Publication Date:
2020-02-24
Description:
Hule and Rı´o Cuarto are maar lakes located 11 and 18 km N of Poa´s 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 Rı´o 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).
Description:
Published
Description:
e102456
Description:
4V. Vulcani e ambiente
Description:
JCR Journal
Description:
open
Keywords:
bio activity, volcanic lakes, costa rica
;
03. Hydrosphere::03.04. Chemical and biological::03.04.06. Hydrothermal systems
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
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