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Microplastics: toxicity and Bioacumulation at the first trophic levels of the food chain
Summary
Using standardized ecotoxicity tests, researchers exposed the water flea Daphnia magna and the alga Desmodesmus subspicatus to polyethylene microspheres — the kind widely used in cosmetic exfoliants — and found measurable harm at low concentrations. Crucially, adult Daphnia were ten times more sensitive than juveniles, and microscopy confirmed that microplastics physically accumulated in the animals' digestive tracts, showing that contamination begins at the very base of the food chain.
Microplastics are dispersed in nature in all planetary compartments, and can be found in the most remote places of the Ecosystem. They are currently indicated as markers of the Anthropocene, a geological era caused by human changes on the globe. Even though it is found in all environmental compartments, there are still gaps in scientific knowledge about its real impact on living cells and their dynamics, including in the human organism. Therefore, the objective of the study is to use an internationally standardized and standardized method in representative organisms of the ecosystem, thus using the acute and chronic ecotoxicity test with the microcrustacean Daphnia magna and for the algae Desmodesmus subspicatus, respectively, against polyethylene microspheres, a thermoplastic widely used as an exfoliation product and applied in various cosmetics and hygiene materials. They were tested in neonates according to the reference standards, but 30-day-old adult organisms were also exposed. The results obtained, for the crustaceans, show the Effective Concentration that causes effect in 50% of the organisms (EC50%), with 95% confidence of 0.07 g/L and a DSC – Observed effect concentration of 0.025 g/L for neonates. For the adult specimens, 0.025 g/L of EC50 and 0.0025 g/L of DSC were found, showing that the pups are 10x more resistant to plasticizers compared to the adults. For the algae test, the results showed a DSC of 0.05 g/L, inhibiting 20.12% of algae growth compared to the control. In the optical microscope of the crustaceans after exposure, it showed bioaccumulation of the polyethylene microsphere in the carapace and digestive tract of the bioindicator, showing that the impact of microplastics begins in the first trophic levels of the food chain.