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New insights into the volcanic unrest at Campi Flegrei (southern Italy) based on an integrated geochemical and microbiological investigation at Astroni lakes.

F. Tassi ^1,2,3^; A. Randazzo3, S. Venturi1,2, A. Repetto1, S. Fazi4,5, S. Amalfitano4,5, L. Vimercati6; A. Butturini7, S. Caliro8, E. Cuoco8, A. Santi8, F. Capecchiacci1,8, J. Cabassi2, F. Canonico9, G. La Magna9, R. Isaia8

  • Affiliations:  1Department of Earth Sciences, University of Florence, Via G. La Pira, 4, 50121, Florence, Italy 2Institute of Geosciences and Earth Resources, National Research Council (CNR-IGG) Via La Pira 4, 50121 Florence, Italy 3Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Roma 1, Via di Vigna Murata, 605 - 00143 Roma, Italy 4Water Research Institute, National Research Council (IRSA-CNR), Via Salaria km 29.300, 00010 Montelibretti, Roma, Italy 5 National Biodiversity Future Center (NBFC), Piazza Marina 61, 90133 Palermo, Italy 6University of Colorado at Boulder, Department of Ecology and Evolutionary Biology, 80309 Boulder, CO, USA 7Department of Evolutionary Biology, Ecology and Environmental Sciences, University of Barcelona, Barcelona, Spain 8Istituto Nazionale di Geofisica e Vulcanologia, Osservatorio Vesuviano, via Diocleziano 328, 80124 Naples, Italy 9Fondazione WWF Italia - Riserva Naturale dello Stato Oasi WWF Cratere degli Astroni, Via Agnano agli Astroni 468, 80124 Napoli 

  • Presentation type: Poster

  • Presentation time: Friday 16:30 - 18:00, Room Poster Hall

  • Poster Board Number: 84

  • Programme No: 6.8.10

  • Theme 6 > Session 8

Abstract

Astroni is a 2×1 km wide crater in the Campi Flegrei caldera (southern Italy) hosting three small lakes, namely Lago Grande (LG), Cofaniello Grande (CG), and Cofaniello Piccolo (CP), presenting a varied ecosystem rich in reeds, bulrushes and willows. In this study, possible relationships between the lakes and the hydrothermal fluid circulation system were investigated based on geochemical data of the lakes and microbiological analyses of lake waters and sediments. Lake chemistry, showing a Na+-HCO3- facies and relatively high TDS values (up to 1,820 mg/L), was consistent to that typically found in discharges located at the periphery of upflow zones of active hydrothermal-volcanic systems. LG was characterized by an anoxic hypolimnion with relevant concentrations of biogenic CH4 and a mixture of biogenic and hydrothermal CO2. The dependence of the chemistry of the Astroni lakes on inputs from the Campi Flegrei hydrothermal system may explain the anomalous increase of the LG water level recorded in the last years, which was not consistent with the temporal pattern of rainfall in that area and never observed before. The increasing hydraulic pressure related to the enhanced hydrothermal steam condensation recorded in the last decades can indeed have caused the observed change in the LG water volume. The increase of the LG water level, besides acting as an indicator for the volcanic crisis, may have a strong environmental impact, since it affects the terrestrial and aquatic compartments of the Astroni crater, with direct consequences on the unique ecosystem functioning of the lakes.