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Biodegradable and conventional microplastics posed similar toxicity to marine algae Chlorella vulgaris
Summary
Researchers compared the toxicity of biodegradable microplastics made from polylactic acid and polybutylene succinate with conventional microplastics made from polyethylene and polyamide on marine algae. They found that both types inhibited algal growth and photosynthesis to a similar degree, causing comparable oxidative stress and cell membrane damage. The study challenges the assumption that biodegradable plastics are inherently safer for marine ecosystems than conventional plastics.
It has been demonstrated that some conventional microplastics (CMPs) have toxicities to organisms, however, whether biodegradable microplastics (BMPs) have similar potential risks to marine ecosystems remains to be elucidated. Therefore, this study aimed to investigate i) the effects of CMPs (i. e., micro-sized polyethylene (mPE) and polyamide (mPA)) on marine algae Chlorella vulgaris; and ii) the potential effects of BMPs (i.e., micro-sized polylactic acid (mPLA) and polybutylene succinate (mPBS)) on C. vulgaris. The results showed that either CMPs or BMPs inhibited the growth of microalgae compared with the control. The maximum inhibition ratio of the four types of MPs on C. vulgaris were 47.24% (mPE, 1 000 mg/L), 40.36% (mPA, 100 mg/L), 47.95% (mPLA, 100 mg/L) and 34.25% (mPBS, 100 mg/L), respectively. Among them, mPLA showed the strongest inhibitory effect on the growth of C. vulgaris. Interestingly, the MPs can stimulate the contents of pigments (e.g., chlorophyll a, chlorophyll b, and carotenoid), which may be acted as cellular defense to the stress induced by MPs. The results also showed that MPs stimulated the production of EPS. Under the investigated condition, the strongest inhibition on C. vulgaris was induced by mPLA, and followed by mPE, mPA, and mPBS. It was found that the factors such as the physicochemical properties of MPs (e.g., shading effect, the roughness of surface, the increase in potential), the chemical changes (i.e., the release of additives, the increase of oxidative stress) contributed to the inhibitory effects of MPs on microalgae, but the deciding factor remains to be further systematically explored.