Bioaccumulation, transfer, and impacts of microplastics in aquatic food chains

Plastics have become a pervasive global contaminant since the mid-20th century, causing harm to organisms at all levels. Preventative measures to reduce plastic pollution and awareness-raising campaigns about the damaging effects of plastic debris on the environment and its inhabitants are crucial; however, most plastic assessments focus on singular trophic levels. Microplastics, tiny plastic particles ranging from 25 μm to 5 mm, have emerged as a widespread form of pollution found in ecosystems worldwide. They can enter the environment directly or through the breakdown of larger plastic debris and are thought to be mistaken for food by foraging animals. This leads to microplastics circulating through ecosystems via direct and indirect consumption, ultimately impacting even higher-order predators. Here, we assess the impacts of microplastics on Chlorophyll a concentrations, algal community structure, copepod survivorship, and fish behavior in experimental trials, in addition to simulated top-predator foraging success on plastic-exposed fish. Our results indicate that microplastics have detrimental effects on algal growth and copepod survival. We also observed the trophic transmission of small plastic spheres from copepods to fish predators, highlighting a concerning pathway for microplastic pollution within aquatic ecosystems, where fish consumed plastics through direct and indirect means. Primary consumers, like copepods, face dual pressures from top-down forcing, as they are preferred over plastic particles as food sources, and bottom-up resource depletion, as algal food supplies can be limited by microplastic exposure. Our findings demonstrate the system-wide impacts that can occur when microplastics are included in food chains and underscore the urgent need for comprehensive strategies to mitigate the entry of plastic debris into aquatic ecosystems.