Microplastic ingestion affects hydrogen production and microbiomes in the gut of the terrestrial isopod Porcellio scaber

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.

Interkingdom interaction: the soil isopod Porcellio scaber stimulates the methane-driven bacterial and fungal interaction

“…Nevertheless, these microorganisms may represent epibionts. It remains to be determined whether the hitchhiking microorganisms that re-colonized the γ-irradiated soil were derived from the gut (through fecal deposition) [ 20 ]; and/or body surface of P. scaber , and whether the microorganisms were passively (i.e., unintentional dispersal) and/or actively (i.e., reciprocal selection of microorganism-macroinvertebrate) transported. Regardless of the source and exact transfer mechanism, it is evident that P. scaber facilitated microbial dispersal.…”

“…Specifically, P. scaber activity (e.g., feeding and foraging habits, fecal deposition) may also induce compositional shifts in the soil microbial community, having an indirect effect on microbially-mediated organic matter decomposition [ 4 ]. Although recent work began to shed light on microbe-macroinvertebrate interaction in terrestrial ecosystems [ 20 ], virtually nothing is known on how (sub-)surface-dwelling macroinvertebrates exert an impact on other non-CO 2 primary greenhouse gases, particularly methane.…”