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Trophic transfer and egestion dynamics of microplastics in the Brachionus-Asplanchna rotifer system
Summary
Scientists studying tiny freshwater creatures found that when one organism ate microplastic particles and was then eaten by a predator, the plastic passed up the food chain—but didn't stick around for long. Both the prey and predator flushed the microplastics out of their systems within a day or two, suggesting these particles may pass through simple food webs rather than building up over time. While this is encouraging news, the study looked at a very basic two-species system in a lab, so more research is needed to understand what happens in real ecosystems—and eventually, in the foods humans eat.
Abstract Microplastics have become a pervasive contaminant in freshwater ecosystems worldwide, raising concerns about their impact on aquatic life, especially zooplankton, which play a pivotal role in freshwater food webs. Despite their ecological importance, knowledge on how microplastics move through predator–prey interactions in microscopic communities remains limited. We investigated this question using a classic freshwater system: the filter-feeding rotifer Brachionus caudatus and its predator, Asplanchna brightwellii . Specifically, we asked: How efficiently do these organisms ingest and eliminate microplastics, and to what extent are the particles transferred across trophic levels? We exposed B. caudatus to three concentrations of 1 µm fluorescent polystyrene microspheres (0.1, 0.5, and 1.0 µg ml −1 ) for 24 h, then fed this contaminated prey to A. brightwellii predators. Using fluorescence microscopy, we tracked the fate of the microplastics over 48 h in both species. Both rotifers readily consumed the microspheres, and they also eliminated them efficiently. Fluorescence intensity declined rapidly in both prey and predator, with minimal retention after 24–48 h. While predators initially accumulated more than twice the fluorescence of their prey (confirming trophic transfer), this accumulation was short-lived. The rapid clearance suggests that in this simple food chain, 1 µm polystyrene microspheres do not biomagnify. Our findings reveal that these microplastics behave more like transient contaminants than persistent pollutants in rotifer communities, offering new insights into how microplastics flow through freshwater food webs at the microscopic scale.