Impact of glacial meltwater on prokaryotic dynamics in high Arctic fjords

Arctic fjords are among the most sensitive ecosystems, particularly affected by rapid cryospheric changes. One of the most prominent consequences of global warming in these regions is the increasing input of glacial meltwater, which alters the physical and chemical structure of fjord systems and profoundly affects prokaryotic (bacterial and archaeal) communities. Despite these changes, the impacts on prokaryotic communities, central players in biogeochemical cycles and ecosystem functioning, remain poorly understood. This review synthesizes current knowledge on how glacial meltwater influences prokaryotic dynamics in Arctic fjords pelagic ecosystems, with a focus on community composition, functional potential, and biogeochemical implications. We explore how freshwater influx affects salinity, turbidity, nutrient fluxes, and organic matter availability drives prokaryotic selection processes. Critical knowledge gaps remain, particularly in linking taxonomic shifts to changing ecosystem dynamics and predicting long-term ecological trajectories under the continued intensification of meltwater input. We emphasize the urgent need for integrative, multi-seasonal studies combining molecular tools, biogeochemical measurements, and modeling approaches to fully understand prokaryotic responses to ongoing environmental change in Arctic fjords.