Field exposure of frog embryos and tadpoles along a pollution gradient in the Fox River and Green Bay ecosystem in Wisconsin, Usa

Levels of persistent organic pollutants in cane toads (Rhinella marina) differ among sites with varying industrial and agricultural activities

In this study, we captured cane toads (Rhinella marina) in four sites located in different regions affected by anthropogenic activities in Mexico. Subsequently we analyzed liver tissue for the presence of organochlorine pesticides (OCs) and polychlorinated biphenyls (PCBs) The levels of these POPs in the toads' livers ranged from 863.2 to 3109.6 ng/g of lipid weight across all sites. A multivariate statistical analysis highlighted two sites with the highest POPs levels, with the most polluted site displaying a high level of PCBs, suggesting influence of industrial activities. The second most polluted site displayed significant amounts of OCs, linking this location to agricultural activity. Additionally, we found pesticide metabolites and isomers that allowed us to distinguish past and recent exposure events. Our observations indicate that R. marina is suitable bioindicator of sites impacted by anthropogenic activities.

A review of non-destructive biomonitoring techniques to assess the impacts of pollution on reproductive health in frogs and toads

In anuran amphibians (frogs and toads), evidence linking pollution to population declines is limited, in particular through impaired reproduction. Here we review the evidence for pollutant-induced alterations on reproductive endpoints in wild anurans with a particular focus on the application of non-destructive endpoints including on sex ratios, male reproductive phenotypes (data are too scarce for females) and reproductive outputs (reflective of mating success). Data evidencing alterations in sex ratio in wild anurans are scarce, however, both feminisation and masculinisation in response to pollution have been reported (seven studies). Male nuptial pad morphology and calling behaviour display high sensitivity to pollutant-exposure and are important features determining male breeding success, however there is considerable variation in these endpoints and inconsistencies in the responses of them to pollution are reported in wild anurans. Data for clutch size are insufficient to assess sensitivity to pollutants (five studies only). However, hatch success and offspring fitness (tadpole survival/development) are sensitive to pollution, with clear linkages to population stability. In conclusion, there are a wide range of non destructive measures with good potential for application to assess/monitor reproductive health in wild anurans, however, a greater understanding of pollutant effects on these endpoints is needed. There measures deserve wider application as they are relatively simple and inexpensive to implement, and as they can be applied non-destructively are widely applicable to our declining anuran populations.

Larval Exposure to Polychlorinated Biphenyl-126 Led to a Long-Lasting Decrease in Immune Function in Postmetamorphic Juvenile Northern Leopard Frogs, Lithobates pipiens

Amphibian populations are decreasing worldwide, and pollution is a contributing factor. Polychlorinated biphenyls (PCBs) are a class of persistent organic pollutants known to exert immunotoxicity. To assess impacts of PCBs on frogs, we exposed Lithobates pipiens tadpoles to a diet of PCB-126 (0-5 ng PCB-126/g wet food) through metamorphic climax. Postmetamorphic frogs were immunized with keyhole limpet hemocyanin (KLH); then production of KLH-specific IgY, as well as total IgY and IgM, was measured (Trial I). A second larval study (0 and 7.3 ng PCB-126/g wet food) was performed to investigate whether PCB altered antigenic responses in prometamorphic tadpoles (Gosner Stage 36-39), and to measure the innate immune response of postmetamorphic frogs (Trial II). After larval PCB-126 exposure, both KLH-specific IgY levels and complement activity were reduced. Because postmetamorphic frogs carried a body burden of PCB-126 (2.4 ng/g or less), we wanted to determine whether the effect on immune response was due to larval exposure or to the resulting body burden as frogs. To test this, we reared tadpoles under control conditions (no PCB), and limited PCB exposure to postmetamorphosis only by injecting 2-week-old frogs with 10 ng PCB-126/g (Trial III). The resulting body burden (3.4 ng/g) was similar to that of frogs in Trial I, but we no longer detected suppression of KLH-specific IgY or hemolytic activity. These results suggest life-stage-specific immune responses; however, because we administered PCB-126 differently between trials, it is premature to conclude that these differences are intrinsically life stage dependent, and further study is warranted. Regardless, our study demonstrated a long-lasting effect of larval PCB-126 exposure that persisted through metamorphosis and suppressed frog immunity. Environ Toxicol Chem 2022;41:81-94. © 2021 SETAC.

