The Arctic Ocean plays a key role in regulating the global climate and is highly sensitive to climate change. Temperatures have increased more strongly at the poles than the global average during the recent and the year 2018 marked the sixth lowest sea-ice minimum in the nearly 40-year satellite record. Loosing sea-ice triggers a combination of feedback processes known as a “Arctic Amplification” phenomenon. For example, when sea ice melts in the summer, it opens up dark areas of water that absorb more heat from the sun, which in turn melts more ice. This “feedback loop” also includes the effects of melting snow and thawing permafrost. The loss of sea ice changes the light environment, available nutrients and consequently food web processes and the microbial loop.

The effect of the Arctic Amplification is also most pronounced in winter, however, there is hardly any data available for the Polar Night season because of the logistical challenges involved navigating sea ice covered areas. But winter data is needed to establish year-around baselines and to understand seasonal cycles.

Our team investigates the impact short-term (e.g. seasonal) and long-term (e.g. climate-driven) changes in the physical environment have on pelagic microbial ecosystems and develop a quantified understanding of the structure and functioning of Arctic ecosystems.

Since 2009, we conduct annual spring/summer cruises to the AWI Hausgarten in Fram Strait as part of PEBCAO group (Plankton Ecology and Biogeochemistry in a Changing Arctic Ocean) to characterize changes in organic matter cycling and to track major changes in autotrophic and heterotrophic production. We investigate the production of dissolved organic matter (e.g. the release of carbon fixed via photosynthesis) and evaluate its quality by determining concentrations of amino acids and carbohydrates available for the consumption by bacteria. Additionally, bacterial production is investigated and we assess the importance of micro gels as bacterial habitats.

The µARC project expands those efforts in a larger collaborative effort to fully characterize the microbial base (archaea, bacteria, protists including phytoplankton and fungi) of the pelagic Arctic food web in relation to organic matter cycling. We have the unique opportunity to participate in the MOSAiC  field campaign to obtain samples from the Central Arctic Ocean in rarely samples winter and early spring months, which will allow us to quantify impacts of Arctic seasonality on the structure and functioning of microbial ecosystems in relation to organic matter cycling.