Field evidence for transfer of plastic debris along a terrestrial food chain

Abstract

Although plastic pollution happens globally, the micro- (<5 mm) and macroplastic (5–150 mm) transfer of plastic to terrestrial species relevant to human consumption has not been examined. We provide first-time evidence for micro- and macroplastic transfer from soil to chickens in traditional Mayan home gardens in Southeast Mexico where waste mismanagement is common. We assessed micro- and macroplastic in soil, earthworm casts, chicken feces, crops and gizzards (used for human consumption). Microplastic concentrations increased from soil (0.87 ± 1.9 particles g−1), to earthworm casts (14.8 ± 28.8 particles g−1), to chicken feces (129.8 ± 82.3 particles g−1). Chicken gizzards contained 10.2 ± 13.8 microplastic particles, while no microplastic was found in crops. An average of 45.82 ± 42.6 macroplastic particles were found per gizzard and 11 ± 15.3 macroplastic particles per crop, with 1–10 mm particles being significantly more abundant per gizzard (31.8 ± 27.27 particles) compared to the crop (1 ± 2.2 particles). The data show that micro- and macroplastic are capable of entering terrestrial food webs.

Towards an ecology of soil microplastics

“…In addition to simply moving microplastics, biotic activities may also place them in pedological contexts they would rarely if ever otherwise occupy. Earthworms incorporate microplastics into their casts and burrow walls (Huerta Lwanga, Gertsen, et al, ; Huerta Lwanga et al, ; Huerta Lwanga, Mendoza Vega, et al, ; Prendergast‐Miller et al, ; Rillig, Ziersch, et al, ). These casts and burrows comprise a unique microhabitat that soil ecologists term the drilosphere (Andriuzzi, Bolger, & Schmidt, ; Sharma, Chandra, & Kanta, ).…”

“…Though plastics obviously cannot actively hitchhike, they can still be passively dispersed on or inside soil organisms (Maaß et al, 2017;Rillig, Ziersch, et al, 2017;Zhu, Bi, et al, 2018). Although dispersal by springtails and mites has so far only been demonstrated in Petri dish arenas (Maaß et al, 2017;Zhu, Bi, et al, 2018), microplastics have been found in field-collected earthworm casts (Huerta Lwanga, Mendoza Vega, et al, 2017). Within soil pores, springtail movement may also facilitate influxes of small microplastic particles (Kim & An, 2019 In addition to simply moving microplastics, biotic activities may also place them in pedological contexts they would rarely if ever otherwise occupy.…”

“…Within soil pores, springtail movement may also facilitate influxes of small microplastic particles (Kim & An, 2019 In addition to simply moving microplastics, biotic activities may also place them in pedological contexts they would rarely if ever otherwise occupy. Earthworms incorporate microplastics into their casts and burrow walls (Huerta Lwanga, Gertsen, et al, 2017;Huerta Lwanga et al, 2016;Huerta Lwanga, Mendoza Vega, et al, 2017;Prendergast-Miller et al, 2019;Rillig, Ziersch, et al, 2017).…”

“…However, experiments showing significant harm sometimes do so only with microplastic concentrations beyond what is common in the current environment (Cunningham & Sigwart, ; Lenz, Enders, & Gissel, ; Phuong et al, ). Trophic transfer of microplastics to higher levels of the food web, commonplace in marine systems (Carbery, Connor, & Thavamani, ; Nelms, Galloway, Godley, Jarvis, & Lindeque, ; Setälä, Fleming‐Lehtinen, & Lehtiniemi, ), has so far been only indirectly shown in terrestrial environments (Huerta Lwanga, Mendoza Vega, et al, ). If microplastics can be transferred from prey to predators in soil, it could result in microplastics escaping the confines of soil and spreading throughout the above‐ground food web, via the many terrestrial animals (including vertebrates) that consume soil invertebrates, but requires further investigation.…”

Microplastics Effects on Reproduction and Body Length of the Soil-Dwelling Nematode Caenorhabditis elegans

“…Translocation of MP by earthworms (Huerta Lwanga et al, 2017a;Rillig et al, 2017b) and collembola (Maaß et al, 2017) could increase the exposure of other soil-dwelling species to MP. In addition, evidence on the accumulation of MP from soil to earthworms to chicken feces (Huerta Lwanga et al, 2017b) indicates that MP may enter terrestrial food webs through trophic transfers.…”