During the first
part of the 20th century several generations of naturalists investigated subterranean habitats
in order to sample strictly stygobiotic animals. One could call this period, a pre-ecological
phase of groundwater research where the emphasis was more on cataloguing new species,
their habitats and their biogeographical origin. It was the pioneering work of J. SCHWOERBEL
during the 1960s (e.g., SCHWOERBEL, 1961) on the superficial layers of gravel and sands
along rivers and streams, the so-called hyporheic zone, that allowed to obtain a high number
of subsurface animals and to study their phenology. It is this period, which paved the way
for the emergence of modern groundwater ecology. At the same time, ecological aspects of
cave fauna were first studied under experimental conditions in a special cave laboratory in
Southern France (review in ROUCH, 1986)