Warmer temperature increases toxicokinetic elimination of PCBs and PBDEs in Northern leopard frog larvae (Lithobates pipiens)

We studied the temperature dependence of accumulation and elimination of two polychlorinated biphenyls (PCBs; PCB-70 and PCB-126) and a commercial mixture of congeners of polybrominated diphenyl ethers (PBDEs; DE-71™)) in Northern leopard frog (Lithobates pipiens) tadpoles. We reared tadpoles at 18, 23, or 27 °C for 5.3 or up to 13.6 weeks (longer at cooler temperature where development is slower) on diets containing the toxicants, each at several different toxicant concentrations, and compared tissue concentrations as a function of food concentration and rearing temperature. Following > 1 month of accumulation, tissue concentrations of all three toxicants in exposed tadpoles were linearly related to dietary concentrations as expected for first order kinetics, with no significant effect of rearing temperature.We also raised free-swimming L. pipiens tadpoles for 14 days on foods containing either toxicant at 18 or 27 °C during an accumulation phase, and then during depuration (declining toxicant) phase of 14 days we provided food without toxicants and measured the decline of toxicants in tadpole tissue. All the congeners were eliminated faster at warmer rearing temperature, as expected. Using Arrhenius' equation, we calculated that the apparent activation energy for elimination of both PCB congeners by tadpoles was 1.21 eV (95% confidence interval 0.6-1.8 eV). We discuss how this value was within the range of estimates for metabolic reactions generally (range 0.2 - 1.2 eV), which might include metabolic pathways for biotransformation and elimination of PCBs. Furthermore, we discuss how the lack of an effect of rearing temperature on tadpole near-steady-state tissue residue levels suggests that faster elimination at the warmer temperature was balanced by faster uptake, which is plausible considering the similar temperature sensitivities (i.e., activation energies) of all these processes. Although interactions between toxicants and temperature can be complex and likely toxicant-dependent, it is plausible that patterns observed in tadpoles might apply to other aquatic organisms. Published data on depuration in 11 fish species eliminating 8 other organic toxicants indicated that they also had similar apparent activation energy for elimination (0.82 ± 0.12 eV; 95% confidence interval 0.56 - 1.08 eV), even though none of those studied toxicants were PCBs or PBDEs. Additional research on toxicant-temperature interactions can help improve our ability to predict toxicant bioaccumulation in warming climate scenarios.

Extreme Arsenic and Antimony Uptake and Tolerance in Toad Tadpoles during Development in Highly Contaminated Wetlands

The effects of extreme concentrations of toxic metalloids, such as arsenic (As) and antimony (Sb), on larval amphibians are not well-understood. We sampled Western Toad tadpoles (Anaxyrus boreas) living in As- and Sb-contaminated wetlands throughout their development. Although the tadpoles completed metamorphosis, they accumulated among the highest concentrations of As and Sb ever reported for a living vertebrate (3866.9 mg/kg; 315.0 mg/kg (dry weight), respectively). Ingestion of contaminated sediment had a more important role in metalloid accumulation than aqueous exposure alone. Metalloids were initially concentrated in the gut; however, by metamorphosis, the majority were found in other tissues. These concentrations subsequently decreased with the onset of metamorphosis, yet remained quite elevated. Sublethal effects, including delayed development and reduced size at metamorphosis, were associated with elevated metalloid exposure. The presence of organic arsenicals in tadpole tissues suggests they have the ability to biomethylate inorganic As compounds. The arsenical trimethyl arsine oxide accounted for the majority of extractable organic As, with lesser amounts of monomethylarsonic acid and dimethylarsinic acid. Our findings demonstrate remarkable tolerance of toad tadpoles to extreme metalloid exposure and implicate physiological processes mediating that tolerance.

