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Ecological risk of microplastics in Antarctic coastal systems: when polymer composition and trophic exposure outweigh low environmental concentrations
Summary
Scientists studying an Antarctic bay found that even though microplastic levels there are very low compared to more populated areas, the *type* of plastic matters just as much as the amount—some plastics are more toxic to marine life than others, and tiny sea creatures showed stress responses even at these low levels. This matters because it suggests that "low contamination" doesn't automatically mean "low risk," a lesson that applies to how we assess microplastic exposure everywhere, including in the food chains that eventually reach our own plates.
Microplastics (MPs) are emerging contaminants of concern in the Antarctic region, yet ecological risk assessments remain scarce and often rely on concentration-based metrics. Here, we present an integrative ecological risk assessment framework combining mass-based environmental exposure, polymer-specific hazard, species sensitivity distributions, and zooplankton bioassays. This framework is applied to Potter Cove (25 de Mayo / King George Island, Antarctica), a coastal system influenced by research station activities. Measured environmental concentrations (MEC) ranged from <0.001 to 0.018 mg MPs L in seawater and from <0.0001 to 0.0002 mg MPs g dry weight in sediments, based on conservative, particle mass estimates. Ecotoxicological thresholds were derived from published species sensitivity distributions and local zooplankton bioassays conducted under controlled laboratory conditions, providing complementary, organism-level evidence rather than direct validation. Polymer composition was dominated by polyester, cellulosic materials, and styrene-based polymers, indicating a relatively high hazard profile based on monomer classifications. Risk quotients (RQ; MEC/predicted no-effect concentration, PNEC = 0.18 mg L) suggested low risk based on mass concentrations alone. In contrast, the potential ecological risk index (PERI) suggests spatial variability, with higher values near anthropogenic sources. Zooplankton bioassays supported sublethal responses at environmentally relevant exposures, indicating that exposure patterns may not be fully captured by concentration-based metrics. These findings suggest that even low-contamination Antarctic systems may exhibit sensitivity under specific exposure conditions. Overall, this framework should be interpreted as a screening-level, exploratory approach to identify relative risk patterns rather than provide definitive risk estimates.