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Microplastic ingestion affects hydrogen production and microbiomes in the gut of the terrestrial isopod Porcellio
Linda Hink1, Anja Holzinger2, Tobias Sandfeld3
1Institute of Microbiology, Leibniz University Hannover, Hannover, Germany.
Abstract:
Microplastic (MP) is an environmental burden and enters food webs via ingestion by macrofauna, including isopods (Porcellio scaber) in terrestrial ecosystems. Isopods represent ubiquitously abundant, ecologically important detritivores. However, MP-polymer specific effects on the host and its gut microbiota are unknown. We tested the hypothesis that biodegradable (polylactic acid [PLA]) and non-biodegradable (polyethylene terephthalate [PET]; polystyrene [PS]) MPs have contrasting effects on P. scaber mediated by changes of the gut microbiota. The isopod fitness after an 8-week MP-exposure was generally unaffected, although the isopods showed avoidance behaviour to PS-food. MP-polymer specific effects on gut microbes were detected, including a stimulation of microbial activity by PLA compared with MP-free controls. PLA stimulated hydrogen emission from isopod guts, while PET and PS were inhibitory. We roughly estimated 107 kg year-1 hydrogen emitted from the isopods globally and identified their guts as anoxic, significant mobile sources of reductant for soil microbes despite the absence of classical obligate anaerobes, likely due to Enterobacteriaceae-related fermentation activities that were stimulated by lactate generated during PLA-degradation. The findings suggest negative effects of PET and PS on gut fermentation, modulation of important isopod hydrogen emissions by MP pollution and the potential of MP to affect terrestrial food webs.
Insights
Microplastics (MPs) impact terrestrial ecosystems. Biodegradable polylactic acid (PLA) MPs stimulate gut microbes, while polyethylene terephthalate (PET) and polystyrene (PS) MPs inhibit them, affecting hydrogen emissions.
Area of Science:
- Environmental Science
- Microbiology
- Ecotoxicology
Background:
- Microplastics (MPs) are pervasive environmental pollutants.
- Terrestrial detritivores like isopods (Porcellio scaber) ingest MPs, potentially affecting food webs.
- MP-polymer specific effects on host physiology and gut microbiota remain largely unknown.
Purpose of the Study:
- To investigate the contrasting effects of biodegradable (PLA) and non-biodegradable (PET, PS) MPs on the terrestrial isopod P. scaber.
- To determine if MP-induced changes in the gut microbiota mediate these effects.
- To assess the impact of MPs on isopod fitness and hydrogen emissions.
Main Methods:
- Exposure of P. scaber to PLA, PET, and PS MPs for 8 weeks.
- Monitoring of isopod fitness and feeding behavior.
- Analysis of gut microbial activity and gas emissions (hydrogen).
Main Results:
- Isopod fitness was generally unaffected, but avoidance behavior towards PS was observed.
- PLA MPs stimulated gut microbial activity and hydrogen emission.
- PET and PS MPs inhibited gut fermentation and hydrogen emission.
- Isopod guts identified as significant sources of reductant for soil microbes.
Conclusions:
- MP-polymer type influences gut microbiota and associated physiological processes in terrestrial isopods.
- PLA MPs may alter soil microbial processes via stimulated fermentation.
- PET and PS MPs negatively affect gut fermentation, potentially impacting terrestrial ecosystems.
- MP pollution can modulate crucial ecological functions, such as hydrogen emissions, in detritivores.
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