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Ecological evaluation of aquatic and terrestrial subterranean fauna in a karst cavePeter Kozel, 2018, doctoral dissertation
Abstract: Studies on environmental parameters−subterranean fauna relationship and spatial and temporal patterns of subterranean fauna have dealt with either aquatic or terrestrial faunas. So far, no simultaneous ecological evaluation of aquatic and terrestrial faunas has been performed. To address this issue, we conducted a pilot study dealing in parallel with these two faunas in the cave Zguba jama near Postojna, Slovenia, applying monthly sampling over one year. Aquatic fauna was sampled from permanent water drips, and terrestrial fauna by visual inspection and advanced baited pitfall trapping, along with recording the main abiotic parameters. In percolating water, we recorded aquatic fauna, Copepoda being the dominant taxon, and species-rich troglobiotic fauna, which most probably coexist with aquatic species in a semi-aquatic epikarst environment. Analyses revealed that temperature, distance from the entrance and ceiling thickness are the most important parameters that influence the presence of stygobionts; higher values of these parameters result in a higher probability of the presence of stygobionts in percolation water. The recorded spatial distribution of stygobionts varied distinctly among the sampling sites. This indicates that fauna in sampled drips originated from aquatic or semiaquatic epikarst microhabitats, being completely or nearly completely separated from each other, and probably varied according to environmental characteristics. The temporal pattern of the stygobiotic fauna dynamics presumably occurred because of variable water flow rates and the specific physical and chemical characteristics of the water. The abundance of troglobionts showed distinctive spatial distribution pattern over the seasons. In spring and summer, the highest abundances and the highest probability of presence were found near the entrance. In autumn and winter, unfavorable conditions in the entrance zone most likely triggered the migration of troglobionts towards the climatically more stable deep cave zone, and from the cave into the adjacent fissure network. The highest abundance of troglobionts was found at 7–9°C and relatively high ground substrate moisture. Additionally, we found a higher probability of the presence of troglobionts in cave sections with a larger passage cross-section size, which is probably due to the greater variability of microhabitat types in spacious cave sections. In addition, the higher probability of presence relates to higher substrate pH. One potential explanation for this could be that the specific microorganism communities present in such conditions support the nutritional needs of troglobionts. Most troglobiotic species preferred the deep cave zone where the highest species richness and diversity were also observed. Species richness, abundance and diversity of troglophiles and trogloxenes were highest in the entrance zone and showed relatively similar patterns within the cave. However, troglophiles were more abundant in the transition zone and the initial part of the inner zone. The temporal pattern of trogloxenes and presumably of most troglophiles occurred because of migration between the surface and the cave. The probability of the presence of trogloxenes was highest in the entrance zone and in winter, owing to massive overwintering in the cave. A modified technique of pitfall trapping by placing traps in two parallel sets, a ground and an upper one along the cave, resulted in recording greater species diversity in comparison with the traditional method, i.e., ground pitfall trapping alone. It turned out that such sampling contributes at the same time to both more effective and less invasive inventory of subterranean fauna. The dynamics of relative abundance and species richness of stygobionts and troglobionts within the cave showed partly comparable annual patterns. Nevertheless, our findings point toward the need for a long-term and more detailed study in future to address this question properly.
Keywords: biological inventories, epikarst fauna, faunal dynamics, microhabitats, stygobionts, troglobionts, troglophiles, trogloxenes, Zguba jama
Published in RUNG: 16.02.2018; Views: 4540; Downloads: 315
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