Cyclotide host-defense tailored for species and environments in violets from the Canary Islands

Cyclotides are cyclic peptides produced by plants. Due to their insecticidal properties, they are thought to be involved in host defense. Violets produce complex mixtures of cyclotides, that are characteristic for each species and variable in different environments. Herein, we utilized mass spectrometry (LC–MS, MALDI-MS), transcriptomics and biological assays to investigate the diversity, differences in cyclotide expression based on species and different environment, and antimicrobial activity of cyclotides found in violets from the Canary Islands. A wide range of different habitats can be found on these islands, from subtropical forests to dry volcano peaks at high altitudes. The islands are inhabited by the endemic Viola palmensis, V. cheiranthifolia, V. anagae and the common V. odorata. The number of cyclotides produced by a given species varied in plants from different environments. The highest diversity was noted in V. anagae which resides in subtropical forest and the lowest in V. cheiranthifolia from the Teide volcano. Transcriptome sequencing and LC–MS were used to identify 23 cyclotide sequences from V. anagae. Cyclotide extracts exhibited antifungal activities with the lowest minimal inhibitory concentrations noted for V. anagae (15.62 μg/ml against Fusarium culmorum). The analysis of the relative abundance of 30 selected cyclotides revealed patterns characteristic to both species and populations, which can be the result of genetic variability or environmental conditions in different habitats. The current study exemplifies how plants tailor their host defense peptides for various habitats, and the usefulness of cyclotides as markers for chemosystematics.

TFgeotourism: A Project to Quantify, Highlight, and Promote the Volcanic Geoheritage and Geotourism in Tenerife (Canary Islands, Spain)

Volcanic landscapes offer a multitude of resources to the communities that live within them. However, the main attraction that volcanoes offer is associated with volcanic heritage and geotourism. The scope of this project is to create and promote emerging geotouristic products through the empowerment of volcano tourism and thus contribute to strengthening the economic and business fabric of the volcanic island of Tenerife (Spain). In Tenerife, this great geodiversity includes the stravolcanoes, shield volcanoes, calderas, cinder cones, maars, tuff cones and rings, and lava fields, all exposed beautifully in cliffs, ravines, beaches, deposits, etc. The main activities of the project associated with the documentation and quantification of the conservation values of the volcanic heritage are the following: production of a documentary on the volcanic geoheritage of Teide volcano, selection of the top 50 sites of geotouristic interest, creation of urban geotourism itineraries, recreation of the itinerary of Alexander von Humboldt, and creation of a web page for the project. This project will deliver an essential resource needed to diversify the leisure activities offered in Tenerife through the volcanic heritage and geotourism. It quantifies the best that Tenerife can uniquely offer and highlights it in a globally accessible and perpetual manner.

Temporal variations of CO2 efflux continuous monitoring at the summit cone of Teide volcano (Tenerife, Canary Islands) during the period1999-2021

