The mortar-and-pestle digestive system of oceangoing krill can grind microplastics into even tinier particles, with potentially hazardous consequences, The Guardian reports. Researchers fed krill microplastic beads, a pollutant common in the world’s oceans, and then looked for digested particles in the creatures’ bodies and feces. They found that the krill broke beads down into “nanoplastic” fragments that were up to 94% smaller than the 32-micron-wide particles. The conversion of microplastics into nanoplastics could make it easier for other, smaller sea creatures to inadvertently consume the pollutants. Writing in Nature Communications, the authors say that nanoplastic fragments may also pass more easily into other areas of sea creatures’ bodies and have toxic effects.