The Fascinating Biology of Stinky Caves – Sulfidic subterranean Biology
Given by Dr. Serban Sarbu, Institute of Speleology Emil Racovita on 05.11.2024
Over hundreds of years, caves in general have been considered as dark places, where no photosynthesis and hence production can be performed. Today it is known, that chemolithoautotrophic microbes that can be found in the deep sea, also occur in sulfidic caves. These microorganisms function as the base of further evolved and complex food webs of a diverse and dense fauna, which is highly adapted to the life in dark and anoxic conditions. Serban Sarbu and his research team studied these communities in several sulfidic caves in Europe and Western Asia.
In general, sulfidic caves have a redox interface, which is inhabited by microorganisms. The redox interface allows microorganisms to produce food by using oxygen to oxidise hydrogen sulphide. This interface can occur between gas and water, gas and gas or in marine caves fed by sulfidic freshwater even between water and water.
By exploring the Movile Cave, Romania Sarbu found a floating microbial biofilm on the cave lakes surface and 37 endemic invertebrate species. Most of them are, in adaption to the environmental conditions, blind and unpigmented. Furthermore, by analysing the stable isotope ratio of C13 and N15 of the invertebrates, it could be shown that samples from the cave where isotopically lighter than samples from outside the cave. This suggests that the organisms in the cave are not connected to food webs of photosynthetic origin from outside the cave.
Surprisingly, in Sulfur Cave in the Vromoner Canyon, Greek, the in Europe common surface species Tegenaria domestica could be found in a colony of about 70,000 individuals. This colony of spiders is mostly fed by the chironomid flies. Whereas in the other part of the cave a food web based on collembola feeding from the biofilm could be found. These collembola for their part are the food source of endemic scorpions.
Overall, further research is planned to gain a better understanding of the complex and highly specialized food webs in sulfidic caves, as they are a key in understanding evolutionary processes and preserving a unique biodiversity.