In the underground, water is found in larger or smaller spaces (caves, pits, caverns, cracks), and it emerges from the aquifers through springs. Groundwater is a habitat of stygobionts (aquatic cave species), who are generaly explored by entering underground spaces (caves, pits and springs). In the Plitvice Lakes National Park, over 230 caves and pits are known to cavers, but none of them reach underground water flows. Also, many springs are known in the Park, but all of them are seepage springs, so it is not possible to enter them. As the consequence of all that, not many data on Plitvice Lakes stygobionts were avaliable.
For the aforementioned reasons the project „eDNA of aquatic ecosystems“ was started, during which environmental DNA (eDNA) method was used for the research of stygobionts. It is possible to obtain fauna composition by samplnig water (which contains DNA), maybe even to find new species in cave aquatic systems. Special attention was paid on search for the olm (Proteus anguinus), Natura 2000 target species which was known near the Park, but not in the Park.