Mark Maboeta

Earthworm (Eisenia Fetida) bioassay to assess the possible effects of platinum tailings disposal facilities on the environment along a gradient

Platinum mines produce large amounts of inorganic tailings containing high levels of metals which are disposed of on tailings disposal facilities (TDFs) and there is no information available on their possible effects on the surrounding terrestrial environment. The aim of this study was to do an earthworm bioassay of soils along a gradient from a TDF over a period of 28 days in terms of growth, reproduction and metal accumulation. After 28 days the earthworms in the soil collected up to 1 km away from the TDF showed a significant (P < 0.05) decrease in bodyweight and in the soil 2−5 km away showed no effect. The earthworms in the soil collected 15 km away from the TDF showed a significant (P < 0.05) increase in bodyweight. The mean hatching success of cocoons was significantly (P < 0.05) higher in the soils further away from the TDF viz. 15 km > 3−5 km > 2−0 km. Cr, Cu, Ni and Zn concentrations in the soils collected in the soils on the platinum TDF (TDF − 15 km in the case of Zn) were higher, while Cd, Co and Pb were lower when compared to screening benchmarks proposed by the U.S. Dept. of Energy. The presence of these metals in a mixture, however, makes it extremely difficult to assess their effects. All of the metals had low bioconcentration factors (BCFs) viz. < 0.01 (CR, Ni and Pb), 0.01 (Co), 0.33−0.5 (Cd), 0.01−0.08 (Cu) and 0.18−0.29 (Zn). It can be concluded that platinum mining, with TDFs as source of contamination, has negative effects on the environment but further studies are needed to assess the exact extent of these effects.

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.

Heavy metal tolerance traits of filamentous fungi isolated from gold and gemstone mining sites

Increased environmental pollution has necessitated the need for eco-friendly clean-up strategies. Filamentous fungal species from gold and gemstone mine site soils were isolated, identified and assessed for their tolerance to varied heavy metal concentrations of cadmium (Cd), copper (Cu), lead (Pb), arsenic (As) and iron (Fe). The identities of the fungal strains were determined based on the internal transcribed spacer 1 and 2 (ITS 1 and ITS 2) regions. Mycelia growth of the fungal strains were subjected to a range of (0–100 Cd), (0–1000 Cu), (0–400 Pb), (0–500 As) and (0–800 Fe) concentrations (mgkg−1) incorporated into malt extract agar (MEA) in triplicates. Fungal radial growths were recorded every three days over a 13-days’ incubation period. Fungal strains were identified as Fomitopsis meliae, Trichoderma ghanense and Rhizopus microsporus. All test fungal exhibited tolerance to Cu, Pb, and Fe at all test concentrations (400–1000 mgkg−1), not differing significantly (p > 0.05) from the controls and with tolerance index >1. T. ghanense and R. microsporus demonstrated exceptional capacity for Cd and As concentrations, while showing no significant (p > 0.05) difference compared to the controls and with a tolerance index >1 at 25 mgkg−1 Cd and 125 mgkg−1 As. Remarkably, these fungal strains showed tolerance to metal concentrations exceeding globally permissible limits for contaminated soils. It is envisaged that this metal tolerance trait exhibited by these fungal strains may indicate their potentials as effective agents for bioremediative clean-up of heavy metal polluted environments.

Effects of Cry1Ab transgenic maize on lifecycle and biomarker responses of the earthworm, Eisenia andrei.

A 28-day study was conducted to determine the effects of the Bacillus thuringiensis Cry1Ab toxin on the earthworm Eisenia andrei. Previously, investigations have been limited to life-cycle level effects of this protein on earthworms, and mostly on E. fetida. In this study several endpoints were compared which included biomass changes, cocoon production, hatching success, a cellular metal-stress biomarker (Neutral Red Retention Time; NRRT) and potential genotoxic effects in terms of Randomly Amplified Polymorphic DNA sequences (RAPDs). NRRT results indicated no differences between treatments (p > 0.36), and NRRT remained the same for both treatments at different times during the experiment (p = 0.18). Likewise, no significant differences were found for cocoon production (p = 0.32) or hatching success (p = 0.29). Conversely, biomass data indicated a significant difference between the control treatment and the Bt treatment from the second week onwards (p < 0.001), with the Bt treatment losing significantly more weight than the isoline treatment. Possible confounding factors were identified that might have affected the differences in weight loss between groups. From the RAPD profiles no conclusive data were obtained that could link observed genetic variation to exposure of E. andrei to Cry1Ab proteins produced by Bt maize.

