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Minimal contribution of bioerosion in the deterioration of biodegradable plastics in the marine environment: evidence from laboratory and field experiments
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Scientists tested whether ocean critters like tiny shrimp-like amphipods and sea snails speed up the breakdown of "biodegradable" plastic by biting it into pieces. Turns out, these creatures aren't the main reason biodegradable plastics disappear in the ocean—time and environmental exposure matter far more—but the study did find that when invertebrates nibble on plastic, they end up with microplastics in their bodies and waste, raising concerns about how these particles might move up the food chain toward us.
Biodegradable, bio-based plastics are widely used alternatives to conventional plastics; however, understanding their degradation under natural marine conditions remains incomplete. Previous work has highlighted the potential of bioerosion by marine invertebrates in the fragmentation of plastic films. This study investigated the role of bioerosion by marine invertebrates in the deterioration of three biodegradable (one PLA/PBAT (‘Bio1’) and two Mater-bi formulations (‘Bio2’, ‘Bio3’)) and one conventional polyethylene (PE) film, using complementary field and laboratory experiments. In a temperate coastal experiment, PE and biodegradable films were deployed for 9 weeks (-1.5m depth), with and without invertebrate exclusion chambers. Biodegradable films lost ≥96% mass regardless of exclusion treatment, while there was no change in PE-film mass. While acknowledging material-specific differences in in-situ degradation profiles, statistical analysis identified exposure duration as the dominant driver (η 2 partial = 0.946); while exclusion treatment had minimal effect (η 2 partial < 0.0001). Biodegradable films had micrometre-scale pitting, but no evidence of invertebrate bite marks. Laboratory experiments exposed Bio1, PE and natural food (kelp) discs to amphipods ( Marinogammarus marinus ; detritivore ‘shredders’) and periwinkles ( Littorina littorea ; omnivorous grazer) for 21-days. Plastic discs showed evidence of bioerosion by amphipods (Bio1-film 60 ± 16%; PE-film: 20 ± 6% of disc segments), but not by periwinkles. However, Bio1 and PE microplastics were detected in tissue and faeces of both invertebrates, with amphipods containing 3.5-fold, and 31-fold more microplastics, respectively, than periwinkles. Collectively, findings demonstrate that while marine invertebrates can bioerode test materials and generate microplastics, their contribution to degradation under natural conditions is minor.
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Biodegradable microplastics: Uptake by and effects on the rockpool shrimp Palaemon elegans (Crustacea: Decapoda)
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Researchers fed shrimp three types of microplastics, including two biodegradable kinds (PLA and PHBV) and conventional polyethylene, and found that all types were readily eaten. Surprisingly, the biodegradable microplastics stayed in the shrimp's stomachs longer than the conventional plastic, and all types triggered stress-related enzyme activity. This suggests that biodegradable plastics are not necessarily safer for marine life than conventional plastics once they break down into microplastic-sized particles.
Biodegradable and Petroleum-Based Microplastics Do Not Differ in Their Ingestion and Excretion but in Their Biological Effects in a Freshwater Invertebrate Gammarus fossarum
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This study compared the ingestion and effects of biodegradable (polyhydroxybutyrate) versus petroleum-based (polymethylmethacrylate) microplastic particles in freshwater amphipods. Both types were ingested at similar rates, suggesting that labeling a plastic as biodegradable does not reduce its short-term risk of ingestion and physical harm to aquatic invertebrates.
Microplastic formation during degradation: bioplastics vs conventional plastics
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"Biodegradable" plastics are often marketed as a safer, eco-friendly choice, but this study found they can actually break down into just as many microplastic particles as regular plastics like LDPE and PP, sometimes more. That matters because these tiny plastic bits can end up in soil, water, and eventually our food, so switching to bioplastics alone may not reduce your microplastic exposure.
Fate of plastic in the environment: From macro to nano by macrofauna.
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This review examines the role that animals themselves play in breaking large plastic items down into smaller fragments through feeding, digestion, and mechanical action. Researchers found that invertebrates, fish, birds, and mammals all contribute to physical fragmentation of plastics, accelerating the production of microplastics in the environment. The findings suggest that biological fragmentation is an underappreciated pathway in the plastic degradation cycle.
Microbial degradation and the persistence paradox of conventional and biodegradable microplastics
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"Biodegradable" plastics are often marketed as an eco-friendly alternative to regular plastic, but this review of existing research finds that in real-world conditions, many of them don't actually fully break down—they just crumble into smaller microplastic pieces, just like conventional plastic does. This matters because these lingering microplastic fragments (regardless of what type of plastic they came from) can end up in soil, water, food, and ultimately our bodies, meaning switching to "biodegradable" products may not reduce microplastic exposure as much as people assume.
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