Absence of PCB Hot Spot Effect in Walleye Sander vitreus from Lower Green Bay of Lake Michigan

Under certain conditions, polychlorinated biphenyl (PCB) concentration in individuals of one sex of an adult fish population may exceed that of the other sex by more than a factor of two. This phenomenon, known as the PCB hot spot effect, has been postulated to be contingent upon the following two conditions: (1) presence of a PCB hot spot in the bottom sediments of the aquatic ecosystem, such that prey PCB concentrations in the hot spot region are substantially higher than prey PCB concentrations in locations distant from the hot spot, and (2) habitat use varying between the sexes, such that individuals of one sex inhabit the hot spot region to a considerably greater degree than individuals of the other sex. To test whether PCB concentrations in walleye Sander vitreus from lower Green Bay of Lake Michigan displayed a PCB hot spot effect, whole-fish PCB concentrations were determined in ten female and ten male adult walleye from the population spawning in the Fox River, the main tributary to lower Green Bay. In addition, mark-recapture data for the Fox River walleye population were analyzed to determine differences in spatial distributions between the sexes. Results revealed that the ratio of mean PCB concentration in males to mean PCB concentration in females was only 1.13, indicating the absence of a PCB hot spot effect. This result was corroborated by the mark-recapture data analysis, which showed no significant difference in habitat use between the sexes. Thus, although condition 1 was met, condition 2 was not met. Consequently, the PCB hot spot effect was not observed in the Fox River walleye population. Lack of a significant difference in PCB congener distributions between the sexes further corroborated our conclusions.

Widespread legacy brine contamination from oil production reduces survival of chorus frog larvae

Advances in drilling techniques have facilitated a rapid increase in hydrocarbon extraction from energy shales, including the Williston Basin in central North America. This area overlaps with the Prairie Pothole Region, a region densely populated with wetlands that provide numerous ecosystem services. Historical (legacy) disposal practices often released saline co-produced waters (brines) with high chloride concentrations, affecting wetland water quality directly or persisting in sediments. Despite the potential threat of brine contamination to aquatic habitats, there has been little research into its ecological effects. We capitalized on a gradient of legacy brine-contaminated wetlands in northeast Montana to conduct laboratory experiments to assess variation in survival of larval Boreal Chorus Frogs (Pseudacris maculata) reared on sediments from 3 local wetlands and a control source. To help provide environmental context for the experiment, we also measured chloride concentrations in 6 brine-contaminated wetlands in our study area, including the 2 contaminated sites used for sediment exposures. Survival of frog larvae during 46- and 55-day experiments differed by up to 88% among sediment sources (Site Model) and was negatively correlated with potential chloride exposure (Chloride Model). Five of the 6 contaminated wetlands exceeded the U.S. EPA acute benchmark for chloride in freshwater (860 mg/L) and all exceeded the chronic benchmark (230 mg/L). However, the Wetland Site model explained more variation in survival than the Chloride Model, suggesting that chloride concentration alone does not fully reflect the threat of contamination to aquatic species. Because the profiles of brine-contaminated sediments are complex, further surveys and experiments are needed across a broad range of conditions, especially where restoration or remediation actions have reduced brine-contamination. Information provided by this study can help quantify potential ecological threats and help land managers prioritize conservation strategies as part of responsible and sustainable energy development.

Arsenic absorption and excretion in chronically exposed developing toad Rhinella arenarum

We assessed the toxicodynamics of As in developing Rhinella arenarum toad embryos and larvae exposed from fertilization to 0.01-10mgAsL^-1. We determined As content in toad embryos and larvae by X-ray fluorescence spectrometry. Toad embryos and larvae actively bioaccumulated As, reaching tissue concentrations more than one-thousand higher than control levels after 23d-exposure to 10mgAsL^-1. The bioconcentration factors also increased up to fifty times higher levels in toad larvae respect to media levels. Once recovered in As-free media, the larvae rapidly excreted the bioaccumulated As with a half-life of 1.6d. By calcein transport competition assays, we infer that As is excreted through ABCC-like transporters, probably conjugated with GSH. These results are relevant for comprehending the risks posed by As exposure in this autochthonous aquatic species that develops in water courses from Argentina, that may contain As levels ranging between 10-15,000μgL^-1.

