Lay summary
Lake Ohrid, located between Macedonia and Albania, is the only ancient, long-lived lake in Europe representing a global hotspot of biodiversity with more than 200 endemic species. More than half of its water input is from karst springs, which supply the lake subaquatically with cool and oxygen-rich water. Several endemic organisms are found exclusively close to the springs, indicating that their water may have been important for the evolution of the unique aquatic ecosystem of Lake Ohrid.

Particularly the subaquatic springs seem to have a large potential as specific habitats for endemic species. Despite their unique role, very little is known about the underwater springs. Thus the first goal of the project is to achieve an inventory of these subaquatic springs (discharge, depth, location, size, etc). Once they are located, differences of the physical and geochemical properties of the water can be determined and the different species composition can be analysed. Temperatures as well as major ions are measured for all sources and in addition, at selected sites temperature and conductivity will be recorded continuously in order to estimate the long-term stability. Biological samples will be collected by divers (shallower locations) and with grab-sampler (deeper sites) and subsequently analysed under the microscope. For selected samples, genetic analysis will be performed.

The biological survey will resolve whether the subaquatic spring sites are indeed major hosts for verified or even unknown endemic species. Knowledge of the spring properties will potentially enable the assessment on how the springs could or already do react to human impacts, such as water abstraction, pollution or climate change.

The results of the proposed project will provide a valuable status quo of the subaquatic spring characteristics and a reference point for future studies. If indeed the springs are found to be important habitats for endemic species, a follow-up project is envisaged, regarding the genetic distinction of these species for assessing the evolutionary role of the spring areas. Finally, lake management consequences will be formulated in discussion with experts and representatives of the local Ministry of Environment.