Toxic effects of class II biodegradable plastics on Microcystis aeruginosa.

In this study, polylactic acid (PLA), polybutylene glycol terephthalate (PBAT) in biodegradable plastics (BMPs) and polyethylene (PE) in conventional microplastics (CMPs) were selected as test chemicals, and Microcystis aeruginosa was used as the test organism. By testing indicators such as algal cell density, chlorophyll a (Chl-a), superoxide dismutase (SOD), catalase (CAT), malondialdehyde (MDA), total intracellular soluble protein (TP) and reactive oxygen species (ROS), the effects of different dosages (50, 100, 150 and 200mg/L) and particle size (150, 250 and 500 µm) of PLA, PBAT and PE on the growth, oxidative stress and cell damage of Microcystis aeruginosa were investigated. The results showed that the growth and oxidative stress indexes of algal cells exhibited significant changes with exposure time under the single action of PLA/PBAT/PE. After 96h of exposure, compared with other treatment groups, the inhibition rate of PLA at a dosage of 100mg/L on Microcystis aeruginosa was the highest (16.31%), while the inhibition rate of PE at a particle size of 150 µm was the highest (15.97%). The exposure of PLA and PE significantly increased the contents of ROS, SOD, CAT and MDA in Microcystis aeruginosa, and their acute toxicity differences may be related to the roughness of the microplastic surfaces. PLA, as an aliphatic polyester, was more prone to hydrolysis in aquatic environments than PBAT, and the release potential of secondary microplastic fragments made it more severely acute toxic to algae. © 2024 Chinese Society for Environmental Sciences. All rights reserved.