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Here, we examine the effects of adjacent land use in a managed forest on pond-breeding amphibian species richness and community composition at 34 New Brunswick, Canada, ponds. Amphibian species richness was negatively correlated with the proportion of roads, precommercial thinning, and hardwood forest and positively correlated with the proportion of wetlands in adjacent lands. These land-use effects peak at 180 m from the ponds. Road density was negatively correlated with Lithobates catesbeiana and Lithobates septentrionalis presence. Precommercial thinning was negatively correlated with Ambystoma spp. presence and positively correlated with Anaxyrus americanus presence. Wetlands were positively correlated with L. septentrionalis and Notopthalamus viridescens presence. Correlations were also found between water table height and A. americanus, Lithobates palustris, and Ambystoma spp. presence. In addition, L. catesbeiana and N. viridescens presence-absence was positively correlated with the proportion of mature and overmature forest on the landscape (at scales of 500 and 1000 m, respectively). Lastly, the proportion of regenerating and sapling forest on the landscape was negatively correlated with L. palustris presence-absence but, by contrast, was positively correlated with A. americanus. These results suggest that the effects of adjacent land use may significantly impact amphibian populations in managed eastern Canadian forests. Nous avons examine, en regard de l'utilisation du territoire adjacent, la richesse specifique et la composition des communautes d'amphibiens de 34 etangs situes en foret amenagee au Nouveau-Brunswick, au Canada. La richesse specifique en amphibiens etait negativement correlee a la proportion de chemins, de peuplements traites par eclaircie precommer-ciale et de foret feuillue et positivement correlee a la proportion de milieux humides dans les territoires adjacents. Ces effets du contexte paysagers culminaient a 180 m des etangs. La densite des chemins etait negativement correlee a la presence de Lithobates catesbeiana et Lithobates septentrionalis. L'eclaircie precommerciale etait negativement correlee a la presence d'Ambystoma spp. et positivement correlee a la presence d'Anaxyrus americanus. Les milieux humides etaient positivement correles a la presence de L. septentrionalis et Notopthalamus viridescens. Des correlations ont aussi ete trouvees entre la hauteur de la nappe phreatique et la presence d'A. americanus, Lithobates palustris et Ambystoma spp. De plus, la presence-absence de L. catesbeiana et N. viridescens etait positivement correlee a la proportion de foret mature et surannee dans le paysage (aux echelles respectives de 500 et 1000 m). Finalement, la proportion de foret en regeneration et au stade gaulis dans le paysage etait negativement correlee a la presence-absence de L. palustris mais, a l'inverse, l'etait positivement avec A. americanus. Ces resultats indiquent que l'utilisation du territoire adjacent peut avoir des effets significatifs sur les populations d'amphibiens dans les forets amenagees de l'est du Canada. [Traduit par la Redaction], Introduction Forestry practices alter natural landscapes and may negatively affect wildlife populations and communities, especially if forests are not properly managed (Freedman et al. 1994; Noss 1999). In particular, amphibian [...]

Author(s): Jeff. E. Houlahan (corresponding author) [1]; C. Scott Findlay [1, 2]; Benedikt R. Schmidt [3]; Andrea H. Meyer [4]; Sergius L. Kuzmin Although there is growing concern that amphibian [...]

Kejimkujik National Park and National Historic Site, Nova Scotia, Canada, is considered a biological mercury (Hg) hotspot because the tissues of yellow perch ( Perca flavescens) and common loons ( Gavia immer) inhabiting the lakes frequently exceed so-called safe levels of Hg. In the present study, the relationships between Hg and overall health of males and females of 3 forage fish species (brown bullhead Ameirus nebulosus, banded killifish Fundulus diaphanus, and golden shiner Notemigonus crysoleucas; n = 6-18/sex/lake) in 6 lakes at the park were assessed using condition factor, liversomatic index (LSI), and macrophage aggregates (MAs; indicators of tissue damage). Mean muscle total Hg (THg) concentrations of brown bullhead, banded killifish, and golden shiner across lakes were 0.32 μg/g, 0.27 μg/g, and 0.34 μg/g, respectively. Condition was negatively related to muscle THg in golden shiner and banded killifish, LSI was not related to THg in any species, and all species showed evidence of increasing MA prevalence (counts and area) with increasing THg concentrations. The MAs were most prevalent in spleen tissues of golden shiner, with mean percentage cover ranging from 0.36% to 5.59% across lakes. In addition, the area of MAs appeared to be better predicted by THg concentration than was the number of MAs in the same tissue. These findings suggest that Hg is affecting the health of wild fishes in Kejimkujik National Park and National Historic Site and that other populations with similar or higher concentrations of this metal may also be at risk. Environ Toxicol Chem 2017;36:976-987. © 2016 SETAC [ABSTRACT FROM AUTHOR]

