SUMMARY: This study found that krill were breaking down microplastic beads into smaller and smaller pieces in their digestive system. The krill were divided into two groups, one eating 80% plastic beads with 20% algae, the other eating 20% plastic beads and 80% algae. The type of plastic used was polyethylene, the most common type of plastic. Researchers made sure that it wasn’t just the digestive enzymes that made the beads smaller, but the krill’s digestive system as a whole (see page 3). After feeding the krill for 4 days on this special plastic diet, plastic particles of all different sizes were found throughout the krill’s digestive system (mouth, stomach) as well as in their tissue (see Fig. 3 on page 4). There still needs to be more research done on how these plastic pieces are being degraded and if there are any toxic effects on plankton.
LESSON COMMENTS: This article is easy to read and the experiment may even be replicated in a classroom. A class could collect samples from ponds, allow the microorganisms to grow in it and then feed them plastic micro-beads filtered out from face wash. This article can be read alongside other articles about microplastics.
For younger students in middle school, this could be a good way to introduce the digestive system, invertebrate digestion, and scientific method. One could also use this article to talk about environmental impacts and pollution.
A. L. Dawson, S. Kawaguchi, C. K. King, K. A. Townsend, R. King, W. M. Huston, and S. M. B. Nash, “Turning microplastics into nanoplastics through digestive fragmentation by Antarctic krill,” Nature Communications, vol. 9, no. 1, 2018.