Daphnia magna exhibit a preference for microplastic fibers that are black in the presence of olfactory cues.

The presence of small pieces of plastic, termed Microplastics (MP), in the environment is a growing ecological concern, especially for the health of organisms that ingest them, but little is known about which MP characteristics influence their likelihood of ingestion. A small freshwater invertebrate, Daphnia magna, was used to determine if the color or odor of MPs influenced feeding preference in this species. We hypothesized that D. magna would have a preference for green MPs that resembled the color and odor of their algal food source. Experiments exposing D. magna to mixtures of different colored MP fibers, or mixtures of pristine and biofouled MP fibers were conducted. The number of ingested fibers in each intestine was quantified under a fluorescence microscope, using the signature autofluorescence of MP colors, to determine if D. magna exhibited a preference for MP based on color or odor. Our results suggest that D. magna do not exhibit a preference for MPs based on color alone. However, in the presence of odorants (biofouled MPs) a significant preference for black MP over green MP is revealed, suggesting that olfactory cues affect feeding behavior. Our results offer insight into the relationship between MP color and odor, and feeding preference, in D. magna. [ABSTRACT FROM AUTHOR]