Many environments are undergoing rapid environmental change and there is a need to understand the mechanisms by which species can persist in altered environments. Model systems, such as amphibian metamorphosis, which can be generalized across many types of environmental change and across many species, are a powerful tool for understanding mechanisms that facilitate persistence in altered and disturbed environments. Amphibian larvae respond to environmental change by varying age at metamorphosis, or size at metamorphosis. Differential selection pressures on age or size at metamorphosis may result in a differential response among taxa to environmental change. Using a meta-analysis, we investigated whether age at metamorphosis, size at metamorphosis, and larval growth rate vary within and among taxonomic families of amphibians in experiments that modified the environmental temperature, density of individuals, food, hydroperiod and the presence of predators. For all environmental factors except predators, the direction of the response was consistent across most of the studied taxa. However, there was considerable variation in effect size both within and among families. Results demonstrate that amphibian metamorphosis is a valuable model system for studying the effects of environmental change. Yet, we stress the need for caution in making generalizations about how individuals respond to environmental factors that have an indirect effect on physiology and require the perception of an environmental cue, such as the presence of predators. [ABSTRACT FROM AUTHOR]

Laboratory and mesocosm experiments have demonstrated that some glyphosate-based herbicides can have negative effects on benthic invertebrate species. Although these herbicides are among the most widely used in agriculture, there have been few multiple-stressor, natural system-based investigations of the impacts of glyphosate-based herbicides in combination with fertilizers on the emergence patterns of chironomids from wetlands. Using a replicated, split-wetland experiment, the authors examined the effects of 2 nominal concentrations (2.88 mg acid equivalents/L and 0.21 mg acid equivalents/L) of the glyphosate herbicide Roundup WeatherMax, alone or in combination with nutrient additions, on the emergence of Chironomidae (Diptera) before and after herbicide-induced damage to macrophytes. There were no direct effects of treatment on the structure of the Chironomidae community or on the overall emergence rates. However, after macrophyte cover declined as a result of herbicide application, there were statistically significant increases in emergence in all but the highest herbicide treatment, which had also received no nutrients. There was a negative relationship between chironomid abundance and macrophyte cover on the treated sides of wetlands. Fertilizer application did not appear to compound the effects of the herbicide treatments. Although direct toxicity of Roundup WeatherMax was not apparent, the authors observed longer-term impacts, suggesting that the indirect effects of this herbicide deserve more consideration when assessing the ecological risk of using herbicides in proximity to wetlands. Environ Toxicol Chem 2014; 33:2076-2085. © 2014 SETAC [ABSTRACT FROM AUTHOR]

Herbicides are commonly used in agriculture and silviculture to reduce interspecific competition among plants and thereby enhance crop growth, quality, and volume. Internationally, glyphosate-based herbicides are the most widely used herbicides in both of these sectors. Laboratory and mesocosm studies have demonstrated that some formulations are toxic to amphibian larvae below concentrations that approximate predicted maximal or 'worst-case' exposure scenarios. However, field studies have not found evidence of toxicity at these concentrations. The authors conducted a replicated field experiment involving 10 naturalized wetlands split in half with an impermeable plastic barrier to assess the direct toxicity of a glyphosate formulation commonly used in silviculture (VisionMAX™). The herbicide formulation was applied directly to the surface of one side of each wetland at one of two target aqueous exposure rates (high = 2,880, low = 550 µg acid equivalents [a.e.]/L), and the other side was left as an untreated control. The survival and growth of green frog larvae ( Lithobates clamitans) were assessed for two years following herbicide treatment. The herbicide did not have a negative impact on survival or growth of L. clamitans larvae at either treatment level. In fact, mean larval abundance was typically greater in the treated sides than in control sides within the year of herbicide application. These results indicate that typical silviculture use of VisionMAX poses negligible risk to larval amphibians, likely because the combined effects of sorption and degradation in natural wetlands limit the exposure magnitude and duration. Environ. Toxicol. Chem. 2012; 31: 2375-2383. © 2012 SETAC [ABSTRACT FROM AUTHOR]

Null hypothesis significance testing has been under attack in recent years, partly owing to the arbitrary nature of setting a (the decision-making threshold and probability of Type I error) at a constant value, usually 0.05. If the goal of null hypothesis testing is to present conclusions in which we have the highest possible confidence, then the only logical decision-making threshold is the value that minimizes the probability (or occasionally, cost) of making errors. Setting α to minimize the combination of Type I and Type II error at a critical effect size can easily be accomplished for traditional statistical tests by calculating the α associated with the minimum average of α and β at the critical effect size. This technique also has the flexibility to incorporate prior probabilities of null and alternate hypotheses and/or relative costs of Type I and Type II errors, if known. Using an optimal α results in stronger scientific inferences because it estimates and minimizes both Type I errors and relevant Type II errors for a test. It also results in greater transparency concerning assumptions about relevant effect size(s) and the relative costs of Type I and II errors. By contrast, the use of α = 0.05 results in arbitrary decisions about what effect sizes will likely be considered significant, if real, and results in arbitrary amounts of Type II error for meaningful potential effect sizes. We cannot identify a rationale for continuing to arbitrarily use α = 0.05 for null hypothesis significance tests in any field, when it is possible to determine an optimal α. [ABSTRACT FROM AUTHOR]

The article discusses hypothsesis testing and minimization of environmental management decisions by optimization of statistical thresholds. It informs that environmental monitoring and research requires setting of appropriate alpha level. It also discusses the method to determine critical effect size for designing enviromental monitoring programs.

Analyzes a study which examined the means of trends for global amphibian population declines during the 1950s and 1960s. Application of the least-squares mean to estimate the annual mean global decline in amphibian population; Factors that contributed to amphibian population declines.