Effects of a mining‐altered environment on individual fitness of amphibians and reptiles

Abstract

Pollution can affect wildlife directly through toxicity and indirectly through changes in biotic and abiotic factors, however, how these mechanisms interact in affecting free‐ranging animals remains poorly understood. By examining effects on individual fitness proxies, we aimed to determine the mechanisms behind documented amphibian and reptile declines in barren landscapes where vegetation was nearly decimated due to atmospheric metal and sulfur deposition from smelting operations in Sudbury, Ontario, Canada. We examined individual characteristics of snakes (Thamnophis sirtalis, Storeria occipitomaculata) and frogs (Lithobates clamitans, L. pipiens, L. septentrionalis) in replicated barren and reference sites, including standard metabolic rates (in snakes), body condition (all species), female reproductive status (snakes), limb deformity (frogs), and fluctuating asymmetry (all species). Frogs in barren sites (except L. septentrionalis) were in poor body condition, and all but one case of limb deformities in frogs were found in barren sites. However, neither frogs nor snakes exhibited elevated frequency of fluctuating asymmetry in barren sites. Standard metabolic rates (SMR) were not elevated in either snake species, suggesting that metal toxicity does not present an energetic burden. Instead, female T. sirtalis from barren sites exhibited lower SMR and were in poor body condition, which is a predicted response to reduced food intake. By contrast, SMR and body condition of S. occipitomaculata were not different between barren and reference sites. While physiological responses differed between T. sirtalis and S. occipitomaculata, both species exhibited lower reproductive rates (proportion of pregnant females) in barren sites compared to reference sites. Thus, energy deficiency may explain reduced reproduction in T. sirtalis while reduced availability of suitable gestation microhabitat may be a limiting factor for S. occipitomaculata. Populations in smelting‐impacted habitats include individuals with potentially compromised fitness. The low values of our measured fitness proxies appear to have resulted from pollution‐induced changes in biotic and abiotic factors, in addition to (for frogs) or rather than (for snakes) from the direct toxicity. These results suggest that impact assessment based solely on toxicological data and species distributions can underestimate the full impacts of pollution, highlighting the need for integrated examination at multiple levels of biological organization.

The Bacterial Population of Neutral Mine Drainage Water of Elizabeth’s Shaft (Slovinky, Slovakia)

“…One of the most critical issues in mine environments is the natural oxidation (chemical and biological) of sulfide mineral tailings that are exposed to water, oxygen, and microorganisms. This oxidation is responsible for the generation of mine drainage that compromises the quality of soil, surface water, and sub-surface water bodies, hence affecting overall biodiversity [2][3][4][5].…”

“…These deposits are permanent source of toxic substances, especially heavy metals which contaminate all environmental compounds, mainly soil and water. Changes of water and soil quality affect also biodiversity of mining area [2][3][4][5]. The properties of drainage water depend on many factors, including mineralogical, geochemical properties, hydrogeological conditions, and the activity of lithoautotrophic microorganisms.…”

The relative performance of smooth snakes inhabiting open heathland and conifer plantations

“…All three life history traits (growth rate, reproductive output, and survivorship), usually used as a measure of habitat quality, are dependent to varying degrees on an animal's BC (Shine et al, 2001;Litzgus et al, 2008;Harrison et al, 2011;Gallego-Carmona et al, 2016;Sasaki et al, 2016) which in turn reflects the availability of energy, in terms of food/prey abundance and quality, within the habitat. Our study shows that the BC of heathland snakes remained relatively constant whilst that of plantation snakes, which was initially similar to that of heathland snakes, declined with increasing plantation age and was negatively correlated with increasing tree canopy cover.…”

“…In addition, most studies that have compared a species performance within different habitat types have done so in those habitats that are relatively stable (e.g. Morris, 1989;Mosser et al, 2009;Sasaki et al, 2016;Allen et al, 2017) whilst fewer have attempted to do so where at least one of the habitat types under investigation is transient (Welsh et al, 2008;Rotem et al 2013).…”

Are we accurately estimating the potential role of pollution in the decline of species at risk in Canada?

“…Nonetheless, sublethal effects of environmental pollutants on individuals can reduce their fitness, leading to population-level impacts (e.g., Kidd et al 2007;Incardona et al 2015). Notably, pollutants not only have direct toxic effects on organisms, but may also potentially cause harm through indirect pathways (e.g., trophic cascades; Kidd et al 2014;Sasaki et al 2016). Pollution can also compound the effects of other drivers of decline, weakening populations already affected by loss of habitat, overexploitation, or other threats (Brook et al 2008;Darling and Côté 2008).…”