The Arctic is changing rapidly due to climate change: sea surface and air temperatures are increasing, the sea ice is thinning and retreating more and more. This has a major impact on the local ecosystem, because: The zone directly under the sea ice is a highly dynamic habitat for a variety of organisms. A research team from the Alfred Wegener Institute has now investigated what these organisms are and how they are affected by the melting ice in the northern Fram Strait. They present their findings in the journal Science of The Total Environment.
The Arctic marginal ice zone (MIZ) is the transition between the pack ice and the open ocean that can extend up to hundreds of kilometers. It is an ecosystem that is significantly influenced by the physical dynamics of the sea ice: multi-year ice is replaced by thinner, first-year ice, the inner edge of the MIZ expands significantly towards the pole and there are more open water areas at the southern edge. In this zone, specialist organisms live inside on the lower surface or directly underneath the ice or in the water. “In our study, we investigated marine biodiversity in the upper water column directly beneath the sea ice in Fram Strait,” says first author Ayla Murray from the Young Investigator Group “ARJEL” at the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI). “And we have identified environmental factors that influence the diversity in the unique habitat under the ice.”
For this, the researchers analyzed seawater samples that they have collected directly under the ice and at depths of up to five meters. The sampled ice stations represent the different ice regimes in the MIZ. From these samples, they extracted environmental DNA (eDNA) and analyzed it using DNA metabarcoding techniques. This is a state-of-the-art method that allows researchers to compare short gene fragments obtained from the samples with genetic reference databases and thus determine which species live in the MIZ. They combined these results with satellite-based environmental data and simultaneous hydrographic measurements on site. “This allowed us to uncover an unexpectedly high level of biodiversity that would have remained largely unknown using traditional survey methods,” says ARJEL group leader Prof. Charlotte Havermans. “In particular, we found that this diversity is greater directly under the sea ice than at a depth of five meters, which underlines the ecological uniqueness of the uppermost water layer.”
The researchers were also able to show that the composition of the eukaryotic communities – that is organisms with cells that have a real nucleus – is strongly influenced by the meltwater stratification, the sea-ice concentration and the proximity to the ice edge. The MIZ thus appears to be the home of unique and specialized communities that could be particularly vulnerable to climate-induced changes. As the marine ecosystems of the Arctic continue to change, it will become increasingly important to monitor changes in biodiversity. “As climate change alters the physical dynamics of this environment, these species face increasing threats,” summarizes Charlotte Havermans. “There is a significant risk that we may lose species unique to ice-associated habitats before we can even identify them. Thus, our study provides critical insights into this fragile ecosystem and underscores the urgent need for further research and conservation efforts.”
Originalpublikation:
Ayla Murray, Simon Ramondenc, Simon F. Reifenberg, Meret Jucker, Mara Neudert, Rebecca McPherson, Wilken-Jon von Appen, Charlotte Havermans. Eukaryotic biodiversity of sub-ice water in the marginal ice zone of the European Arctic: A multi-marker eDNA metabarcoding survey. Science of The Total Environment. 2025. https://doi.org/10.1016/j.scitotenv.2025.178840.