Paraglacial lagoons of Svalbard: emerging ecosystems at the Arctic Land-Sea interface

Rapid glacier retreat across the Arctic is transforming coastal landscapes and generating a growing number of previously non-existent aquatic habitats. In Svalbard, this process has led to the formation and expansion of coastal lagoons, including a substantial proportion of newly emerged paraglacial systems. Despite their increasing abundance, these environments remain poorly represented in Svalbard research and monitoring programs, and their ecological and biogeochemical significance is only beginning to be recognized. Herein we synthesize current knowledge of Svalbard coastal lagoons, integrating perspectives from geomorphology, hydrology, ecology, and biogeochemistry. We propose that these systems form a developmental continuum, ranging from newly formed, glacier-influenced basins to more stable and biologically structured lagoons. Observations from recently studied lagoon systems indicate strong environmental gradients, spatial heterogeneity and dynamic hydrological conditions that support diverse and evolving biological communities across trophic levels. Emerging evidence suggests that Arctic lagoons may function as biogeochemical reactors, including potential sources of methane, while also acting as accumulation zones for contaminants such as microplastics and persistent organic pollutants. At the same time, their ecological role – as biodiversity hotspots, transitional habitats, or stepping-stones for species redistribution – remains insufficiently understood. We identify key knowledge gaps related to lagoon formation, physical dynamics, ecosystem development, and greenhouse gas fluxes and outline a research roadmap for coordinated interdisciplinary investigations. We argue that Svalbard lagoons represent a rapidly expanding nature type that provides a unique opportunity to study ecosystem development under climate change and should be integrated into future Arctic research and assessment frameworks.