Are Microplastics Tasty?

Photo credit: Dr. Jeroen Ingels, @jeroeningels and @meiolab on Instagram

More research has found microplastics in the digestive tracts of marine organisms, suggesting that a large number of animals are encountering microplastics in the ocean. However, no works that I'm aware of have attempted to answer the question posed by this week's blog: are microplastics tasty? If microplastics are ingested by animals, then the animals are either actively eating microparticles or the particles are inconspicuously entering their bodies, likely through accidental non-selective feeding practices (think a baleen whale attempting to filter water through its comb but some particles entering its gut that it didn't want). I expect that non-selective feeding practices cause microplastics ingestion by megafauna, along with consumption of prey items that have consumed microparticles. Meiofauna, given their size, however, should be less likely to accidentally consume microparticles when they are feeding, but there is no research that has tested this theory.

Fueser et al. (2019) started to address this question by determining that the ingestion of microplastics by nematodes is based on the buccal sizes of the animals. Nematodes are not eating microplastics larger than their mouth openings, which may make you question why Fueser and colleagues did the study, but remember that prior to this work we didn't know how microplastics were getting into nematodes' digestive tracts. There are a number of different feeding types within the nematode taxa (there is some debate about how many and the specific classifications, with at least 3 different classification systems), which suggests that some nematodes may be more likely to ingest microplastics than others. For example, some nematodes are bacterivores (bacteria-feeders), and microplastics usually have microbial colonies living on the surface. Therefore, I would expect that bacterivores are more likely than other feeding types to ingest microplastics, because they are attempting to eat the bacteria on the surface and accidentally consume entire microparticles. Other nematode feeding types, like predatory nematodes (shown to the right), should not be consuming microplastics unless their prey items have already ingested the particles. As part of my future work on nematodes and microplastics I will be conducted experiments to assess which feeding types and nematode genera are consuming microplastics in coastal sediments, and I hope to parse out whether or not the nematodes are attempting to eat the surface bacteria or if they are actively eating the microplastics.


References:
Fueser, H., Muller, M-T., Weiss, L., Hoss, S., & Traunspurger, W. (2019). Ingestion of microplastics by nematodes depends on feeding strategy and buccal cavity size. Environmental Pollution, 255, 113227.

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