Potential Impacts of Climate Change on the Toxicity of Pesticides towards Earthworms.

This review examined one of the effects of climate change that has only recently received attention, i.e., climate change impacts on the distribution and toxicity of chemical contaminants in the environment. As ecosystem engineers, earthworms are potentially threatened by the increasing use of pesticides. Increases in temperature, precipitation regime changes, and related extreme climate events can potentially affect pesticide toxicity. This review of original research articles, reviews, and governmental and intergovernmental reports focused on the interactions between toxicants and environmental parameters. The latter included temperature, moisture, acidification, hypoxia, soil carbon cycle, and soil dynamics, as altered by climate change. Dynamic interactions between climate change and contaminants can be particularly problematic for organisms since organisms have an upper and lower physiological range, resulting in impacts on their acclimatization capacity. Climate change variables such as temperature and soil moisture also have an impact on acidification. An increase in temperature will impact precipitation which might impact soil pH. Also, an increase in precipitation can result in flooding which can reduce the population of earthworms by not giving juvenile earthworms enough time to develop into reproductive adults. As an independent stressor, hypoxia can affect soil organisms, alter bioavailability, and increase the toxicity of chemicals in some cases. Climate change variables, especially temperature and soil moisture, significantly affect the bioavailability of pesticides in the soil and the growth and reproduction of earthworm species.

Ecotoxicity of Mine Tailings: Unrehabilitated Versus Rehabilitated.

Earthworms are bioindicators of soil pollution. The ecotoxicity of tailings from selected gold mines in South Africa was investigated utilizing Eisenia andrei bioassays and biomarkers. Samples were obtained from unrehabilitated, rehabilitated and naturally vegetated sites. Biomass, neutral red retention time (NRRT), survival and reproduction were assessed using standardized protocols. Earthworm biomass, NRRT and reproductive success in rehabilitated tailings (comparable to naturally vegetated site) were significantly higher (p < 0.05) than in unrehabilitated tailings. In addition, significantly lower (p < 0.05) body tissue concentrations of As, Cd, Co, Cu and Ni contents were found in the rehabilitated tailings compared to the unrehabilitated. Further, significantly lower (p < 0.05) soil Mn and Zn concentrations were obtained in unrehabilitated tailings than the rehabilitated and naturally vegetated sites. Overall, reduced ecotoxicity effects were confirmed in rehabilitated compared to unrehabilitated tailings. This suggests that rehabilitation as a post-mining restorative strategy has strong positive influence on mine tailings.

Soil mesofauna as bioindicators to assess environmental disturbance at a platinum mine in South Africa.

South Africa is rich in mineral resources and is one of the leading raw material exporters in the world. Mining is essential for economic development, but also has detrimental environmental consequences in the form of chemical waste products which are being dumped as tailings material. The aim of this study was to establish whether mesofauna could be utilized to assess the influence of the tailings disposal facility on the surrounding soil environment. The sampled soil was chemically analyzed and the extracted mesofauna identified. High metal concentrations on the tailings dam (Cu, Cr and Ni), apparently had the greatest influence on the soil mesofauna. Only a few mite species were abundant at the two sites on the tailings dam, representing the prostigmatic-, cryptostigmatic- and the mesostigmatic-taxa. Metal pollution is evident in the sites on the tailings dam facility and the number of species generally increased towards the more natural environment.

The implications of copper fungicide usage in vineyards for earthworm activity and resulting sustainable soil quality.

To investigate the impact of copper-containing fungicides (copper oxychloride) on earthworms in South African vineyards, field inventories of earthworms in and between vine rows were carried out and compared to directly adjacent grassland. Also copper content, pH, organic matter content, and soil porosity were determined in these soils. This was combined with laboratory experiments to study the impact of vineyard soil characteristics on the burrowing and dispersal behavior of earthworms. Moreover, the direct toxic action of copper oxychloride on different endpoints of the earthworms (survival and growth) was studied. Copper oxychloride had a negative impact on these endpoints (decreased growth and survival related to increased copper body content) as well as on the behavioral aspect (decreased burrowing rate and avoidance of copper-containing soil). Moreover, there was an inverse relation between burrowing activity and soil bulk density that could also be related to the copper content. This may lead to a decrease in sustainable soil quality in vineyards.

The relationship between lysosomal biomarker and organismal responses in an acute toxicity test with Eisenia Fetida (Oligochaeta) exposed to the fungicide copper oxychloride.