Latin American protected areas: Protected from chemical pollution?

Protected areas (PAs) are critically important means to preserve species and maintain natural ecosystems. However, the potential impacts of chemical pollution on PAs are seldom mentioned in the scientific literature. Research on the extent of the occurrence of chemical pollution inside PAs and in-depth assessments of how chemical contaminants may adversely affect the maintenance of species abundance, species survival, and ecosystem functions are scarce to nonexistent. We investigated 1) the occurrence of chemical contaminants inside 119 PAs in Latin America from publically available databases, and 2) reviewed case studies of chemical contaminants and pollution in 4 Latin American PAs. Cases of chemical pollution and contamination inside Latin American PAs mostly originated from sources such as mining, oil, and gas extraction. To date, the focus of the research on chemical pollution research inside Latin American PAs has been primarily on the detection of contamination, typically limited to trace metals. Where management actions have occurred, they have been reactive rather than proactive. Protected areas established in wetlands are the most affected by chemical pollution. Based on the information from the pollution and/or contamination occurrence and the case studies analyzed, Latin American PAs are not well safeguarded from chemical pollution, resulting in both challenges and opportunities to conserve biodiversity and ecosystems. Integr Environ Assess Manag 2017;13:360-370. © 2016 SETAC.

Copper and nickel effects on survival and growth of northern leopard frog (Lithobates pipiens) tadpoles in field-collected smelting effluent water

Trace metals can have subtle yet chronic impacts on organisms by inducing physiological stress that reduces their survival or impedes their ability to tolerate additional environmental stressors. The toxicity literature indicates, however, that aquatic organisms react differently to trace metals depending on the environments in which they reside. The objective of the present study was to understand the response of northern leopard frog (Lithobates pipiens) larvae to ionic copper (Cu), nickel (Ni), and their combination within an effluent water collected downstream of a tailings wetland area. Tadpoles were assigned randomly to 1 of 8 Cu concentrations (8-200 μg/L), 7 Ni concentrations (160-1200 μg/L), or 8 Cu and Ni combined concentrations (8:160-200:1200 μg/L) and showed significant differences in survival and life history traits among treatments. In the Cu and Cu and Ni combined treatments, tadpole survival decreased with increased Cu exposure starting at Cu = 160 μg/L and in the Ni treatment, tadpole survival decreased with increased Ni exposure starting at Ni = 650 μg/L. All Cu-exposed treatments induced a growth increase as the concentration increased, whereas the tadpoles showed a significant decrease in growth rate in Ni treatments. These contrasting outcomes suggest a plastic response to trace metals whereby tadpoles allocate energy reserves toward either escaping or coping with stress. Finally, the authors' argue that future studies will benefit from examining the impacts of multiple stressors in aquatic ecosystems to provide better environmental mitigation.

Mining-caused changes to habitat structure affect amphibian and reptile population ecology more than metal pollution

Emissions from smelting not only contaminate water and soil with metals, but also induce extensive forest dieback and changes in resource availability and microclimate. The relative effects of such co-occurring stressors are often unknown, but this information is imperative in developing targeted restoration strategies. We assessed the role and relative effects of structural alterations of terrestrial habitat and metal pollution caused by century-long smelting operations on amphibian and reptile communities by collecting environmental and time- and area-standardized multivariate abundance data along three spatially replicated impact gradients. Overall, species richness, diversity, and abundance declined progressively with increasing levels of metals (As, Cu, and Ni) and soil temperature (T(s)) and decreasing canopy cover, amount of coarse woody debris (CWD), and relative humidity (RH). The composite habitat variable (which included canopy cover, CWD, T(s), and RH) was more strongly associated with most response metrics than the composite metal variable (As, Cu, and Ni), and canopy cover alone explained 19-74% of the variance. Moreover, species that use terrestrial habitat for specific behaviors (e.g., hibernation, dispersal), especially forest-dependent species, were more severely affected than largely aquatic species. These results suggest that structural alterations of terrestrial habitat and concomitant changes in the resource availability and microclimate have stronger effects than metal pollution per se. Furthermore, much of the variation in response metrics was explained by the joint action of several environmental variables, implying synergistic effects (e.g., exacerbation of metal toxicity by elevated temperatures in sites with reduced canopy cover). We thus argue that the restoration of terrestrial habitat conditions is a key to successful recovery of herpetofauna communities in smelting-altered landscapes.

