Rapid shift in microbial community structure in a neutral hydrothermal hot spring from Costa Rica

In this work, we characterize the geochemistry and microbial community of Bajo las Peñas, a neutral (pH 6.5-7.4), hot spring (T = 62.0-68.0°C) located near Turrialba Volcano, Costa Rica. The microbiota at its two sources belongs mainly to the family Aquificae, comprising OTUs closely related to the genera Sulfurihydrogenibium, Thermosulfidibacter, Thermodesulfovibrio and Thermocrinis which is consistent with the presence of moderate levels of sulfate (243-284 mg/L) along the stream. We determined a dramatic shift in the microbial community just a few meters downstream of the sources of the hot spring (15-20 meters), with a change from sulfur related chemoautotrophic (e.g. Sulfurihydrogenibium and an OTU closely related to Thermodesulfovibrio) to chemoheterotrophic prokaryotes (e.g. Meiothermus, Nitrososphaera, Thermoflexus, Thermus). Thus, in this neutral hot spring, the first level of the trophic chain is associated with photosynthesis as well other anaerobic CO2 fixing bacteria. Then, thermotolerant chemoheterotrophic bacteria colonize the environment to degrade organic matter and use fermentative products from the first level of the trophic chain. Our data demonstrate how quickly the microbial community of an ecosystem can change in response to environmental variables and sheds light on the microbial ecology of less common circumneutral pH hot springs.

STUDYING EVOLUTION OF HYDROTHERMAL ALTERATION MATERIALS IN THE TURRIALBA VOLCANO TROUGH MULTISPECTRAL AND HYPERSPECTRAL IMAGES

The aim of this work is to develop a geospatial methodology for the analysis of the time evolution of The Turrialba volcano using different automatic imaging techniques compared to expert-based remote sensing techniques. Change detection of hydrothermal alteration materials in relation with time series from multisensor data acquired in spectral ranges of the visible (VIS) and short wave infrared (SWIR) have been calculated. We used for this purpose multispectral and hyperspectral scenes of the Sentinel 2, ALI and Hyperion sensors, respectively, on four dates from 2013 and 2018. This work adopts a multi-source approach, applied to the analysis of the correlations between hydrothermal materials and spectral anomalies in The Turrialba volcano complex, located in The Central Volcanic Range (Costa Rica).An expert-based technique called Crosta’s technique for detecting hydrothermal materials have been applied. We have chosen four variables for generating a different Principal Component Analysis (PCA) for groups of channels, two highly reflective and two highly absorptive for each mineral. We have tested another technique to detect hydrothermal materials based on a discrete spectral profile analysis and an unsupervised data mining approach. In other sense, we have applied an automatic technique called anomaly detection to compare with the hydrothermal materials results. Results are presented as an approach based on a comparison of two different strategies whose main future interest lies in the automated identification of patterns of hydrothermally altered materials without prior knowledge or poor information about the area, which has relevant implications in image-based prospecting.

Cortical deformation in the Aguacaliente-Navarro fault system (Central Valley, Costa Rica) from Geodetic data (GNSS and InSAR)

<p>The Central Valley, Costa Rica, is subject to moderate seismicity, related to the Central Costa Rica Deformation Belt: a region with diffuse deformation, where Caribbean, Cocos and Nazca Plates, as well as the Panama Micro-plate, interact.  The Eastern part of the valley is dominated by the Aguacaliente-Navarro fault system. The city of Cartago was destroyed by an earthquake Ms 6.4 in 1910, associated with the rupture of the Aguacaliente fault. Volcanic unrest –mainly in Turrialba Volcano, with recent activity reported- is present in the area, thus resulting in a very complex interaction zone, where seismic hazard studies are crucial.</p><p>In this context, we process GNSS observations from five different campaigns -2012, 2014, 2016, 2018 and 2020- in 13 stations in the area, in order to estimate their Caribbean-fixed velocities, hence the regional cumulative strain. Additionally, we use both InSAR and GNSS data to measure volcanic deformation, aiming to refine the computed velocities by removing volcanic deformation from the tectonic signal.</p><p>The refined velocities allow us to asses a more precise cumulative strain for the Aguacaliente-Navarro fault system, which is useful to improve seismic hazard assessment in Cartago, one of the most important cities in the region.</p>

Carbon and sulfur isotopes in tree rings as a proxy for volcanic degassing

Trees are useful archives of past atmospheric conditions. They have most commonly been used to infer large-scale changes in climate, industrial pollution, and the magnitude and frequency of geological hazards. While geochemical changes in tree rings have been linked to localized anthropogenic smelter pollution, their potential to track geochemical changes in volcanic degassing has not yet been fully realized. Here, we applied a new proxy using sulfur and carbon isotopes in tree rings to examine fluctuations in gas emission at Turrialba volcano, Costa Rica. Since 2009, Turrialba has emitted a persistent gas plume and increasingly frequent explosions and ash eruptions as activity has accelerated. We collected cores from a species of alder tree, Alnus acuminata, at several locations surrounding the volcano. Biannual isotopic analysis of rings demonstrated a notable δ34S shift of –5.2‰ and a similarly sharp δ13C shift of +1.3‰ in trees downwind of the plume following the onset of strong degassing in 2009. We propose that these shifts in the isotopic values of the tree correspond to those of the volcanic SO2 and CO2, and in the case of the δ13C, an additional fractionation caused by leaf impairment from exposure to volcanic SO2. This new proxy can be applied to other volcanoes as a novel method of obtaining a temporal record of degassing, a crucial tool for volcano monitoring.

Implementation of electrochemical, optical and denuder-based sensors and sampling techniques on UAV for volcanic gas measurements: examples from Masaya, Turrialba and Stromboli volcanoes

Volcanoes are a natural source of several reactive gases (e.g., sulfur and halogen containing species) and nonreactive gases (e.g., carbon dioxide) to the atmosphere. The relative abundance of carbon and sulfur in volcanic gas as well as the total sulfur dioxide emission rate from a volcanic vent are established parameters in current volcano-monitoring strategies, and they oftentimes allow insights into subsurface processes. However, chemical reactions involving halogens are thought to have local to regional impact on the atmospheric chemistry around passively degassing volcanoes. In this study we demonstrate the successful deployment of a multirotor UAV (quadcopter) system with custom-made lightweight payloads for the compositional analysis and gas flux estimation of volcanic plumes. The various applications and their potential are presented and discussed in example studies at three volcanoes encompassing flight heights of 450 to 3300 m and various states of volcanic activity. Field applications were performed at Stromboli volcano (Italy), Turrialba volcano (Costa Rica) and Masaya volcano (Nicaragua). Two in situ gas-measuring systems adapted for autonomous airborne measurements, based on electrochemical and optical detection principles, as well as an airborne sampling unit, are introduced. We show volcanic gas composition results including abundances of CO2, SO2 and halogen species. The new instrumental setups were compared with established instruments during ground-based measurements at Masaya volcano, which resulted in CO2 ∕ SO2 ratios of 3.6 ± 0.4. For total SO2 flux estimations a small differential optical absorption spectroscopy (DOAS) system measured SO2 column amounts on transversal flights below the plume at Turrialba volcano, giving 1776 ± 1108 T d−1 and 1616 ± 1007 T d−1 of SO2 during two traverses. At Stromboli volcano, elevated CO2 ∕ SO2 ratios were observed at spatial and temporal proximity to explosions by airborne in situ measurements. Reactive bromine to sulfur ratios of 0.19 × 10−4 to 9.8 × 10−4 were measured in situ in the plume of Stromboli volcano, downwind of the vent.