The LC50 of copper oxychloride for Eisenia fetida was determined, and its effects on biomass change and lysosomal damage using neutral red retention times (NRRT) of coelomocytes were measured. The aim was to establish whether a lysosomal subcellular response, measured as NRRT, could be linked to the LC50 and biomass changes. Further, we attempted to establish the ecological relevance of the LC50 by comparing it to studies previously carried out on the effects of copper oxychloride on field earthworm populations. The experiment was conducted over a period of 28 days, during which the earthworms were exposed to different concentrations of copper oxychloride in artificial soil. The calculated LC50 was 883 microg g(-1) for copper oxychloride and 519 microg g(-1) for copper. Results indicated that changes in coelomocyte membrane stability manifested earlier than effects on biomass. Since the NRRT assay was very sensitive and generated an early response before changes in biomass or mortality could be measured, it may have predictive value and may contribute information during acute toxicity tests, which could be of greater ecological relevance than mortality data alone.

Linking lysosomal biomarker and population responses in a field population of Aporrectodea caliginosa (Oligochaeta) exposed to the fungicide copper oxychloride.

The effects of the fungicide copper oxychloride on a field population of the earthworm Aporrectodea caliginosa were investigated. Changes were monitored in earthworm numbers and biomass, copper concentrations in soil and earthworms, and neutral red retention times (NRRTs) of coelomocytes. The aim was to establish whether the cellular responses could be linked to changes at the population level. Results indicated that there was a significant (P<0.05) impact on worm density and biomass on the treated plots 6 months after spraying with the fungicide stopped. NRRTs of treated earthworms were significantly lower after one spraying when earthworms had elevated concentrations of copper in their body tissues. Six months after spraying stopped, copper levels in both soil and earthworm tissues declined significantly, but the earthworm numbers and biomass were still significantly lower in the treated plots. This indicated that the effects of the copper oxychloride exposure manifested at a much later stage at the population level, than on NRRT. We conclude that the decrease in NRRTs, which preceded the decrease in both earthworm biomass and numbers, may have predictive value as a biomarker of impending population changes.

Vermicomposting of industrially produced woodchips and sewage sludge utilizing Eisenia fetida.

Adult Eisenia fetida were used to vermicompost woodchips (WC) and sewage sludge (SS) that are produced as waste product by platinum mines. The aims of the study were to examine the growth and reproductive success of the worms over 84 days to determine long-term feasibility of large-scale implementation and monitor the bioconcentration of heavy metals and the effects of microorganisms inoculation to quantify possible environmental implications. Results revealed that there were no effects on growth (P>0.05), reproductive success decreased (P<0.05), and aluminum (Al), copper (Cu), and nickel (Ni) were bioconcentrated (P<0.05) in the treatment groups without an inoculate. Earthworms in the treatment group with the microorganism inoculate manifested no effects on growth or reproductive success and did not accumulate Al, Cu, and Ni. It is concluded that the only economically feasible way to bioconvert WC and SS to a potential ameliorant of platinum mine tailings would be with the addition of a microorganism inoculate.

The relation between lysosomal biomarker and population responses in a field population of Microchaetus sp. (oligochaeta) exposed to the fungicide copper oxychloride.

The ecological relevance of the neutral red retention assay as a biomarker in an indigenous earthworm population (Microchaetus sp.) exposed to the fungicide copper oxychloride was investigated. Changes in earthworm biomass and numbers were monitored and related to changes in neutral red retention times of coelomocytes as well as changes in copper concentrations in the soil and earthworm body tissues. Results indicated that Microchaetus sp. responded sensitively to the copper oxychloride by showing an initial decrease in biomass 2 months after spraying started. This was followed by a significant decrease in worm numbers after 3 months. The neutral red retention times of earthworm coelomocytes decreased significantly within the first month of treatment and correspond to a significant increase in soil copper concentrations, but not with an immediate increase in body burdens of copper. More than a year after spraying had stopped the worm biomass and numbers were still significantly lower in the treated plots compared with the control plots. Since the reduction in neutral red retention times could be attributed to the presence of copper oxychloride and preceded the decline in population density and biomass, we conclude that this biomarker has a useful role to play in environmental risk assessment and could provide a warning of impending ecological damage.

Effects of low levels of lead on growth and reproduction of the Asian earthworm Perionyx excavatus (Oligochaeta).

The effects of sublethal concentrations of lead nitrate on growth and reproduction of the Asian composting earthworm species Perionyx excavatus was studied experimentally by exposing worms in an organic substrate to lead nitrate-contaminated food over a period of 76 days. The results revealed that growth was affected negatively by the presence of lead while maturation rate and cocoon production was not affected. In agreement with other studies on Eisenia fetida, cocoon viability was affected negatively by lead, making this a sensitive toxicity endpoint. Lead accumulation was of the same order of magnitude as for other previously studied species.