Microevolution due to pollution in amphibians: A review on the genetic erosion hypothesis

The loss of genetic diversity, due to exposure to chemical contamination (genetic erosion), is a major threat to population viability. Genetic erosion is the loss of genetic variation: the loss of alleles determining the value of a specific trait or set of traits. Almost a third of the known amphibian species is considered to be endangered and a decrease of genetic variability can push them to the verge of extinction. This review indicates that loss of genetic variation due to chemical contamination has effects on: 1) fitness, 2) environmental plasticity, 3) co-tolerance mechanisms, 4) trade-off mechanisms, and 5) tolerance to pathogens in amphibian populations.

Distribution and accumulation of metals in tadpoles inhabiting the metalliferous streams of eastern Chalkidiki, northeast Greece

The present study investigates the accumulation of heavy metals [copper (Cu), lead (Pb), zinc (Zn), magnesium (Mn), cadmium (Cd), nickel (Ni), and chromium (Cr)] in tadpoles inhabiting the metalliferous streams flowing within the Asprolakkas River basin (northeast Chalkidiki peninsula, Greece) and the effect of potentially harmful elements in stream water and sediment on the corresponding levels in their tissue. Animals were collected from six sampling sites influenced by a wide range of surface water and stream sediment trace element concentrations. The results of the chemical analyses showed that tadpoles accumulated significant levels of all of the examined metals. The range of whole-body mean measured concentrations were (in dry mass) as follows: Cu (46-182 mg/kg), Pb (103-4,490 mg/kg), Zn (494-11,460 mg/kg), Mn (1,620-13,310 mg/kg), Cd (1.2-82 mg/kg), Ni (57-163 mg/kg), and Cr (38-272 mg/kg). The mean concentrations of Pb, Zn, Mn, Ni, Cr, and Cd in Kokkinolakkas stream, which drains a currently active mining area, were the highest ever reported in tadpoles. Our results indicate that whole-body levels of Pb, Zn, Cu, and Cd increase with stream sediment concentrations and that these organisms tend to accumulate metals bound to Fe and Mn oxides. In addition, high dissolved concentrations and significant concentrations associated with more labile geochemical phases of sediments for specific metals were contributing factors determining whole-body levels. Given the observed bioconcentration factors, as well as the correlation with sediment concentrations, it is proposed that these organisms could be considered as bioindicators of environmental contamination and may be used for monitoring purposes within this metal-rich zone and, perhaps, within other rivers affected by metal mining.

Mercury in tadpoles collected from remote alpine sites in the southern Sierra Nevada mountains, California, USA

Amphibians in alpine wetlands of the Sierra Nevada mountains comprise key components of an aquatic-terrestrial food chain, and mercury contamination is a concern because concentrations in fish from this region exceed thresholds of risk to piscivorous wildlife. Total mercury concentrations were measured in whole tadpoles of the Sierra chorus frog, Pseudacris sierra, two times at 27 sites from high elevations (2786-3375 m) in the southern Sierra Nevada. Median mercury concentrations were 14 ng/g wet weight (154 ng/g dry weight), which were generally low in comparison to tadpoles of 15 other species/location combinations from studies that represented both highly contaminated and minimally contaminated sites. Mercury concentrations in P. sierra were below concentrations known to be harmful in premetamorphic tadpoles of another species and below threshold concentrations for risk to predaceous wildlife. Concentrations in tadpoles were also lower than those observed in predaceous fish in the study region presumably because tadpoles in the present study were much younger (1-2 months) than fish in the other study (3-10 years), and tadpoles represent a lower trophic level than these fish. Mercury concentrations were not related to distance from the adjacent San Joaquin Valley, a source of agricultural and industrial pollutants.

