveys evaluating density and biomass were conducted in five areas of varying contamination and indicated a drastic inhibition of colonization with increasing contaminant load. No differences were detected between sites in terms of oocyte production in a single receptacle, but only individuals from less contaminated regions released those oocytes. Potential causes of decreased population size may therefore be reduction in individual biomass and a decreased ability to release eggs.

The effect of environmental contamination on the community structure and fructification of ectomycorrhizal fungi.

Ectomycorrhizal fungi are an essential component of forest ecosystems, most of which can form edible and medical fruiting bodies. Although many studies have focused on the fructification of ectomycorrhizal fungi in phenology, the impact of environmental contamination, especially living garbage, on the formation of fruiting body is still unknown. A field investigation, combined with a high‐throughput sequencing method, was used to study the effect of living garbage pollution on the fructification and hypogeous community structure of ectomycorrhizal fungi symbiosing with cedar (Cedrus deodara (Roxb.) G. Don). The results showed that garbage significantly altered soil abiotic and biotic properties, increasing soil urease activity, decreasing the soil exchangeable metal content and phosphatase activity, and ultimately inhibiting the formation of fruiting bodies. The pollution of garbage also changed the community structure of hypogeous ectomycorrhizal fungi where ectomycorrhizal ascomycetes dominated. In unpolluted sites, the relative abundance of ectomycorrhizal ascomycetes and basidiomycetes were almost equal. Although no fruiting bodies were observed in that soil polluted by living garbage, the sequencing result showed that various ectomycorrhizal fungi were present underground, suggesting that these taxonomic fungi had the potential to cope with adverse conditions. This study not only provided a deeper understanding of the relationship between ectomycorrhizal fungal communities and prevailing environmental conditions, but provided a new pathway for the excavation and utilization of the resource of antistress ectomycorrhizal fungi.

Short-Term Exposure to Coal Combustion Waste Has Little Impact on the Skin Microbiome of Adult Spring Peepers (Pseudacris crucifer).

Disruptions to the microbiome can impact host health as can exposure to environmental contaminants. However, few studies have addressed how environmental contaminants impact the microbiome. We explored this question for frogs that breed in wetlands contaminated with fly ash, a by-product of coal combustion that is enriched in trace elements. We found differences in the bacterial communities among a fly ash-contaminated site and several reference wetlands. We then experimentally assessed the impacts of fly ash on the skin microbiome of adult spring peepers (Pseudacris crucifer). Frogs were exposed to fly ash in the laboratory for 12 h, the duration of a typical breeding event, and the skin microbiome was assessed after 5 days (experiment 1) or after 5 and 15 days (experiment 2). We examined bacterial community structure using 16S rRNA gene amplicon sequencing and metabolite profiles using high-pressure liquid chromatography-mass spectrometry (HPLC-MS). We found little impact as the result of acute exposure to fly ash on the bacterial communities or metabolite profiles in either experiment, suggesting that the bacterial symbiont communities of adults may be relatively resistant to brief contaminant exposure. However, housing frogs in the laboratory altered bacterial community structure in the two experiments, which supports prior research suggesting that environmental source pools are important for maintaining the amphibian skin microbiome. Therefore, for contaminants like fly ash that may alter the potential source pool of symbionts, we think it may be important to explore how contaminants affect the initial assembly of the amphibian skin microbiome in larval amphibians that develop within contaminated sites. Animals are hosts to many symbiotic microorganisms, collectively called the microbiome, that play critical roles in host health. Therefore, environmental contaminants that alter the microbiome may impact hosts. Some of the most widespread contaminants, produced worldwide, are derived from the mining, storage, and combustion of coal for energy. Fly ash, for example, is a by-product of coal combustion. It contains compounds such as arsenic, selenium, cadmium, and strontium and is a recognized source of ground and surface water contamination. Here, we experimentally investigated the impacts of short-term fly ash exposure on the skin microbiome of spring peepers, one of many species of amphibian that sometimes breed in open fly ash disposal ponds. This research provides a look into the potential impacts of fly ash on an animal's microbiome and suggests important future directions for research on the effects of environmental contaminants on the microbiome.

Identification of Putative Nuclear Receptors and Steroidogenic Enzymes in Murray-Darling Rainbowfish (Melanotaenia fluviatilis) Using RNA-Seq and De Novo Transcriptome Assembly

Murray-Darling rainbowfish (Melanotaenia fluviatilis [Castelnau, 1878]; Atheriniformes: Melanotaeniidae) is a small-bodied teleost currently under development in Australasia as a test species for aquatic toxicological studies. To date, efforts towards the development of molecular biomarkers of contaminant exposure have been hindered by the lack of available sequence data. To address this, we sequenced messenger RNA from brain, liver and gonads of mature male and female fish and generated a high-quality draft transcriptome using a de novo assembly approach. 149,742 clusters of putative transcripts were obtained, encompassing 43,841 non-redundant protein-coding regions. Deduced amino acid sequences were annotated by functional inference based on similarity with sequences from manually curated protein sequence databases. The draft assembly contained protein-coding regions homologous to 95.7% of the complete cohort of predicted proteins from the taxonomically related species, Oryzias latipes (Japanese medaka). The mean length of rainbowfish protein-coding sequences relative to their medaka homologues was 92.1%, indicating that despite the limited number of tissues sampled a large proportion of the total expected number of protein-coding genes was captured in the study. Because of our interest in the effects of environmental contaminants on endocrine pathways, we manually curated subsets of coding regions for putative nuclear receptors and steroidogenic enzymes in the rainbowfish transcriptome, revealing 61 candidate nuclear receptors encompassing all known subfamilies, and 41 putative steroidogenic enzymes representing all major steroidogenic enzymes occurring in teleosts. The transcriptome presented here will be a valuable resource for researchers interested in biomarker development, protein structure and function, and contaminant-response genomics in Murray-Darling rainbowfish.

The effect of environmental contamination on the decomposition of European frog-bit (Hydrocharis morsus-ranae L.) in natural conditions

Decomposition is one of the fundamental processes that influence the recycling of elements in the ecosystem. Environmental pollution and eutrophication may affect plant decay and, therefore, lead to disturbances in detritus-based food webs. The objective of the study has been to describe changes in biomass loss and macroelements (C, Ca, K, Mg, N, Na, P, S) and trace metals (Cd, Cr, Cu, Fe, Mn, Ni, Pb, Zn) contents during breakdown of Hydrocharis morsus-ranae L. (European frog-bit). The questions underlying the study were: Does element concentration in plant litter or the environment affect the rate and pattern of H. morsus-ranae decomposition? What are the chemical predictors of the H. morsus-ranae detritus decay rate? An in situ experiment on decomposition was conducted using the litter-bag technique. H. morsus-ranae was found to be a fast decomposing macrophyte. The Na, Mn and K release rates were the largest, and the concentrations of C, N, P, S and trace metals in litter increased during the decay. In study sites that differed in element concentrations in fresh plant material and water plants had different decay rates and final element contents. Both the inhibitory effect of contaminants (Cd and Ni) and/or stimulatory effect of nutrients (P, N) and essential elements, such as Fe, Mg and Mn, could cause variation in decomposition observed between the study sites.