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

Abstract

Microplastics (MP) are pervasive in the environment. There is ample evidence of negative MP effects on biota in aquatic ecosystems, though little is known about MP effects in terrestrial ecosystems. Given numerous entry routes of MP into soils, soil organisms are likely to be exposed to MP. We compared potential toxicological effects of MP from (i) low-density polyethylene (LDPE) (mean diameter ± standard deviation: 57 ± 40 µm) and (ii) a blend of biodegradable polymers polylactide (PLA) and poly(butylene adipateco-terephthalate) (PBAT) (40 ± 31 µm) on the reproduction and body length of the soil-dwelling bacterivorous nematode Caenorhabditis elegans. Feed suspensions without (control) or with MP (treatments) at concentrations of 1, 10, and 100 mg MP L −1 were prepared and nematodes were exposed to those suspensions on agar plates until completion of their reproductive phase (∼6 days). Using Nile red-stained PLA/PBAT MP particles and fluorescence microscopy, we demonstrated the ingestion of MP by C. elegans into pharynges and intestines. Under MP exposure, nematodes had fewer offspring (up to 22.9%) compared to nematodes in the control group. This decline was independent on the plastic type. We detected a tendency toward greater decreases in offspring at higher concentrations. Despite hints of negative effects on nematode body length under MP exposure, we could not derive a consistent pattern. We conclude that in MP-contaminated soils, the reproduction of nematodes, central actors in the soil food web, can be affected, with potentially negative implications for key soil functions, e.g., the regulation of soil biogeochemical cycles.

Effects of Different Microplastics on Nematodes in the Soil Environment: Tracking the Extractable Additives Using an Ecotoxicological Approach

“…Notably, most of these studies except only four papers 29,[62][63][64] have adopted spherical PS particles as target material, and only two papers are utilizing field-collected or secondary-treated particles instead of purchased beads or pellets. 62,64 Although C. elegans has been suggested as a standard soil test species, 61,65 there is only one study conducting tests in soil media, 28 and 25 studies were performed using liquid media such as K-medium and M9 buffer solution (Table S2). On the other hand, six papers report size-dependent inhibitory effects of microplastic on C. elegans, [27][28][29][30]66,67 showing a tendency toward toxic effects that can be increased by smaller sizes in ranges of 0.05 to 0.2 μm, 27 0.1 to 6.0 μm, 67 and 0.1 to 5.0 μm.…”

Microfluidic Electric Egg-Laying Assay and Application toIn-vivoToxicity Screening of Microplastics usingC. elegans

“…Although some researchers have reported a negative effect of microplastics on C. elegans length 10,11,22 , others have shown similar results in terms of the non-correlating effect of microplastics on the worms’ length. 24…”

“…10,22,23 Microplastics negatively affected C. elegans phenotypical behaviours such as locomotion and body bend frequency as well as its growth and reproduction. 9-12,22-24…”

“…10,22,23 Microplastics negatively affected C. elegans phenotypical behaviours such as locomotion and body bend frequency as well as its growth and reproduction. [9][10][11][12][22][23][24] Lei et al 11 studied the effects of exposing C. elegans to 1 mg/L of 0.1-5μm polystyrene microparticles, using locomotory behaviours, growth, and lifespan as toxicity indicators. Their investigations demonstrated that 1μm particles significantly deteriorated the survival and growth rate and caused oxidative damage to cholinergic and GABAnergic neurons, which was ameliorated by natural antioxidants such as curcumin.…”

Effects of Different Microplastics on Nematodes in the Soil Environment: Tracking the Extractable Additives using an Ecotoxicological Approach

“…Notably, most of these studies except only four papers 29,[62][63][64] have adopted spherical PS particles as target material, and only two papers are utilizing field-collected or secondary-treated particles instead of purchased beads or pellets. 62,64 Although C. elegans has been suggested as a standard soil test species, 61,65 there is only one study conducting tests in soil media, 28 and 25 studies were performed using liquid media such as K-medium and M9 buffer solution (Table S2).…”