Agricultural intensity in ovo affects growth, metamorphic development and sexual differentiation in the common toad (Bufo bufo)

Pollution was cited by the Global Amphibian Assessment to be the second most important cause of amphibian decline worldwide, however, the effects of the agricultural environment on amphibians are not well understood. In this study, spawn from Bufo bufo was taken from four sites in England and Wales with varying intensities of arable agriculture. Spawn was either placed in tanks containing aged tap water (ex-situ, five replicates) or in cages at the native site (caged, five replicates). Hatching success, abnormal tadpoles, and forelimb emergence were recorded during the larval stage. Individuals were also sampled at five time points (TP) during development (5-, 7-, 9-, 12-, 15-weeks post-hatch) and analysed for morphological parameters. The thyroids (TP2) and the gonads (TP3,4,5) were also analysed histologically. With the exception of the thyroid histopathology, all analysed endpoints were significantly different between ex-situ individuals reared under identical conditions from the different sites. In addition, intensity of arable agriculture had a negative effect on growth and development. At one site, despite distinct rearing conditions, a high level of intersex (up to 42%) and similar sex ratios were observed in both ex-situ and caged individuals. Taken together, these data suggest that maternal exposure and/or events in ovo had a much larger effect on growth, metamorphic development, and sexual differentiation in B. bufo than the ambient environment. This could have important implications for traditional exposure scenarios that typically begin at the larval stage. Intersex is reported for the first time in European amphibians in situ, highlighting the potential use of distinct populations of amphibians in fundamental research into the aetiology of specific developmental effects in wild amphibians.

ICRP Publication 114. Environmental protection: transfer parameters for reference animals and plants

In Publication 103 (ICRP, 2007), the Commission included a section on the protection of the environment, and indicated that it would be further developing its approach to this difficult subject by way of a set of Reference Animals and Plants (RAPs) as the basis for relating exposure to dose, and dose to radiation effects, for different types of animals and plants. Subsequently, a set of 12 RAPs has been described in some detail (ICRP, 2008), particularly with regard to estimation of the doses received by them, at a whole-body level, in relation to internal and external radionuclide concentrations; and what is known about the effects of radiation on such types of animals and plants. A set of dose conversion factors for all of the RAPs has been derived, and the resultant dose rates can be compared with evaluations of the effects of dose rates using derived consideration reference levels (DCRLs). Each DCRL constitutes a band of dose rates for each RAP within which there is likely to be some chance of the occurrence of deleterious effects. Site-specific data on Representative Organisms (i.e. organisms of specific interest for an assessment) can then be compared with such values and used as a basis for decision making. It is intended that the Commission's approach to protection of the environment be applied to all exposure situations. In some situations, the relevant radionuclide concentrations can be measured directly, but this is not always possible or feasible. In such cases, modelling techniques are used to estimate the radionuclide concentrations. This report is an initial step in addressing the needs of such modelling techniques. After briefly reviewing the basic factors relating to the accumulation of radionuclides by different types of biota, in different habitats, and at different stages in the life cycle, this report focuses on the approaches used to model the transfer of radionuclides through the environment. It concludes that equilibrium concentration ratios (CRs) are most commonly used to model such transfers, and that they currently offer the most comprehensive data coverage. The report also reviews the methods used to derive CRs, and describes a means of summarising statistical information from empirical data sets. Emphasis has been placed on using data from field studies, although some data from laboratory experiments have been included for some RAPs. There are, inevitably, many data gaps for each RAP, and other data have been used to help fill these gaps. CRs specific to each RAP were extracted from a larger database, structured in terms of generic wildlife groups. In cases where data were lacking, values from taxonomically-related organisms were used to derive suitable surrogate values. The full set of rules which have been applied for filling gaps in RAP-specific CRs is described. Statistical summaries of the data sets are provided, and CR values for 39 elements and 12 RAP combinations are given. The data coverage, reliance on derived values, and applicability of the CR approach for each of the RAPs is discussed. Finally, some consideration is given to approaches where RAPs and their life stages could be measured for the elements of interest under more rigorously controlled conditions to help fill the current data gaps.