Heavy metal tolerance potential of Aspergillus strains isolated from mining sites

ABSTRACT Increased heavy metal pollution generated through anthropogenic activities into the environment has necessitated the need for eco-friendly remediation strategies such as mycoremediation. With a view to prospecting for fungi with heavy metal remediation potentials, the tolerance of five Aspergillus species isolated from soils of three active gold and gemstone mining sites in southwestern Nigeria to varied heavy metal concentrations was investigated. Isolated Aspergillus strains were identified based on the internal transcribed spacer 1 and 2 (ITS 1 and ITS 2) regions. Growth of Aspergillus strains were challenged with a range of varied concentrations of heavy metals: cadmium (Cd) (0–100), copper (Cu) (0–1000), lead (Pb) (0–400), arsenic (As) (0–500), and iron (Fe) (0–800) concentrations (ppm) incorporated into Malt Extract Agar (MEA) in triplicates. Mycelial radial growths were recorded at intervals of 3 days during a 13-day incubation period. Aspergillus strains were identified as A. tubingensis, A. fumigatus, A. terreus, A. nidulans, and A. nomius. A. tubingensis tolerated Cd, Cu, Pb, As, and Fe at all test concentrations (100–1000 ppm), showing no significant (p > .05) difference compared with the control. Similarly, A. nomius tolerated all concentrations of Cu, Pb, As, and Fe and only 50 ppm Cd concentrations. A. nidulans, A. terreus, and A. fumigatus, on the other hand, tolerated all concentrations of Cu, Pb, and Fe with no statistical significance (p > .05) difference from the controls. Overall, the Aspergillus species showed tolerance to heavy metal concentrations above permissible limits for contaminated soils globally. These heavy metal tolerance traits exhibited by the Aspergillus isolates may suggest that they are potential candidates for bioremediation of heavy metal–polluted environments.

Molecular assessment of commercial and laboratory stocks of Eisenia spp. (Oligochaeta: Lumbricidae) from South Africa

ABSTRACT DNA barcoding was used to investigate laboratory and commercial stocks of Eisenia species from four provinces of South Africa. The COI gene was partially amplified and sequenced in selected earthworms from eight local populations (focal groups) and two European laboratory stocks (non-focal groups). Only nine COI haplotypes were identified from the 224 sequences generated. One of these haplotypes was found to belong to the megascolecid Perionyx excavatus. The remaining eight haplotypes belonged to the genus Eisenia, although only a single E. fetida haplotype, represented by six specimens, was found in one of the European populations. The other seven haplotypes, all occurring in South Africa, were E. andrei. One of the commercial stocks from South Africa and a laboratory culture from Europe were mixtures of E. andrei-P. excavatus and E. andrei-E. fetida, respectively. Previous allozyme studies have helped to suggest that some of the populations included in this study may be suffering from inbreeding depression, which could result in adverse consequences for both the vermiculture industry and ecotoxicological research in South Africa.

