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Microplastics alter the fate of inland-derived microbial contaminants transported into coastal environments by tropical cyclones
Summary
When hurricanes flood coastal areas, they wash bacteria carrying antibiotic-resistance genes into the ocean—and new research shows microplastics act like rafts that let these germs survive twice as long by forming protective biofilms. This means swimming or fishing in coastal waters after a major storm could carry hidden risks for weeks or months longer than health officials currently account for, since standard water quality tests may miss this microplastic-shielded bacteria.
Tropical cyclones transport diverse contaminants, including microbial contaminants and microplastics, from inland to coastal environments. However, the fate of these inland-derived contaminants after transport remains poorly understood. Here, we investigated the mechanisms by which microplastics affect the fate of inland-derived microbial contaminants in coastal waters. Field observations following Hurricane Milton revealed substantial transport of microplastics from inland areas to Florida’s Gulf Coast, where antimicrobial resistance genes (ARGs) associated with particles larger than 25 µm accounted for approximately 25% of the total ARG abundance introduced during the hurricane event. We confirmed that biofilm formation on microplastics reduced the decay rates of inland-derived bacteria to about half under simulated coastal conditions. We also confirmed that inland-derived bacteria coexisted with indigenous marine bacteria in coastal environments, facilitated by microplastics, for extended periods (weeks to months), posing a potential risk of horizontal gene transfer of ARGs from inland to coastal environments. Consequently, microplastics may extend the impact of storm-introduced microbial threats beyond what is captured by conventional fecal indicator bacteria-based assessments. This study highlights the need to reconsider microbial water quality recovery in coastal environments by accounting for particle-associated processes following extreme events.