Gourgouthakas 2022: report of the cave expedition of LOC1, Crete, Greece

Gourgouthakas cave (LOC1 code name) is located at an altitude of 1550m, in the area of Atzines or Atzinolakas, on the northern side of Lefka Ori (White Mountains) of Crete, Greece. It is among the two deepest caves in Greece and the 50 deepest in the world, reaching a depth of 1100m. Gourgouthakas cave was found during the French caving expedition “Lefka Ori 1981” of the Speleological Society of Plantaurel (SSP) and its explorations began in the 1990s by the Speleo Group Catamaran. The cave was explored and mapped to its current depth during an international expedition that was held in 1998, while the last expedition was held in 2001. Herein, the “Gourgouthakas 2022” expedition, a joined effort from 40 speleologists from 12 speleological clubs of Greece, which took place 21 years since the last one (SELAS-SPOK expedition, 2001), is reported. Through this expedition we aimed at mapping the cave with advanced contemporary tools to create a more detailed mapping, scuba cave diving at the first siphon at the depth of 678m, scientific sampling for geological and biological research and gathering the speleological community of Greece. The expedition was held in two phases. During the first phase (9 days), the speleologists set the basecamp, rigged the cave with new materials until the second bivouac at -649m, and installed the telecommunications in the cave. At the second phase (16 days), the cave was rigged, photographed, mapped and lithostratigraphically studied until the second siphon at the depth of 1100m. Macroinvertebrates and microbes were sampled from 7 and 9 different stations respectively, while water samples were collected from 5 different stations for eDNA metagenome analysis. Several faults were recorded from the entrance to the deepest part of the cave with the stratigraphic column constituted, from top to bottom, by Triassic to Jurassic Trypali unit with mainly recrystallized marble (entrance to -522m), Plattenkalk unit with a thin layer of Oligocene metaflysch (-522m to -850m), partly marbled limestone (-850m to -900m) and Plattenkalk unit with several siliceous concretions (-900m to -1100m). In total, 52 macroinvertebrate individuals belonging to more than 7 different troglobiont taxa were sampled, with a new species of niphargid amphipod being described, while more than 200 stains of microbes were cultivated from the scraped collected samples. This expedition provided the opportunity to many speleologists to experience the acclimatization and d