Short-term effect of poly lactic acid microplastics uptake by Eudrilus eugenia

The present study investigated the uptake of polylactic acid (PLA) microplastics, the most commonly used biodegradable plastic by Eudrilus eugeniae. It was done by observing their weight changes, biomass, and microplastics concentration after feeding them with a mixture of PLA and cow dung for 16 days at the ratio of 0%, 10%, 30%, 60%, and 80% w/w dry weight. The mortality rate of the earthworms for all the PLA concentrations during the 16 days of the feeding period was 0%. However, the microplastic significantly affected the earthworms' weight (P-value 0.00027), especially at 80% of PLA concentration. The earthworms had the lowest weight gain at 80%, followed by 60%, 30%, and 10% of PLA, respectively. The earthworms subjected to 80% and 10% of PLA had a similar pattern with the control. The PLA microplastics concentration factor (CF) in the vermicast was the highest at the 10% PLA than other treatments because Eudrilus eugeniae did not degrade the PLA. This study concludes that even though PLA is biopolymer-based, the earthworm cannot assimilate it. However, in the long run, there is a possibility of further degradation of the PLA MPs ejected in the vermicast due to the rich microbial environment provided by the earthworms and vermicast.