Leg deformities of oribatid mites as an indicator of environmental pollution

Environmental exposure to metallic pollution impairs honey bee brain development and cognition

Laboratory studies show detrimental effects of metallic pollutants on invertebrate behaviour and cognition, even at low levels. Here we report a field study on Western honey bees exposed to metal and metalloid pollution through dusts, food and water at a historic mining site. We analysed more than 1000 bees from five apiaries along a gradient of contamination within 11 km of a former gold mine in Southern France. Bees collected close to the mine exhibited olfactory learning performances lower by 36% and heads smaller by 4%. Three-dimensional scans of bee brains showed that the olfactory centres of insects sampled close to the mine were also 4% smaller, indicating neurodevelopmental issues. Our study raises serious concerns about the health of honey bee populations in areas polluted with potentially harmful elements, particularly with arsenic, and illustrates how standard cognitive tests can be used for risk assessment.

Bioaccumulation of chemical elements at post-industrial freshwater sites varies predictably between habitats, elements and taxa: A power law approach

Elevated environmental levels of elements originating from anthropogenic activities threaten natural communities and public health, as these elements can persist and bioaccumulate in the environment. However, their environmental risks and bioaccumulation patterns are often habitat-, species- and element-specific. We studied the bioaccumulation patterns of 11 elements in seven freshwater taxa in post-mining habitats in the Czech Republic, ranging from less polluted mining ponds to highly polluted fly ash lagoons. We found nonlinear, power-law relationships between the environmental and tissue concentrations of the elements, which may explain differences in bioaccumulation factors (BAF) reported in the literature. Tissue concentrations were driven by the environmental concentrations in non-essential elements (Al, As, Co, Cr, Ni, Pb and V), but this dependence was limited in essential elements (Cu, Mn, Se and Zn). Tissue concentrations of most elements were also more closely related to substrate than to water concentrations. Bioaccumulation was habitat specific in eight elements: stronger in mining ponds for Al and Pb, and stronger in fly ash lagoons for As, Cu, Mn, Pb, Se, V and Zn, although the differences were often minor. Bioaccumulation of some elements further increased in mineral-rich localities. Proximity to substrate, rather than trophic level, drove increased bioaccumulation levels across taxa. This highlights the importance of substrate as a pollutant reservoir in standing freshwaters and suggests that benthic taxa, such as molluscs (e.g., Physella) and other macroinvertebrates (e.g., Nepa), constitute good bioindicators. Despite the higher environmental risks in fly ash lagoons than in mining ponds, the observed ability of freshwater biota to sustain pollution supports the conservation potential of post-industrial sites. The power law approach used here to quantify and disentangle the effects of various bioaccumulation drivers may be helpful in additional contexts, increasing our ability to predict the effects of other contaminants and environmental hazards on biota.

Low-level environmental metal pollution is associated with altered gut microbiota of a wild rodent, the bank vole (Myodes glareolus)

Mining and related industries are a major source of metal pollution. In contrast to the well-studied effects of exposure to metals on animal physiology and health, the impacts of environmental metal pollution on the gut microbiota of wild animals are virtually unknown. As the gut microbiota is a key component of host health, it is important to understand whether metal pollution can alter wild animal gut microbiota composition. Using a combination of 16S rRNA amplicon sequencing and quantification of metal levels in kidneys, we assessed whether multi-metal exposure (the sum of normalized levels of fifteen metals) was associated with changes in gut microbiota of wild bank voles (Myodes glareolus) from two locations in Finland. Exposure to increased metal load was associated with higher gut microbiota species diversity (α-diversity) and altered community composition (β-diversity), but not dispersion. Multi-metal exposure and increased levels of several metals (Cd, Hg, Pb and Se) were associated with differences in the abundance of microbial taxa, especially those within the families Clostridiales vadinBB60 group, Desulfovibrionaceae, Lachnospiraceae, Muribaculaceae and Ruminococcaceae. Our data indicate that even low-level metal pollution can affect the diversity of microbiota and be associated with deterministic differences in composition of host gut microbiota in wild animal populations. These findings highlight the need to study a broader range of metals and their cocktails that are more representative of the types of environmental exposure experienced by wild animals.

Ecotoxicological assessment after the world's largest tailing dam collapse (Fundão dam, Mariana, Brazil): effects on oribatid mites

