Comprehensive Investigation of the Bioenergetic Responses and Toxicological Mechanisms of Diclofenac to Earthworm Eisenia fetida.

Diclofenac (DCF) is a widely used drug and has been frequently detected in treated municipal wastewaters. With the widespread promotion of wastewater reuse, DCF is inevitably introduced into agricultural ecosystems, but the knowledge of ecotoxicity on soil animals remains limited. This study evaluated the ecotoxicity of DCF on Eisenia fetida exposed to environmentally relevant concentrations. An integration of toxic end points, including growth, reproduction, and survival, were measured, and transcriptomic and metabolomic analyses were performed to explore the mechanism. The results showed that DCF exposure decreased earthworm growth and reproduction (even at 0.2 μg/L) and also led to lethality. Disruptions of energy supply in earthworms induced by oxidative stress mainly contributed the toxicity. Mechanism analyses further revealed that the DCF exposure inhibited glycolysis and tricarboxylic acid cycle rates and promoted protein catabolism for energy supply, which exacerbated the energy insufficiency and caused lethality. Collectively, it turned out that bioenergetic disorders were the primary causes for earthworms.