The Arctic Ocean plays a key role in regulating the global climate and is highly sensitive to climate change. In the last 40 years temperatures have increased four times faster at the poles than the global average. At present, Arctic regions are undergoing rapid and complex environmental changes, such as an increased advection of warm waters and a decrease in sea-ice extent and thickness.
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. Yet, winter data is needed to establish year-around baselines and to understand seasonal cycles. We had the unique opportunity to participate in the MOSAiC (Multidisciplinary drifting Observatory for the Study of Arctic Climate) field campaign to obtain samples from the Central Arctic Ocean in rarely sampled winter and early spring months, which allow us to quantify impacts of Arctic seasonality on the structure and functioning of microbial ecosystems in relation to organic matter cycling. Additionally, during the Arctic Century expedition, we used a multidisciplinary approach to study the rarely accessible and remote areas in the Kara and Laptev Sea as well as on Franz Josef Land and Severnaya Zemlya in the western Arctic.
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 to understand how planktonic microbes regulate organic matter biogeochemical cycling and establish how these processes vary throughout the seasonal cycle.
Our team investigates both the impact of short-term (e.g. seasonal) as well as long-term (e.g. climate-driven) changes in the physical environment have on pelagic microbial ecosystems driven by increased inflow of warm and saline Atlantic waters into the Arctic – a phaenomenon called “Atlantification”.
Both Atlantification and sea ice loss are expected to impact phytoplankton dynamics. As organic matter produced by phytoplankton forms the basis of the marine food web these changes might also affect organic matter pool size and composition and as a consequence the biological carbon pump. However, these dynamics are still not well understood.
Since 2009, we conduct annual spring/summer cruises to the LTER Observatory HAUSGARTEN in Fram Strait as part of PEBCAO (Plankton Ecology and Biogeochemistry in a Changing Arctic Ocean) group 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.
Based on our time series data the INDIFUN-AI project aims to develop an early warning system for changes in marine planktonic biodiversity. Therefore, biochemical indicators for functional changes in primary producers will be assessed by laboratory incubation experiments and the analysis of the long term HAUSGARTEN dataset by using the latest AI-supported statistical method.
Within the ICEBERG (Innovative Community Engagement for Building Effective Resilience and Arctic Ocean Pollution-control Governance) project, the focus lies on a different aspect of global change: The effect of anthropogenic pollution in the form of microplastics on the microbial community and biogeochemistry. By analysing the biodiversity and function of plastic-associated bacteria using 16S amplicon sequencing and metatranscriptomics, we seek to understand potential pathogens and their resistance mechanisms against antibiotics, and thereby the potential risks of microplastics to human and ecosystem health.
