The 'Lifeboat Hypothesis': Aquatic Microplastics in a Warming World-Climate-Resilient Refugia for Bacterial Pathogens.

The Lifeboat hypothesis proposes that microplastics act as mobile microbial refugia, buffering environmental stress and enabling persistence, adaptation and dispersal of microorganisms, including pathogens and antimicrobial resistance (AMR) determinants. Microplastic-associated biofilms (the plastisphere) mitigate UV radiation, osmotic stress and environmental fluctuations, while promoting stress responses and horizontal gene transfer. Ocean circulation then facilitates long-range transport of these communities, linking distant ecosystems. Climate-driven cryosphere thaw may further introduce ancient microorganisms into the contemporary plastisphere ('paleo-plastisphere'), where they are captured and redistributed. In parallel, ingestion by marine organisms provides a biological bypass that enhances microbial survival and accelerates trophic transfer. Collectively, these processes position microplastics as dynamic vectors of microbial connectivity, with implications for infectious disease exposure, biosecurity leakage and transboundary AMR dissemination under global environmental change.