Microplastic exposure reduces seed germination in a coastal plant

Plastic contamination presents major environmental threats through its degradation into micro-sized particles that are harmful to a variety of organisms, including plants. Among terrestrial habitats, coastal dunes are likely some of the most plastic-polluted, but very few studies thus far have examined microplastic effects on wild plants native to this habitat. Moreover, current research on microplastics has limited environmental relevancy due to the common use of homogenously shaped un-weathered microplastics in exceeding concentrations. Our research examined the effects of microplastics from biodegradable and non-biodegradable origin, in their pristine (raw) and weathered form, at a concentration of 10⁶ particles per ml, on the native coastal plant Cutandia maritima. We first synthesized engineered microplastics of high environmental relevancy from bulk plastic products. Then, we exposed C. maritima plants to the microplastics in the soil. While no effect was found on the plants following chronic exposure to all microplastic types, weathered plastic reduced seed germination after exposure of the mother plants, suggesting epigenetic modifications might have an effect at the embryo stage. In contrast, direct exposure of microplastics, specifically polylactic acid, facilitated seeds germination. Our results highlight the importance of studying the effects of microplastic on seed germination and raise the ongoing ecological consequences of environmental microplastic coastal contamination, which should be taken into account in regulatory and environmental assessments.