<p>Tenerife Island (2034 km<sup>2</sup>), the largest of the Canarian archipelago, is characterized by three main volcano-tectonic axes: the NS, NE and NW rifts and a central caldera, Las Cañadas, hosting the twin stratovolcanoes Pico Viejo and Teide. Although Teide volcano hosts a weak fumarolic system, volcanic gas emissions from the summit cone consist mostly of diffuse CO<sub>2</sub> degassing. The first continuous automatic geochemical station in Canary Islands was installed at the south-eastern foot of summit cone of Teide volcano in 1999, with the aim of improving the volcanic monitoring system and providing a multidisciplinary approach to the surveillance program of Teide volcano. The 1999-2020 time series shows diffuse CO<sub>2</sub> emission values ranging between 0 and 62.8 kgm<sup>-2</sup>d<sup>-1</sup>, with a mean value of 4.3 kgm<sup>-2</sup>d<sup>-1</sup>. Inspection of the CO<sub>2</sub> efflux time series shows significant temporal variations with anomalous values of more than 20 kgm<sup>-2</sup>d<sup>-1</sup> centred at years 2000, 2003, 2005, 2007, 2008, 2012, 2015 and 2016, always before a significant increase in the seismic activity beneath Tenerife Island. With the aim to filter out environmental variables, a multiple regression analysis (MRA) was applied to the first 12 years of the diffuse CO<sub>2</sub> flux time series (1999-2011), recorder on an hourly basis by the station, and we found that soil temperature, soil water content, wind speed and barometric pressure explained 16.7% of variability. The comparison between filtered CO<sub>2</sub> efflux (continuous, hourly, automated station) versus the temporal evolution of diffuse CO<sub>2</sub> emission estimated by ground CO<sub>2</sub> efflux surveys of summit cone of Teide (during summer season on an area of around 0.11 km<sup>2</sup>) for the period 1999-2011 (Pérez et al., 2013), shows a nearly coincident marked peak in December 2001 and a similar shaped evolution from each sampling type as the increase from ~2005 to 2009 and the subsequent decrease from ~2009 to 2011, reaching maximum values of 161.6 and 179.9 t d<sup>-1</sup>, respectively. Seismic activity displayed as of monthly earthquakes (M>1) occurring in and around Tenerife island is well correlated with diffuse CO<sub>2</sub> efflux relevant peaks. In average, the seismicity recorded during the study period was mainly preceded by geochemical anomalies of the registered surface CO<sub>2</sub> efflux by about one year. After we analysed the CO<sub>2</sub> efflux time series by using the Continuous Wavelet Transform (Ricker wavelet) to detect relevant time-frequency patterns in the signal, we found at low frequencies quasi-periodical oscillations with periods of 3-4 years, which might reflect the internal dynamics of the magmatic-hydrothermal system. Moreover, during the intervals of highest levels of CO<sub>2</sub> efflux, the analysis evidenced also oscillations with a period of about 6 months during the interval 1999-2011. Our study reveals that continuous geochemical monitoring data is representative of the same trends in flux that are quantitatively captured by annual surveys, and provides the basis for accurate determination of background values. This combined approach offers a useful template for application to other volcanic systems for the purposes of constructing quantitative dynamic models of hydrothermal systems and identifying processes at depth in near-real-time.</p>

Modelling ground deformation in Tenerife (Canary Islands) during 2003-2010

<p>Tenerife is the biggest island of the Canaries and one of the most active from the volcanological point of view. The island is geologically complex, and its main volcano-tectonic features are three volcanic rifts and the composite volcanic complex of Teide-Las Cañadas. The latter is located in the central part of the island at the intersection of Tenerife principal rifts. Teide volcano, with its 3718 m of elevation constitutes the most prominent topographical feature of the island. Being a densely populated active volcanic island, Tenerife is characterised by a high volcanic risk. For this reason, the island requires an advanced and efficient volcano monitoring system. Among the geophysical parameters that could be useful to forecast an oncoming volcanic eruption, the ground deformation is relevant for detecting the approach of magma to the surface.</p><p>This study aim is to analyse the ground deformation in the surroundings of the Teide-Las Cañadas complex.  For this purpose, we studied the ground deformation of Tenerife by using a set of Synthetic Aperture Radar (SAR) images acquired between 2003 and 2010 by the ENVISAT ASAR sensor and processed through a DInSAR-SBAS technique. The DInSAR SBAS time series revealed a ground deformation in the central part of the island, coinciding with the Teide volcano. A similar deformation was already evidenced by Fernández et al. (2009) from 2004 to 2005.</p><p>We investigated the source of this ground deformation by applying the statistical tool of Independent Component Analysis (ICA) to the dataset. ICA allowed separating the spatial patterns of deformation into four components. We attributed three of them to an actual ground deformation, while the fourth seems to be only related to the noise component of data. The first component (ICA1) displays a spatial pattern localised in Teide volcano neighbourhoods and consists of a ground uplift of few centimetres. The deformation associated with this component starts in 2005 and persists along the rest of the time series. The second component (ICA2) of the ground deformation is localised in the South/South-West part of Las Cañadas rim while the third component (ICA3) is localised to the East of Teide volcano. We performed inverse modelling to analyse the source of the ground deformation related to ICA1 to retrieve the location, the geometry and the temporal evolution of this source. The inversion was based on analytical models of ground deformation as well as on Finite-Element-Modelling. The result showed that the ground deformation is associated with a shallow sill-like structure, located beneath Teide volcano, possibly reflecting a hydrothermal reservoir. The knowledge of this source geometry could be of significant interest to better understand ground deformation data of possible future volcanic crisis. </p>

