Suitable reservoirs and monitoring methods are needed to manage scarce water supplies in dry countries. We assessed here the impact on aquatic macroinvertebrates of the only dam on the Eerste River, which runs through the heart of a biodiversity hotspot, the Cape Floristic Region, South Africa. The dam and associated activities, were the only forms of disturbance in this otherwise pristine area. We sampled over 20,000 macroinvertebrate individuals and illustrated some categorical effects of the impoundment and its effects on macroinvertebrate assemblages. Macroinvertebrate species diversity below the dam was only half of that in the pristine catchment area above the dam. Furthermore, Ephemeroptera, Plecoptera and Trichoptera diversity and abundance dropped to almost zero as a result of the impoundment. In contrast, the abundance of the Diptera family Chironomidae increased substantially below the dam. These changes in macroinvertebrate diversity mirrored those recorded in biologically less diverse areas, but are of major concern in this biodiversity hotspot with its rich endemic fauna. We conclude that such an impoundment, while important for human welfare, results in a high price being paid in terms of loss of local biodiversity.

Globally, Fusarium root rot, which is caused by Fusarium graminearum, reduces wheat (Triticum aestivum L.) yield and quality up to 20%. Colonization of roots by F. graminearum has been recognized, but controlling Fusarium root rot using worm extracts (mucus, vermicompost tea, and vermiwash) has received little attention. We report the antagonistic properties of redworm (Eisenia fetida) extracts against F. graminearum and their effects on wheat seedling growth. Mycelial growth inhibition against the fungus was conducted in quintuplicate using the extracts in vitro. The extracts significantly inhibited mycelial growth of the fungus under in vitro conditions, and there was significant interaction between the infections and extracts for all the parameters measured (root and shoot lengths, root biomass, and disease index). Redworm mucus and 14‐d vermiwash produced moderately (26%) to relatively less (16%) antifungal activity, respectively. Vermiwash and augmented vermicompost tea were able to inhibit Fusarium root rot and improve (>58%) the growth of the inoculated seedlings under laboratory conditions. Vermiwash also acted as nutritional supplement, enhancing plant growth. The extracts suppressed F. graminearum and could serve as a potential bio‐fungicide in the integrated management of Fusarium root rot in wheat. Longer term experiments under field conditions are needed to validate the findings from the current study. Core Ideas The redworm extracts (vermiwash and augmented vermicompost tea) were able to inhibit Fusarium root rot (>58%) of the inoculated seedlings. Likewise redworm extracts acted as nutritional supplement, enhancing plant growth. Redworm extract suppressed F. graminearum and could serve as a potential bio‐fungicide in integrated management of Fusarium root rot in wheat.

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The present study investigated the use of biochar for the alleviation of the toxic effects of a nanosilver colloidal dispersion and a chloronicotinyl insecticide. The survival and reproduction of the potworm Enchytraeus albidus were assessed after exposure to imidacloprid and silver nanoparticles (AgNPs). E. albidus was exposed to 0, 25, 50, 100, 200, and 400 mg imidacloprid/kg and 0, 5, 25, 125, and 625 mg Ag/kg for 21 days in 10% biochar amended and non-biochar amended OECD artificial soil. In both exposure substrates, the effects of imidacloprid on survival were significant in the two highest treatments (p < 0.01). No biochar effect was observed as survival was statistically similar in both soils after exposure to imidacloprid. In the case of AgNPs, significant mortality was only observed in the highest AgNP treatments in both the amended and non-amended soils (p < 0.05). Nevertheless, statistically greater survival occurred in the biochar-amended treatment (p < 0.05). Reproduction results showed a more pronounced biochar effect with an EC = 22.27 mg imidacloprid/kg in the non-amended soil and a higher EC = 46.23 mg imidacloprid/kg in the biochar-amended soil. This indicated a 2-fold decrease in imidacloprid toxicity due to biochar amendment. A similar observation was made in the case of AgNPs where a reproduction EC = 166.70 mg Ag/kg soil in the non-amended soil increased to an EC > 625 mg Ag/kg soil (the highest AgNP treatment) in the amended soil. This indicated at least a 3.7-fold decrease in AgNPs toxicity due to biochar amendment. Although more studies may be needed to optimize the easing effects of biochar on the toxicity of these chemicals, the present results show that biochar could be useful for the alleviation of the toxic effects of imidacloprid and silver nanoparticles in the soil.

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