# SIESTA Project: Svalbard summer 2025 expedition report

## TL;DR

This report details a 2025 Svalbard expedition to study how glacier microbes switch between active and dormant states, and how this affects glacier ecosystems and their response to climate change.

## Contribution

The study introduces a direct investigation of microbial activity and dormancy at the single-cell level in natural glacial habitats.

## Key findings

- Microbial dormancy is a key survival strategy in glacier ecosystems.
- The expedition collected samples from two Svalbard glaciers to analyze microbial metabolic states.
- Future analyses will link microbial activity and dormancy to ecological and biogeochemical processes.

## Abstract

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.

Glaciers are cold and harsh environments, but they are not lifeless. Glaciers host diverse microbial communities that survive in surface ice and in small water and debris-filled holes called cryoconite. These microbes drive important processes such as nutrient cycling and carbon transformations. However, because glaciers pose challenging conditions to life, and because conditions can change quickly, many microbes survive by entering a dormant (inactive) state and “waking up” only when conditions improve. Understanding when microbes are active or dormant is crucial for predicting how glacier ecosystems function and how they will respond to climate change. Yet, we still know very little about how common dormancy is on glaciers, which microbes are active or inactive, and what roles they play in the environment. As part of the ERC-funded SIESTA project, we carried out a field expedition in July 2025 to Svalbard, working on two small valley glaciers (Midtre Lovénbreen and Austre Brøggerbreen) near the research town of Ny-Ålesund. Our goal was to investigate microbial activity and dormancy directly in natural microbial habitats on glaciers. We collected samples from different supraglacial environments and used a range of methods to label and identify active and dormant cells at the single cell level. In this report, we describe the study sites, the samples we collected, the analyses we performed in the field, some logistical considerations, and the laboratory work that will follow. The data we generate will reveal how many microbes are active or dormant, which species are involved, and what functions they carry out. This will help us better understand how dormancy shapes glacier ecosystems and influences how they respond to ongoing environmental changes.