Worldwide, environmental tragedies involving mining dam ruptures have become more frequent. As occurred a few years ago in Brazil (on 5 November 2015, in Minas Gerais state) the Fundão Dam rupture released 60 million m³ of tailings into terrestrial and aquatic ecosystems. Since then, little information on the ecotoxicity of these tailings has been disclosed. In the laboratory, the acute, chronic and bioaccumulation effects of increased Fundão tailing concentrations on oribatid mites (Scheloribates praeincisus) were assessed. Additionally, the bioaccumulation of 11 trace metals (Al, As, Cd, Cr, Cu, Fe, Hg, Mn, Ni, Pb and Zn) and the total density of oribatid mites found in the areas contaminated by the Fundão tailings were determined. The percentages of mite survival and reproductive inhibition were higher than 60% and 80%, respectively, in all contaminated areas with the highest concentration (100% mine tailings). Field studies showed an expressive reduction in the total density of oribatids per m^-2 (up to 54 times) in the contaminated areas compared with the reference area. Metal accumulations in the field were 5.4 and 3.2 higher (for Ni and Hg, respectively) and up to two times higher (for most metals) than those in the laboratory for 42 days. The mite responses to the Fundão tailings found in this study suggest long-term interference in their biological development. In this sense, we can conclude that the introduction of mine tailings onto soils tended to compromise the functionality of the mites in the ecosystem, which causes imbalances to cascade other organisms of the trophic web.

Leaves, berries and herbivorous larvae of bilberry Vaccinium myrtillus as sources of metals in food chains at a Cu-Ni smelter site

Ericaceous dwarf shrubs, such as bilberry, Vaccinium myrtillus, have an important role in nutrient cycling of boreal forests, but in metal polluted environments they also form a link between heavy metal pool of the soil, primary consumers and upper trophic levels. From the viewpoint of metal transfer in a food chain, we document metallic element (As, Ca, Cd, Co, Cu, Mn, Mo, Ni, Pb, Se, Zn) concentrations in leaves, berries and herbivorous larvae of V. myrtillus around a Finnish copper-nickel smelter and compare those with levels in relatively unpolluted reference sites, and with levels documented in soil and feces (a proxy of dietary levels) of an insectivorous bird, the pied flycatcher, Ficedula hypoleuca. Herbivorous larvae of the autumnal moth, Epirrita autumnata (Lepidoptera: Geometridae), grown experimentally on V. myrtillus, showed slower growth rate but not higher mortality in the polluted area. In general, metal levels in leaves, berries and larvae were higher in the polluted area and comparable to those reported at other smelter sites in Europe. The levels of the main toxic metals (As, Cd, Cu, Ni, Pb) followed the general pattern: soil > bird feces > leaves > larvae = berries, and levels in V. myrtillus, E. autumnata and F. hypoleuca reflected soil metal levels. The lowest levels were found in those matrices that are most important sources of food for birds and humans, i.e. leaf-eating larvae and berries, reducing a risk of toxic effects.

Morphology and the central nervous system of Eratigena atrica affected by a complex anomaly in the anterior part of the prosoma

Spider embryogenesis is affected by a range of environmental factors. Any sudden, drastic change in the environment may impair spider development, leading to various body deformities. In the present study, we analyze changes in the morphology and structure of the central nervous system of an Eratigena atrica larva, obtained in a teratological experiment in which embryos were exposed to alternating temperatures of 14 and 32 °C for the first 10 days. The studied larva had three pedipalps on the right side of the prosoma (polymely), two of which were fused along their entire length (total heterosymely). In addition, there was a short, club-shaped stump between the pedipalps. Histological analysis confirmed major changes in the structure of the subesophageal ganglion, i.e., the fusion of all three ganglia of pedipalps.

Long-term recovery of clutch size and egg shell quality of the pied flycatcher (Ficedula hypoleuca) in a metal polluted area

We explored if breeding parameters and egg shell quality of an insectivorous passerine, pied flycatcher Ficedula hypoleuca, have fully recovered after c.a. 99% decrease in dust emissions from a non-ferrous smelter in the course of the 23 year study period. Some potentially important population characteristics (density, phenology, age) and environmental variables (habitat, inter-specific competition) were taken into account in the analysis. We found marked increase in reproductive parameters (egg shell quality, clutch size, hatchability, and fledgling number) in the metal polluted area especially in 1990's when metal-rich dust emissions from the smelter were markedly reduced. Still clutch sizes and fledgling numbers remain below the levels of the reference area. There is currently very little evidence of direct toxic effects of metals in our study population but full recovery of breeding parameters may not be reached until the full recovery of food chains, which is likely to be a slow process.

Cd and Pb contents in soil, plants, and grasshoppers along a pollution gradient in Huludao City, Northeast China

Cd and Pb contents in soil, plants, and two grasshopper species (Locusta migratoria manilensis and Acrida chinensis) were examined to quantify the influence ranges of zinc smelting on heavy metal contamination. Samples were collected simultaneously from Huludao City, a chemical and nonferrous smelting base in Northeast China. Cd and Pb contamination in soil and plants were serious. Cd and Pb contents were 13.32 and 8.83 mg/kg in L. migratoria manilensis and 16.67 and 15.00 mg/kg in A. chinensis, respectively. Correlation analysis indicated the same metal source for Cd and Pb in soil, plants, and grasshoppers. Cd and Pb contents in soil, plants, and grasshoppers were all significantly related to distances far from the zinc smelter in good negative logarithm model. The fitting curves indicated that the influence radius of the smelter on heavy metal contamination was about 4,000 m for soil and plants and about 2,000 m for grasshoppers.