Physical Limnology of Ponds

• Applicant: Professor Dr. Andreas Lorke
• Subject Area: Hydrogeology, Hydrology, Limnology, Urban Water Management, Water Chemistry, Integrated Water Resources Management
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 558095911

Small lentic (“stagnant”) aquatic ecosystems, often referred to as ponds, make up the majority of the world’s lakes by number. They play a critical role in global biogeochemical cycling and are hotspots of biodiversity. The high microbial activity and biodiversity in ponds are challenged by extreme environmental variability, including significant diel changes in temperature, which can pose severe challenges to the survival of organisms. This thermal dynamics interacts closely with prevailing hydrodynamic conditions, which control the transport of heat as well as of solutes and organisms, and affect their exposure to light and trophic interactions. While flow regimes and thermal stratification have been extensively studied in larger lakes, and reservoirs, surprisingly little is known about the physical conditions in ponds, including the temporal dynamics and spatial variability of temperature and flow velocity, and their dependence on geographic and climatic drivers. Unlike lakes and reservoirs, flows in ponds are expected to be predominantly driven by horizontal density gradients caused by differential heating and cooling. These gradients can arise from partial shading of the ponds, varying water depth, vegetation, and bed properties. This project aims to improve the mechanistic understanding of physical processes in ponds by investigating the spatial and temporal dynamics of water temperature and its role in the generation of density-driven flows and mixing from diel to seasonal time scales. To overcome existing limitations in spatially distributed measurements of temperature and flow velocity in ponds, we will develop specialized low-costs instrumentation. By performing and analyzing unprecedented measurements in ponds and in experimental pond mesocosms, we will develop a mechanistic framework to describe the magnitudes of spatial and temporal variations of temperature and resulting flow velocity as a function of large-scale and site-specific drivers. This framework extends existing approaches for assessing stratification and mixing dynamics in larger lakes by considering convective flows in addition to wind-driven mechanisms. The project is expected to yield novel quantitative insights into the physical processes in pond ecosystems. The derived relationships can support physical habitat characterization in ecological assessments, inform biogeochemical models, and guide the design of constructed ponds.

• DFG Programme: Research Grants