Long-term variations of diffuse CO2, He and H2 at the summit crater of Teide volcano, Tenerife, Canary Islands

<p>Tenerife (2,034 km<sup>2</sup>) is the largest of the Canary Islands. Its structure is controlled by a volcano-tectonic rift-system with NW, NE and NS directions, with the volcanic system Teide-Pico Viejo located in the intersection. Teide is 3,718 m.a.s.l. high and its last eruption occurred in 1798 through an adventive cone of Teide-Pico Viejo volcanic complex. Persistent degassing activity, both visible and diffuse, takes place at the summit cone of the volcano, being the diffuse degassing the principle mechanism.</p><p>During the period 1999-2020, more than 200 diffuse CO<sub>2</sub> efflux surveys have been performed in the summit crater of Teide Volcano. For each survey, 38 sampling sites homogeneously distributed inside the crater covering an area of 6,972 m<sup>2</sup> were selected. Diffuse CO<sub>2</sub> emission was estimated in each point by means of a portable non dispersive infrared (NDIR) CO<sub>2</sub> fluxmeter using the accumulation chamber method. Additionally, soil gas samples were taken at 40 cm depth and analyzed later in the lab for the He and H<sub>2</sub> content by means of quadrupole mass spectrometry and micro-gas chromatography, respectively. To estimate the He and H<sub>2</sub> emission rates at each sampling point, the diffusive component was estimated following the Fick’s law and the convective emission component model was estimated following the Darcy’s law. In all cases, spatial distribution maps were constructed averaging the results of 100 simulations following the sequential Gaussian simulation (sGs) algorithm, in order to determine CO<sub>2</sub>, He and H<sub>2</sub> emission rates.</p><p>During the study period, CO<sub>2</sub> emissions ranged from 2.2 to 176.1 t/d, He emissions between 0.013 and 4.1 kg/d and H<sub>2</sub> between 1.3 and 35.6 kg/d. On October 2, 2016, a seismic swarm of long-period events was recorded on Tenerife followed by a general increase of the seismic activity in and around the island (D’Auria et al., 2019). Since then, relatively high values have been obtained in the diffuse CO<sub>2</sub>, He and H<sub>2</sub> emission rate the crater of Teide. This increase reflects a process of pressurization of the volcanic-hydrothermal system.</p><p>The variations in CO<sub>2</sub>, He and H<sub>2</sub> emissions indicate changes in the activity of the system and can be useful to understand the behaviour of the volcanic system and to forecast future volcanic activity. Monitoring the diffuse degassing rates at Teide volcano has demonstrated to be an essential tool for predicting future seismic–volcanic unrest, and has become important to reduce volcanic risk in Tenerife (Melián et al., 2012; Pérez et al., 2013).</p><p>D'Auria .L, Barrancos J., Padilla G.D., Pérez N.M., Hernández P.A., Melián G., Padron E., Asensio-Ramos M., García‐Hernández R. (2019). J. Geophys. Res. 124, 8739-8752</p><p>Pérez N. M., Hernández P. A., Padrón E., Melián G., Nolasco D., Barrancos J., Padilla G., Calvo D., Rodríguez F., Dionis S. and Chiodini G. (2013). J. Geol. Soc., 170(4), 585-592.</p><p>Melián G., Tassi F., Pérez N. M., Hernández P., Sortino F., Vaselli O., Padrón E., Nolasco D., Barrancos J., Padilla G., Rodriguez F., Dionis S., Calvo D., Notsu K., Sumino H. (2012).  Bull. Volcanol, 74(6), 1465-1483.</p><p> </p>