Chronic exposure to pentavalent arsenic of larval leopard frogs (Rana pipiens): bioaccumulation and reduced swimming performance

Arsenic (As) is mainly released to the environment from anthropogenic sources, with inorganic pentavalent As (As [V]) predominant in surface water. In this study, Rana pipiens were exposed to As (V) in water at environmentally relevant concentrations (control, 10, 20, 150, 500, and 1,000 microg l(-1)) in a static-renewal system from post-hatch stage through metamorphosis for 113 days. There was no significant effect of As exposure on tadpole survival, growth, and percent metamorphosis. Maximum swimming speed was significantly slower in the As-treated groups compared with the control. During the period of tail resorption (Gosner stage 42-46), no significant differences in age at metamorphosis, survival, length of tail resorption period, snout-vent length of metamorphs, and sex ratio were found among treatments. Whole body As concentrations ranged from <0.6 to 5.31 mg kg(-1) dry mass, and were significantly higher in the 150, 500, and 1,000 microg l(-1) treatments than the control. Based on our data, larval tissue concentrations of As close to that reported in previous field studies were not associated with any significant effects except decreased tadpole swimming speed.

Derivation of transfer parameters for use within the ERICA Tool and the default concentration ratios for terrestrial biota

An ability to predict radionuclide activity concentrations in biota is a requirement of any method assessing the exposure of biota to ionising radiation. Within the ERICA Tool fresh weight whole-body activity concentrations in organisms are estimated using concentration ratios (the ratio of the activity concentration in the organism to the activity concentration in an environmental media). This paper describes the methodology used to derive the default terrestrial ecosystem concentration ratio database available within the ERICA Tool and provides details of the provenance of each value for terrestrial reference organisms. As the ERICA Tool considers 13 terrestrial reference organisms and the radioisotopes of 31 elements, a total of 403 concentration ratios were required for terrestrial reference organisms. Of these, 129 could be derived from literature review. The approaches taken for selecting the remaining values are described. These included, for example, assuming values for similar reference organisms and/or biogeochemically similar elements, and various simple modelling approaches.

Alterations in glutathione reductase, superoxide dismutase, and lipid peroxidation of tadpoles (Xenopus laevis) exposed to Bonny Light crude oil and its fractions

We determined the effects of sub-lethal levels of Bonny Light crude oil (WC) and its water soluble (WSF) and insoluble (WIF) fractions on malondialdehyde (MDA) and stress enzymes in tadpoles (Xenopus laevis) following two and 4 weeks exposure at different concentrations. We observed that the treatment of tadpoles with WC, WSF, or WIF decreased the weight of tadpoles, increased MDA levels, and increased superoxide dismutase (SOD) and glutathione reductase (GR) at lower concentrations of exposure and decreased the enzymes at higher doses of exposure. We found that the WC had a lesser negative effect on the parameters of tadpoles compared to the WSF. Longer exposure of tadpoles to WC, WSF, or WIF even at lower concentrations resulted in a negative effect on MDA, SOD, and GR activities The study shows that sub-lethal contaminations with WC, WSF, or WIF induces membrane lipid peroxidation and reduce the ability of tadpoles to produce SOD and GR which may have metabolic costs.

