Heavy metal effects on multitrophic level microbial communities and insights for ecological restoration of an abandoned electroplating factory site

The response of soil microbes to heavy metal pollution provides a metric to evaluate the soil health and ecological risks associated with heavy metal contamination. However, a multitrophic level perspective of how soil microbial communities and their functions respond to long-term exposure of multiple heavy metals remains unclear. Herein, we examined variations in soil microbial (including protists and bacteria) diversity, functional guilds and interactions along a pronounced metal pollution gradient in a field surrounding an abandoned electroplating factory. Given the stressful soil environment resulting from extremely high heavy metal concen-trations and low nutrients, beta diversity of protist increased, but that of bacteria decreased, at high versus low pollution sites. Additionally, the bacteria community showed low functional diversity and redundancy at the highly polluted sites. We further identified indicative genus and generalists in response to heavy metal pollution. Predatory protists in Cercozoa were the most sensitive protist taxa with respect to heavy metal pollution, whereas photosynthetic protists showed a tolerance for metal pollution and nutrient deficiency. The complexity of ecological networks increased, but the communication among the modules disappeared with increasing metal pollution levels. Subnetworks of tolerant bacteria displaying functional versatility (Blastococcus, Agromyces and Opitutus) and photosynthetic protists (microalgae) became more complex with increasing metal pollution levels, indicating their potential for use in bioremediation and restoration of abandoned industrial sites contaminated by heavy metals.

Automated summary

The response of soil microbes to heavy metal pollution is important in assessing soil health and ecological risks associated with heavy metal contamination. In this study, the effects of long-term exposure to multiple heavy metals on soil microbial communities were examined. It was found that protist diversity increased while bacterial diversity decreased at high pollution sites compared to low pollution sites. The bacteria community also showed low functional diversity and redundancy at highly polluted sites. Predatory protists in Cercozoa were found to be the most sensitive to heavy metal pollution, while photosynthetic protists showed tolerance. This study highlights the potential of certain bacteria and photosynthetic protists for bioremediation and restoration of heavily contaminated industrial sites.