Beneath the surface: Climatic, Micro-climatic, Geochemical and Microbiological Approach to Karstic Cave Ecosystem

As semi-closed ecosystems, biotic and abiotic properties of cave environments are extensively isolated from the impacts of the surface processes, except for a few environmental parameters. Surface climatic parameters (atmospheric CO₂ ratio, temperature, and precipitation amount) and vegetation are known with their impact on the environmental parameters such as the CO₂ partial pressure, temperature, and humidity of the cave atmosphere. These properties of cave microclimate are defined over a long-term process of balancing all the input and output heat and mass fluxes under the influence of soil temperature, seepage water content and the chemical/physical properties of sinking streams as well as direct air flux from the outside into the cave. While this interaction between the surface and in-cave environmental parameters exerts a key factor on the hydro/geochemical, and microbiological properties of the cave by altering the biotic and abiotic conditions, cave environments can be considered as long-term archives of the consequences of this interaction by being highly sheltered to the surface processes. This relationship between sediment geochemistry, microbiology and environmental conditions is still not fully understood.

In this study, the relationship between bacterial diversity, sediment geochemistry, and microclimate as three major components of cave ecosystems will be examined in cave environments, the relationship between in-cave and surface atmospheric conditions as well. In order to determine the in-cave environmental conditions, micro-climatic (CO₂, temperature, humidity) and environmental (cave water pH, alkalinity) parameters were measured during the fieldwork. Sediment and water (drip water, underground river water and pond water) were sampled in two seasons (summer and winter) aseptically as triplet to determine bacterial community composition of these caves. Water, sediment, and speleothem samples from the caves were examined by Inductively Coupled Plasma - Mass Spectrometry (ICP-MS) and Next Generation Sequencing (NGS) methods to reveal the geochemical and metagenomic features. To observe the changes in cave micro-climate for a year-long period, dataloggers were used.