Chapter 12 - Exposure to emerging contaminants: ecotoxicological effects on earthworms and the potential of gut-associated microorganisms in bioremediation

Abstract

Tremendous population growth and an increase in industrial, agricultural, and healthcare products have resulted in an uncontrollable rise in the emission of new contaminants. These emerging contaminants (ECs) are present in the environment at low concentrations, but they have the potential to cause significant environmental harm. Earthworms, with feeding habits, are one of the terrestrial organisms that are continuously exposed to ECs in the soil. Due to their high sensitivity and multiple ecologic roles, they have been utilized as both a risk assessment tool and a bioremediation agent for numerous organic and inorganic contaminants. Nonetheless, it is still unknown whether the responses of earthworms to ECs during both functions are directly related to their gut microbiome. Being nutrient-rich, the earthworm gut is a well-organized microecosystem that promotes the colonization of microorganisms that have been shown to enhance the degradation and detoxification of certain ECs. In addition to investigating the role of gut microbial isolates, high-throughput sequencing approaches were used to assess the diversity of functional microorganisms in the earthworm intestine, which are selectively activated for improved host adaptation to a stressed, contaminated environment. Consequently, this chapter describes the toxicologic effects of ECs present in the soil on earthworms, the direct effects of ECs on the microbial diversity of earthworm gut, and the microbial genera associated with earthworm's intestine implicated in the bioremediation of several ECs. The final section will identify knowledge gaps that require further study to increase the use of earthworms as an ecotoxicologic risk assessment tool for ECs and the contribution of their gut microbiota to ensuring host health and the elimination of ECs.