Inadequate Taxonomy and Highly Divergent COI Haplotypes in Laboratory and Field Populations of Earthworms used in Ecotoxicology. A Case Study

DNA barcoding was used to investigate the phylogenetic delimitations of Eisenia sp. populations used in ecotoxicological research in South Africa. A total of three focal groups (used in published works) and two non-focal groups were assessed. These focal groups, including two laboratory cultures and one field population, have been referred to as Eisenia fetida in the literature. A previous molecular study had already helped to establish that one of the two laboratory groups was a population of E. fetidas sister species E. andrei. In the present contribution, analyses of the COI gene revealed that the taxonomy of the remaining laboratory and field populations had also been incorrectly assigned since all the generated sequences grouped unequivocally with published sequences of E. andrei. Very high sequence divergence (>25% K2P) found within E. andrei could signal the occurrence of hitherto undescribed cryptic species. These findings are discussed with an emphasis on the possible consequences of using poorly identified earthworms or specimens with high molecular divergence in ecotoxicological bioassays. It is not clear whether unbeknownst to the researchers, the use of cryptic species in bioassays could jeopardise the quality of ecotoxicological investigations. Early evidence suggests that cryptic oligochaete species may respond differently to metal toxicity. The need for comparative ecotoxicological studies between E. andrei and E. fetida is also evidenced, especially in the light of recent numerous reports of cryptic oligochaete species. Ecotoxicologists are consequently encouraged, whenever possible, to make use of available genomic technologies to screen their laboratory stocks and available field populations for any molecular distinctiveness.

The Enchytraeid Reproduction Test (ERT): A Potentially Quick and Affordable Tool for the Assessment of Metal Contaminated Soils in Emerging Economies

The enchytraeid reproduction test (ERT) was used to assess the ecotoxicity of selected mine tailings and agricultural soils from South Africa. The mine tailings had higher cumulative metal concentrations than agricultural soils. The most contaminated mine tailings significantly reduced the survival of the oligochaete Enchytraeus doerjesi whose reproduction was suppressed in all mine waste substrates. Because it reliably singled out the most contaminated substrate and was found easy to perform, we suggest that the ERT could be a quick and affordable tool for assigning intervention values for soil remediation in emerging economies such as South Africa.

Spatio-seasonal dynamics of bacteria and metal composition of a platinum mine tailings dam, Rustenburg, South Africa

Seasonal variations and proximity to polluted sites, among other factors, play a vital role in soil composition. The impact of spatio-seasonal changes on bacterial and heavy metal content on and around the platinum mine tailings dam, Rustenburg, South Africa, was assessed. Tailings and topsoils collected during summer and winter were examined for bacterial abundance, physicochemical parameters and metal contents using standard methods. Data were analysed using ANOVA, correlation and cluster analyses. Bacteria counts were 2.5 × 105 to 1.0 × 106 and 3.5 × 105 to 7.8 × 105 CFU g−1 in summer and winter, respectively. Molecular identification revealed the presence of the bacterial species Paenibacillus lautus and Stenotrophomonas maltophilia. Significant (p < 0.05) differences were obtained between chromium (Cr), copper (Cu) and nickel (Ni) concentrations in both seasons but not with bacterial counts. Although higher bacterial abundance was observed on sites 1 and 2 in both seasons. Relative abundance of Ni > Cu > Cr was observed with significantly (p < 0.05) higher concentrations in winter. Pearsons correlation (p < 0.05) and cluster (r = 0.60, p < 0.05) analyses confirmed strong positive correlations between bacteria and Cr, Cu and Ni concentrations. The high bacterial presence on sites in proximity to the dam may indicate metal tolerance of these species.

Assessing the ecotoxicity of gold mine tailings utilizing earthworm and microbial assays

Problems associated with mining are the disposal of wastes on tailing disposal facilities (TDFs). The aim of this study was to determine the ecotoxicity of gold mine tailings by using earthworm bioassays, earthworm biomarkers and enzymatic analyses. End points included changes in biomass, reproduction, lysosomal membrane stability, tissue metal concentrations, and selected enzymatic activities. Results indicated high concentrations of Ni in the material as well as bioaccumulation of lead and arsenic in the earthworm body tissue after exposure. Enzymatic activity was higher in revegetated tailings than in unrehabilitated tailings. It was concluded that TDF and surrounding areas have an acidic pH which affects earthworms and metal bioavailability. Soil enzymatic activities were a sensitive indicator of metal pollution in mining areas. Growth, reproduction and lysosomal membrane stability of earthworms have also been shown to be sensitive end points to assess the ecotoxic effects of gold TDF.