Prospects of Autonomous Volcanic Monitoring Stations: Experimental Investigation on Thermoelectric Generation from Fumaroles

Fumaroles represent evidence of volcanic activity, emitting steam and volcanic gases at temperatures between 70 and 100 ∘ C . Due to the well-known advantages of thermoelectricity, such as reliability, reduced maintenance and scalability, the present paper studies the possibilities of thermoelectric generators, devices based on solid-state physics, to directly convert fumaroles heat into electricity due to the Seebeck effect. For this purpose, a thermoelectric generator composed of two bismuth-telluride thermoelectric modules and heat pipes as heat exchangers was installed, for the first time, at Teide volcano (Canary Islands, Spain), where fumaroles arise in the surface at 82 ∘ C . The installed thermoelectric generator has demonstrated the feasibility of the proposed solution, leading to a compact generator with no moving parts that produces a net generation between 0.32 and 0.33 W per module given a temperature difference between the heat reservoirs encompassed in the 69–86 ∘ C range. These results become interesting due to the possibilities of supplying power to the volcanic monitoring stations that measure the precursors of volcanic eruptions, making them completely autonomous. Nonetheless, in order to achieve this objective, corrosion prevention measures must be taken because the hydrogen sulfide contained in the fumaroles reacts with steam, forming sulfuric acid.

Short-term variations of diffuse CO2 and H2S at the summit crater of Teide volcano, Tenerife, Canary Islands

<p>Tenerife (2,034 km<sup>2</sup>) is the central and largest island of the Canarian archipelago, located about 100 km west of the African coast between 27º37’ and 29º25’N and between 13º20’ and 18º10’W. The structure of Tenerife is controlled by a volcano-tectonic rift-system with NW, NE and NS directions with Teide volcano located in the intersection of the three rifts. Teide is the highest stratovolcano in the Atlantic Ocean reaching 3,718 m.a.s.l. with its last eruption occurred in 1798 through an adventive cone of Teide-Pico Viejo volcanic complex. Persistent degassing activity, both visible and diffuse, takes place at the summit cone of the volcano, being the diffuse degassing the principle degassing mechanism of Teide (Mori et. al., 2001; Pérez et. al., 2013). As part of the volcanic monitoring program of INVOLCAN in Tenerife, 8 surveys were performed during summer 2019 in order to evaluate the short term variations of diffuse CO<sub>2</sub> and H<sub>2</sub>S emissions in the summit crater. The emissions were calculated using data from 38 sampling sites homogeneously distributed inside the crater covering an area of 6,972 m<sup>2</sup> by means of a portable CO<sub>2</sub> and H<sub>2</sub>S fluxmeter using the accumulation chamber method (Parkinson 1981). During the study period, CO<sub>2</sub> and H<sub>2</sub>S emissions ranged from 33 ± 5 to 93 ± 25 t/d and from 0.6 ± 0.2 to 4 ± 0.1 kg/d, respectively. Despite the small changes observed in the temporal evolution, values are considered normal for a quiescence period in Teide volcanic system. Short term variations in CO<sub>2</sub> and H<sub>2</sub>S emissions indicate changes in the activity of the system and can be useful to understand the behaviour of the volcanic system and as forecast of future volcanic activity.</p><p><strong>References<br></strong>Mori T. et al. (2001). Chemical Geology, 177, 85–99.<br>Parkinson K. J. (1981). Journal of Applied Ecology, 18, 221–228.<br>Pérez N. M. et al. (2013). Journal of the Geological Society, 170, 585–592.</p>

