Linkages between near-shore hydrodynamics and biological production mediate responses of a large, oligotrophic alpine lake (Issyk-Kul) to climatic drivers (LakeLink)

• Applicants: Professor Dr. Hans-Peter Grossart; Professor Dr. Georgiy Kirillin
• Subject Area: Hydrogeology, Hydrology, Limnology, Urban Water Management, Water Chemistry, Integrated Water Resources Management
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 554994053

LakeLink will evaluate how climate-induced changes in physical processes link with biological productivity in a large, deep oligotrophic alpine lake. Issyk-Kul (Kyrgyzstan) is an important lake ecosystem representing an ideal model site, where biological production in the pelagic zone is low, due to the decoupling of light at the surface and nutrients buried in the sediment. Therefore, biological production is limited to a narrow near-shore area and modulated by complex hydrodynamic processes sensitive to climate-controlled factors. LakeLink aims at establishing quantitative links between physical processes and benthic production at the bottom slope to gain a general mechanistic understanding on responses of large, oligotrophic alpine lakes to climate change. Our core hypothesis states: Benthic communities at the bottom slope make a critical contribution to primary production in deep oligotrophic lakes. Herewith, water-sediment exchange of dissolved and suspended substances driven by physical processes such as internal waves, near-bottom gravity currents, and upwellings are the major suppliers of nutrients and thus regulators of primary and heterotrophic production in this lake type. LakeLink builds upon preliminary joint pilot studies of the German and Kyrgyz teams on Issyk-Kul and is conceived as the first focused research project to be performed on the platform of the newly established German-Kyrgyz field limnological laboratory LILA (Lake Issyk-Kul Environmental Lab) giving start to long-term research on climate-driven changes in deep alpine lake ecosystems of Central Asia. We will perform continuous monitoring of physical and biogeochemical variables (temperature, current velocities, oxygen, and photosynthetically active radiation) in littoral waters and in the upper bottom sediments, covering various temporal scales from inertial and diurnal to seasonal and inter-annual. Regular sampling of littoral water and sediment will quantify nutrient availability as well as activity and diversity of primary producers and heterotrophic bacteria in sediment cores. These in situ measurements will be complemented by lab experiments with natural lake sediments to quantify changes in nutrient and light availability and their effects on benthic net production and organic matter cycling. A 3-dimentional circulation model adapted to Issyk-Kul and a zero-order lake-wide model will be used to perform diagnostic numerical experiments simulating the lake’s physical regime and estimate the biological response to climate changes projected for different regional climate patterns. Quantification of the physical-biological interactions in large, deep lake ecosystems and their potential responses to climate drivers are envisaged as the major outcomes of the project.

• DFG Programme: Research Grants
• International Connection: Kyrgyzstan
• Cooperation Partner: Professor Dr. Salmor Alymkulov
• International Co-Applicant: Professor Dr. Salmor Amanovich Alymkulov