Biological Enhancement of Speleogenesis in Carbonate Karst Systems

Buchanan 2022

Abstract

Subterranean biological communities play a critical role in enhancing speleogenesis in natural carbonate karst systems. Through the production of carbonic and sulfuric acids, organic acid secretion, and physical interactions with the substrate, organisms such as microbes, amphipods, and other stygofauna contribute to the chemical and mechanical dissolution of carbonate rock. This paper explores these processes from a molecular and ecological perspective, providing a cited and structured understanding of how biology drives geological transformation underground.

1. Introduction

Speleogenesis, the formation and development of caves, has traditionally been considered a primarily geochemical process driven by the dissolution of carbonate rocks. However, recent studies underscore the role of biological processes in accelerating and shaping cave formation (Banks, Burke and Smith, 2010). This biogenic speleogenesis occurs in environments where microbial metabolism, organic matter decomposition, and faunal activity contribute to the geochemical environment. In particular, subterranean ecosystems in karst environments offer a dynamic interplay between biology and geology that enhances cave development.

2. CO₂ and Acid Generation

Subterranean fauna and microbes respire and produce carbon dioxide (CO₂), which reacts with water to form carbonic acid (H₂CO₃):

CO2+H2O→H2CO3 ​

This acid dissociates into bicarbonate (HCO₃⁻) and hydrogen ions (H⁺), promoting limestone dissolution:

CaCO3+H2CO3→Ca2++2HCO3

Such reactions drive karstification and enhance porosity in carbonate systems (Ford and Williams, 2007).

3. Sulfuric Acid Speleogenesis (SAS)

In hypogenic environments, sulphur-oxidizing bacteria metabolise hydrogen sulphide (H₂S) into sulfuric acid (H₂SO₄):

H2S+2O2→H2SO4

This stronger acid aggressively dissolves limestone, a mechanism observed in cave systems like Carlsbad Caverns and Cueva de Villa Luz (Engel, Stern and Bennett, 2004).

4. Microbial Biofilms and Organic Acids

Microbes colonise cave walls in biofilms, concentrating acidic byproducts such as acetic and citric acid, which locally reduce pH and intensify dissolution (Northup and Lavoie, 2001). This leads to microscale pitting, etching, and ultimately larger void formation, particularly under oligotrophic conditions where nutrient cycles are tightly regulated.

5. Bioturbation and Physical Alteration

Stygofauna like amphipods, isopods, and worms disturb sediments and promote water circulation, a process known as bioturbation. This facilitates microbial colonisation, enhances nutrient availability, and increases rock surface exposure to acidic conditions (Gibert and Deharveng, 2002). Such activities mechanically aid in opening fissures and extending cave systems.

6. Synergistic Biospeleogenesis

Biogenic speleogenesis is a result of synergistic feedback loops: biological CO₂ and acid production promotes dissolution, creating voids that are further colonised and expanded by living organisms. This cycle leads to long-term cave evolution that is both chemically and biologically mediated (Barton and Northup, 2007).

7. Conceptual Diagram

The conceptual diagram below illustrates the interactions between subterranean life and cave formation processes, including CO₂ respiration, acid generation, microbial etching, and faunal bioturbation:

 

8. Conclusion

The role of biological communities in speleogenesis is increasingly recognised as a crucial driver in carbonate karst systems. From microbial acid production to physical sediment manipulation by stygofauna, these interactions enhance cave formation and expand our understanding of subterranean ecosystem functions. Future research and conservation strategies must account for these biogenic contributions when assessing karst hydrology and ecosystem services.

 

References

Banks, E., Burke, G. and Smith, B. (2010) ‘Microbial effects on karst dissolution’, Geomicrobiology Journal, 27(4), pp. 274–288.

Barton, H.A. and Northup, D.E. (2007) ‘Geomicrobiology in cave environments: past, current and future perspectives’, Journal of Cave and Karst Studies, 69(1), pp. 163–178.

Engel, A.S., Stern, L.A. and Bennett, P.C. (2004) ‘Microbial contributions to cave formation: new insights into sulfuric acid speleogenesis’, Geology, 32(5), pp. 369–372.

Ford, D. and Williams, P. (2007) Karst Hydrogeology and Geomorphology. Chichester: Wiley.

Gibert, J. and Deharveng, L. (2002) ‘Subterranean ecosystems: a truncated functional biodiversity’, Bioscience, 52(6), pp. 473–481.

Northup, D.E. and Lavoie, K.H. (2001) ‘Geomicrobiology of caves: a review’, Geomicrobiology Journal, 18(3), pp. 199–222.

 

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