Fragmentation and depolymerization of microplastics in the earthworm gut: A potential for microplastic...

Area of Science:

• Environmental Science
• Ecotoxicology
• Soil Biology

Background:

• Microplastic accumulation in soils poses significant environmental risks.
• Understanding the fate of microplastics in terrestrial ecosystems is crucial.
• Earthworms are key soil ecosystem engineers with potential roles in organic matter decomposition.

Purpose of the Study:

• To investigate the potential of Lumbricus terrestris to reduce soil contamination by low-density polyethylene (LDPE), polylactic acid (PLA), and polybutylene adipate terephthalate (PBAT) microplastics.
• To examine the ingestion, fragmentation, and depolymerization of microplastics by earthworms.
• To assess the survival rates of earthworms exposed to microplastics.

Main Methods:

• Earthworms were exposed to microplastic-contaminated soil (1% microplastics) in a mesocosm system and pure microplastics in Petri dishes.
• Microplastic ingestion, size distribution changes in the gut, and earthworm survival were monitored.
• Molecular weight analysis was performed on microplastics recovered from earthworm guts and soil.

Main Results:

• Earthworms survived well in microplastic-contaminated soil but showed high mortality when exposed solely to microplastics.
• Microplastics were fragmented in the earthworm gizzard, with soil facilitating LDPE fragmentation.
• Substantial depolymerization of PLA and suspected depolymerization of PBAT occurred in the earthworm gut, unlike in soil alone.

Conclusions:

• Earthworm ingestion leads to microplastic fragmentation and, for certain polymers (PLA, PBAT), depolymerization within the gut.
• Lumbricus terrestris demonstrates a capacity for processing and potentially degrading microplastics.
• Further research is warranted to elucidate depolymerization mechanisms and assess the feasibility of earthworm-mediated microplastic bioremediation.