Characterizing the long-period seismicity of Teide volcano in Tenerife (Canary Islands, Spain)

<p>The volcanic long-period seismicity, composed of long-period events and volcanic tremors, constitutes an important attribute of volcanic unrest. Its detection and characterization is therefore a key aspect of volcano monitoring. In the present work, a method based on the seismic network covariance matrix, the equivalent in the frequency domain of the cross-correlation matrix, is used to automatically detect and locate long-period events of the Teide volcano on the island of Tenerife (Canary Islands, Spain). The method is based on the analysis of eigenvalues and eigenvectors of the network covariance matrix.</p><p>Long-period events are detected through the time evolution of the width of the network covariance matrix eigenvalues distribution, which is a proxy of the number of sources acting in the wavefield. Each detected long-period event is then located using the moveout information of the corresponding first eigenvector. Three years of seismic data (from 2017 to 2019) continuously recorded by the Red Sísmica Canaria (C7), a permanent monitoring network composed of 17 broadband stations operated by the Instituto Volcanológico de Canarias (INVOLCAN), are analysed. The obtained locations are compared with potential locations from INVOLCAN’s catalog, obtained by a standard approach based on manual phases picking.</p>

Wavelet analysis of geochemical time series: continuous CO2 flux measurements at the summit cone of Teide volcano, Tenerife, Canary Islands

<p>Tenerife Island (2034 km<sup>2</sup>) is the largest of Canarian archipelago and is characterized by three main volcano-tectonic axis: the NS, NE and NW dorsals and a central caldera, Las Cañadas, hosting the twin stratovolcanoes Pico Viejo and Teide. Although Teide volcano shows a weak fumarolic system, volcanic gas emissions observed in the summit cone consist mostly of diffuse CO<sub>2</sub> degassing. The first continuous automatic geochemical station in Canary Islands was installed at the south-eastern foot of summit cone of Teide volcano in 1999, with the aim of improving the volcanic monitoring system and providing a multidisciplinary approach to the surveillance program of Teide volcano. The 1999-2011 time series show anomalous changes of the diffuse CO<sub>2</sub> emission with values ranging between 0 and 62.8 kg m<sup>-2</sup>d<sup>-1</sup>, with a mean value of 4.7 kg m<sup>-2</sup>d<sup>-1</sup>. The CO<sub>2</sub> efflux increases remained after filtering the time series with multiple regression analysis (MRA), were soil temperature, soil water content, wind speed and barometric pressure explained 16.7% of variability.</p><p>We analysed the CO<sub>2</sub> efflux time series by using the Continuous Wavelet Transform, with the Ricker wavelet, to detect relevant time-frequency patterns in the signal. The wavelet analysis showed, at low frequencies, quasi-periodical oscillations with periods of 3-4 years. Moreover, during the intervals of highest levels of CO<sub>2</sub> efflux the analysis evidenced also oscillations with a period of about 6 months.</p><p>Our data show in 2002 a marked peak of the filtered CO<sub>2</sub> signal. The beginning of this increase is nearly coincident with a similar signal on the data of CO<sub>2</sub> emission, coming from periodic surveys performed yearly on the area of Teide summit cone since 1997. We interpret these signals as an “early warning” associated to the 2004 seismo-volcanic unrest in Tenerife. A similar coincidence was observed also for the interval 2006-2009, which was followed by an increase in the local seismicity of Tenerife as well, characterized both by an increasing number of small earthquakes occurring, respectively, mostly along the NW dorsal and in the southern part of the NE dorsal of Tenerife.</p><p>Our study reveals that wavelet analysis on the continuous CO<sub>2</sub> efflux measurement could help to detect anomalous degassing periods, possibly indicating impending seismo-volcanic unrest episodes and/or eruptions. Finally, it is important to remark that the data presented in this work, constitute one of the longest time series of continuous CO<sub>2</sub> efflux measurements in an active volcanic area, hence providing an important benchmark for similar measurements worldwide.</p>