Effect of mono-ortho and di-ortho substituted polychlorinated biphenyl (PCB) congeners on leopard frog survival and sexual development

We tested the effect of mono-ortho and di-ortho PCB congeners on northern leopard frog (Rana pipiens) hatching success, survival and sexual development. Embryos and tadpoles were exposed to two levels (0.5 and 50 microg/l) of two PCBs. PCBs 101 and 70 were selected because they were present in amphibians collected in the Fox River-Green Bay ecosystem and they have the theoretical structural requirements to be able to bind to the estrogen receptor and mediate estrogenic responses. The exposure of leopard frog embryos and tadpoles to PCB 70 and 101 did not significantly affect hatchability, survival, deformities or growth. There were significant departures from the expected 50:50 sex ratio in tadpoles/froglets exposed to PCB 101 and PCB 70. In all the cases of significant departure, the bias was towards higher number of females. Decrease in the proportion of male gonads and increase in the proportion of intersex gonads were observed with increasing PCB tissue concentrations. The effects of PCB congeners on sexual differentiation occur at concentrations higher than observed in frogs in the Fox River/Green Bay ecosystem.

Delayed effects of environmentally relevant concentrations of 3,3',4,4'-tetrachlorobiphenyl (PCB-77) and non-polar sediment extracts detected in the prolonged-FETAX

In the prolonged-FETAX (prolonged-Frog Embryo Teratogenic Assay-Xenopus) tadpoles are allowed to develop until metamorphosis after an initial 4 day early life-stage exposure (FETAX). PCB 77 (3,4,3',4'-tetrachlorobiphenyl) and sediment extracts were used in the presented experiments. Concentrations of PCB 77 (0.03 nM=8.55 ng/L; 3 nM=855 ng/L; 300 nM=85.5 microg/L, 30,000 nM=8.55 mg/L) were derived on the basis of dioxin-like toxic equivalency concentrations known to be present in pore-water. The results were compared to those obtained with the standard FETAX. In the prolonged-FETAX the percentage of animals passing metamorphosis within 115 days was significantly decreased in the groups exposed to 300 or 30,000 nM PCB 77. Significantly increased percentages of tadpoles were halted in thyroid hormone dependent early metamorphic NF stages <or=55 (3 nM PCB 77) and metamorphic stages 56-60 tadpoles (300 nM PCB 77 and 30,000 nM PCB 77). Non-polar sediment extracts from two contaminated Dutch sites significantly decreased, and one significantly increased the percentage of animals that passed metamorphosis. These results were in accordance with earlier in vitro results in a thyroid hormone dependent assay and strongly suggest the presence of thyroid hormone disrupting compounds in the aquatic environment. In the classical FETAX neither PCB 77 nor non-polar sediment extracts induced any effects. The results of the present study indicate that the prolonged-FETAX is an important in vivo tool in addition to the in vitro T-screen to assess long-term effects of early life-stage exposure to environmentally relevant concentrations of (mixtures of) compounds and that affect thyroid hormone dependent physiology.

Lethal and sublethal effects of chronic cadmium exposure on northern leopard frog (Rana pipiens) tadpoles

Data on the chronic effects of cadmium on amphibians are lacking in spite of widespread anthropogenic contamination of terrestrial and aquatic systems. We exposed embryos and tadpoles of northern leopard frogs (Rana pipiens) to Cd (control, 0.25, 5.0, and 20.0 microg/L as CdCl2, nominal concentrations) in a static renewal system from embryonic stages to complete tail resorption. Survival of embryos (Gosner stage [GS] 17-25) was greater than 97% in all treatments. Tadpole survival was negatively correlated with dose and was significantly reduced in the 5.0 and 20.0 microg/L treatments compared with controls. Tadpole survival was greater than 80% through GS 42, forelimb emergence, for all other treatments. Tadpoles exposed to 0.25 and 5.0 microg/L exhibited increased growth by week 11; tadpoles exposed to 5.0 microg/L were significantly younger at forelimb emergence. Whole-tadpole body burdens of Cd were positively correlated with increasing Cd treatments. Cadmium was shown to alter growth and development in a native amphibian species at ecologically relevant concentrations. The existing chronic water quality criterion for Cd appears to be protective of amphibians. However, additional studies with other chemicals are needed to further explore the potential for adverse effects of contaminants on the complex life cycle of amphibians.