Organic geochemistry and mineralogy suggest anthropogenic impact in speleothem chemistry from volcanic show caves of the Galapagos
Ana Z. Miller,
Nicasio T. Jiménez-Morillo,
Mathilda L. Coutinho,
Fernando Gazquez,
Vera Palma,
Francesco Sauro,
Manuel F.C. Pereira,
Fernando Rull,
Theofilos Toulkeridis,
Ana T. Caldeira,
Paolo Forti,
José M. Calaforra
Affiliations
Ana Z. Miller
Instituto de Recursos Naturales y Agrobiologia de Sevilla (IRNAS-CSIC), Seville, Spain; HERCULES Laboratory, University of Évora, Évora, Portugal; Corresponding author
Nicasio T. Jiménez-Morillo
MED—Mediterranean Institute for Agriculture, Environment and Development, University of Évora, Évora, Portugal
Mathilda L. Coutinho
HERCULES Laboratory, University of Évora, Évora, Portugal
Fernando Gazquez
Department of Biology and Geology, University of Almería, Almería, Spain; Andalusian Centre for the Monitoring and Assessment of Global Change (CAESCG), University of Almería, Almería, Spain
Vera Palma
HERCULES Laboratory, University of Évora, Évora, Portugal
Francesco Sauro
Department of Earth Sciences and Environmental Geology, University of Bologna, Bologna, Italy
Manuel F.C. Pereira
CERENA, Instituto Superior Técnico, University of Lisbon, Lisbon, Portugal
Fernando Rull
CSIC-CAB Associated Unit ERICA, Department of Condensed Matter Physics, Mineralogy and Crystallography, University of Valladolid, Boecillo, Spain
Theofilos Toulkeridis
Universidad de las Fuerzas Armadas (ESPE), Campus Sangolquí, Sangolquí, Ecuador
Ana T. Caldeira
HERCULES Laboratory, University of Évora, Évora, Portugal
Paolo Forti
Department of Earth Sciences and Environmental Geology, University of Bologna, Bologna, Italy
José M. Calaforra
Department of Biology and Geology, University of Almería, Almería, Spain; Andalusian Centre for the Monitoring and Assessment of Global Change (CAESCG), University of Almería, Almería, Spain
Summary: The network of lava tubes is one of the most unexploited natural wonders of the Galapagos Islands. Here, we provide the first morphological, mineralogical, and biogeochemical assessment of speleothems from volcanic caves of the Galapagos to understand their structure, composition, and origin, as well as to identify organic molecules preserved in speleothems. Mineralogical analyses revealed that moonmilk and coralloid speleothems from Bellavista and Royal Palm Caves were composed of calcite, opal-A, and minor amounts of clay minerals. Extracellular polymeric substances, fossilized bacteria, silica microspheres, and cell imprints on siliceous minerals evidenced microbe-mineral interactions and biologically-mediated silica precipitation. Alternating depositional layers between siliceous and carbonate minerals and the detection of biomarkers of surface vegetation and anthropogenic stressors indicated environmental and anthropogenic changes (agriculture, human waste, and cave visits) on these unique underground resources. Stable isotope analysis and Py-GC/MS were key to robustly identify biomarkers, allowing for implementation of future protection policies.
