SIESTA Project: Svalbard summer 2025 expedition report

Microbial dormancy plays an important role in the persistence, dispersal, and functioning of microbial communities in moderate to extreme environments. The activity or inactivity of microbial communities also has implications for rates of biogeochemical transformations and thus elemental stocks and redox conditions. Microbial communities inhabiting glacier surface environments encounter harsh and variable environmental conditions including nutrient limitation, low temperatures, and light availability across various micro-habitats including cryoconite and the bare ice surface. The metabolic states of cells within these microhabitats and in relation to their environment is fundamental to the functioning of the ecosystem and has implications for ecosystem resilience, responses to environmental change, and biogeochemical cycling. This report describes an expedition to Brøggerhalvøya, north-west Svalbard, carried out in July 2025, within the framework of the ERC SIESTA project. A major objective of the project is to resolve microbial activity and dormancy on an individual cell basis, to characterise the adaptive and functional traits of active and dormant fractions of the native glacier microbial population, and to link microbial metabolic states to broader ecological and biogeochemical dynamics. Here we report the site characteristics, the samples collected, the analyses undertaken, and the future analyses planned. Two small valley glaciers near to Ny-Ålesund were selected for investigation during this summer campaign: Midtre Lovénbreen and Austre Brøggerbreen. The data collected in the field, combined with subsequent laboratory analyses, will provide insights into the spectrum of dormancy and activity in situ among glacier microbial communities, and the taxa and functions associated with active and inactive fractions of the communities. These findings will contribute to a deeper understanding of the impacts and role of both short- and long-term microbial dormancy in glacial environments.