Geochemical characterization of clastic sediments sheds light on energy sources and on alleged anthropogenic impacts in cave ecosystems

Rosangela Addesso,Simona Cafaro,Jo De Waele,Daniela Baldantoni

doi:10.1007/s00531-021-02158-x

Rosangela Addesso, Simona Cafaro + Show 2 more

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https://doi.org/10.1007/s00531-021-02158-x

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Journal: Geologische Rundschau	Publication Date: Jan 10, 2022
Citations: 5	License type: open-access

Affiliation: University of Salerno, University of Bologna

Abstract

Caves are usually oligotrophic ecosystems, where the organic matter represents a limiting factor to the hypogeal community and sediments are often a significant energy source. With a view to identifying the energy input influencing the ecological processes occurring in caves, as well as the potential alteration sources of the natural equilibriums, geochemical features of several typologies of clastic sediments from the Pertosa-Auletta Cave (Italy) were investigated. The collected sediments, analyzed for a number of chemical (organic matter, Al, B, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Li, Mg, Mn, Mo, Na, Ni, P, Pb, S, Si, Sr, Ti, V, Zn concentrations) and mineralogical (quartz, calcite, dolomite, clay minerals) characteristics, showed a different composition. Overall, their origin is supposed to be allochthonous, related to the important fluviokarst activities interesting the cave in the past, whereas the abundance of calcitic and dolomitic compounds can be autochthonous, being the carbonate the main host rock. The highest concentrations of organic matter, together with C, Cu, Mo, N, P, Pb, S and Zn, highlighted in one sample composed mainly of bats guano, revealed an important bioavailable energy input as well as a pollutant accumulation, mainly of anthropogenic origin.

Highlights

Sediments represent a significant energy source in caves, being these ecosystems generally poor in nutrients, mainly due to the absence of organic matter deriving from the photoautotrophic primary producers, limited only to the lighted entrance areas (Gillieson 1996; Mammola and Isaia 2018) or to the lit trails of tourist caves (Mulec and Kosi 2009)
The goal of this study was to investigate the geochemical nature of clastic sediments collected in the Pertosa-Auletta Cave (Campania Region, southern Italy), which represents an excellent model of a heterogeneous cave system (Addesso et al 2019, 2021)
6 samples were taken from the tourist trail (Ts), 5 from the fossil trail (Fs) and 5 from the active trail (As), collecting them from accumulations found on rock recesses or those deposited on the floor, left there by intense water currents when the cave passages were still active

Summary

Introduction

Sediments represent a significant energy source in caves, being these ecosystems generally poor in nutrients, mainly due to the absence of organic matter deriving from the photoautotrophic primary producers, limited only to the lighted entrance areas (Gillieson 1996; Mammola and Isaia 2018) or to the lit trails of tourist caves (Mulec and Kosi 2009). External pollutants from surface anthropogenic activities or visitors in show caves may represent further energy sources altering the natural nutrient-poor ecological equilibrium of underground ecosystems (Chelius et al 2009; Dredge et al 2013; Smith et al 2013). Allochthonous particles, such as dust, fibers, hair, and bacteria, spores and seeds can constitute organic and inorganic inputs emanated in the cave (Russell and MacLean 2008) and depositing on the floor and wall surfaces. Throughout an extensive geochemical sediment characterization, from pristine to disturbed states, this research aims to shed light on the energy sources in caves, helping to identify potential anthropogenic impacts in the karst ecosystem

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