Hule and Río Cuarto are maar lakes located 11 and 18 km N of Poás volcano along a 27 km long fracture zone, in the Central Volcanic Range of Costa Rica. Both lakes are characterized by a stable thermic and chemical stratification and recently they were affected by fish killing events likely related to the uprising of deep anoxic waters to the surface caused by rollover phenomena. The vertical profiles of temperature, pH, redox potential, chemical and isotopic compositions of water and dissolved gases, as well as prokaryotic diversity estimated by DNA fingerprinting and massive 16S rRNA pyrosequencing along the water column of the two lakes, have highlighted that different bio-geochemical processes occur in these meromictic lakes. Although the two lakes host different bacterial and archaeal phylogenetic groups, water and gas chemistry in both lakes is controlled by the same prokaryotic functions, especially regarding the CO2-CH4 cycle. Addition of hydrothermal CO2 through the bottom of the lakes plays a fundamental priming role in developing a stable water stratification and fuelling anoxic bacterial and archaeal populations. Methanogens and methane oxidizers as well as autotrophic and heterotrophic aerobic bacteria responsible of organic carbon recycling resulted to be stratified with depth and strictly related to the chemical-physical conditions and availability of free oxygen, affecting both the CO2 and CH4 chemical concentrations and their isotopic compositions along the water column. Hule and Río Cuarto lakes were demonstrated to contain a CO2 (CH4, N2)-rich gas reservoir mainly controlled by the interactions occurring between geosphere and biosphere. Thus, we introduced the term of bio-activity volcanic lakes to distinguish these lakes, which have analogues worldwide (e.g. Kivu: D.R.C.-Rwanda; Albano, Monticchio and Averno: Italy; Pavin: France) from volcanic lakes only characterized by geogenic CO2 reservoir such as Nyos and Monoun (Cameroon).
Dipartimento di Scienze della Terra, University of Florence, Florence, Italy;Dipartimento di Scienze della Terra, University of Florence, Florence, Italy;CNR – Istituto di Geoscienze e Georisorse, Florence, Italy;Department of Food, Environmental and Nutritional Sciences, University of Milan, Milan, Italy;Department of Food, Environmental and Nutritional Sciences, University of Milan, Milan, Italy;Dipartimento di Scienze della Terra e del Mare, University of Palermo, Palermo, Italy;Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Bologna, Bologna, Italy;Istituto Nazionale di Geofisica e Vulcanologia, Osservatorio Vesuviano, Naples, Italy;Department of Food, Environmental and Nutritional Sciences, University of Milan, Milan, Italy;Department of Food, Environmental and Nutritional Sciences, University of Milan, Milan, Italy;Istituto Nazionale di Geofisica e Vulcanologia, Osservatorio Vesuviano, Naples, Italy;Dipartimento di Scienze della Terra, University of Florence, Florence, Italy;CNR – Istituto di Geoscienze e Georisorse, Florence, Italy;Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Palermo, Palermo, Italy;Dipartimento di Scienze della Terra, University of Florence, Florence, Italy;CNR – Istituto di Geoscienze e Georisorse, Florence, Italy;Dipartimento di Scienze della Terra, University of Florence, Florence, Italy;Istituto Nazionale di Geofisica e Vulcanologia, Osservatorio Vesuviano, Naples, Italy;Centro de Investigaciones en Ciencias Geológicas, Escuela Centroamericana de Geología, Red Sismológica Nacional, Universidad de Costa Rica, San Jose, Costa Rica;Centro de Investigaciones en Ciencias Geológicas, Escuela Centroamericana de Geología, Red Sismológica Nacional, Universidad de Costa Rica, San Jose, Costa Rica
Recommended Citation:
Jacopo Cabassi,Franco Tassi,Francesca Mapelli,et al. Geosphere-Biosphere Interactions in Bio-Activity Volcanic Lakes: Evidences from Hule and Rìo Cuarto (Costa Rica)[J]. PLOS ONE,2014-01-01,9(7)