Global change reshapes marine microbial communities, functions and One Health outcomes

Marine microorganisms underpin primary production, biogeochemical cycling and host-associated symbioses, supporting climate regulation, coastal protection, fisheries and other ecosystem services. Rapid global change, including ocean warming and marine heatwaves, acidification, deoxygenation, eutrophication, pollution and overuse reshape microbial communities and their functions across marine habitats. These changes can alter carbon, nitrogen and sulfur cycles, promote microbialization and harmful algal blooms, disrupt host-microbiome associations and modify pathogen and antimicrobial resistance dynamics, collectively amplifying the ecological and societal impacts of global change. This Review frames marine microbiomes as cross-scale mediators that translate external pressures, including climate change, pollution, eutrophication and habitat degradation, into altered microbial metabolism, biogeochemical fluxes, host-associated health outcomes, ecosystem service consequences and broader One Health risks. We synthesize shared mechanisms and cross-habitat patterns, highlight cases in which microbiome interventions and stewardship could mitigate impacts and/or accelerate recovery, and outline management options ranging from the reduction of local stressors to emerging microbiome stewardship approaches in ecosystem restoration. Building upon this, we outline pathways for embedding marine microbiome science into globally coordinated One Health strategies, operational management protocols and financing frameworks that align economic incentives with long-term ecosystem and public health outcomes.