Turning microplastics into nanoplastics through digestive fragmentation by Antarctic krill

TLDR

Microplastics (<5 mm) are a major environmental concern, yet little is known about their degradation through ingestion, and prior feeding studies show that spherical microplastics either pass unaffected and are excreted or are small enough for translocation. The study exposes Antarctic krill to microplastics under acute static renewal conditions to demonstrate physical size alteration of ingested particles. Antarctic krill fragment ingested microplastics from 31.5 µm down to <1 µm, creating a new pathway that allows particles to cross physical barriers or be egested as triturated fragments, indicating that laboratory feeding studies may oversimplify zooplankton–plastic interactions and highlighting krill’s role in plastic biogeochemical cycling.

Abstract

Microplastics (plastics <5 mm diameter) are at the forefront of current environmental pollution research, however, little is known about the degradation of microplastics through ingestion. Here, by exposing Antarctic krill (Euphausia superba) to microplastics under acute static renewal conditions, we present evidence of physical size alteration of microplastics ingested by a planktonic crustacean. Ingested microplastics (31.5 µm) are fragmented into pieces less than 1 µm in diameter. Previous feeding studies have shown spherical microplastics either; pass unaffected through an organism and are excreted, or are sufficiently small for translocation to occur. We identify a new pathway; microplastics are fragmented into sizes small enough to cross physical barriers, or are egested as a mixture of triturated particles. These findings suggest that current laboratory-based feeding studies may be oversimplifying interactions between zooplankton and microplastics but also introduces a new role of Antarctic krill, and potentially other species, in the biogeochemical cycling and fate of plastic.