Emissions of Fe(II) and its kinetic of oxidation at Tagoro submarine volcano, El Hierro

The eruptive process that took place in October 2011 in the submarine volcano Tagoro off the Island of El Hierro and the subsequent degasification stage, five months later, have increased the concentration of TdFe(II) (Total dissolved iron(II)) in thewaters nearest to the volcanic edifice. In order to detect any variation in concentrations of TdFe(II) due to hydrothermal emissions, three cruiseswere carried out two years after the eruptive process in October 2013,March 2014 andMay 2015. The results fromthese cruises confirmed important positive anomalies in TdFe(II), which coincided with negatives anomalies in pHF,is (pH in free scale, at in situ conditions) located in the proximity of themain cone. Maximumvalues in TdFe(II) both at the surface, associated to chlorophyll a maximum, and at the sea bottom, were also observed, showing the important influence of organic complexation and particle re-suspension processes. Temporal variability studies were carried out over periods ranging from hours to days in the stations located over themain and two secondary cones in the volcanic edifice with positive anomalies in TdFe(II) concentrations and negative anomalies in pHF,is values. Observations showed an important variability in both pHF,is and TdFe(II) concentrations, which indicated the volcanic area was affected by a degasification process that remained in the volcano after the eruptive phase had ceased. Fe(II) oxidation kinetic studies were also undertaken in order to analyze the effects of the seawater properties in the proximities of the volcano on the oxidation rate constants and t1/2 (half-life time) of ferrous iron. The increased TdFe(II) concentrations and the low associated pHF,is values acted as an important fertilization event in the seawater around the Tagoro volcano at the Island of El Hierro providing optimal conditions for the regeneration of the area.En prens

Physico-chemical, biological and geological study of an underwater volcano in a degassing stage: Island of El Hierro

El objetivo principal del proyecto “Physico-chemical, biological and geological study of an underwater volcano in a degassing stage: Island of El Hierro”, (VULCANO-II) es estudiar, desde un punto de vista totalmente interdisciplinar, la fase de desgasificación activa del único volcán submarino monitoreado desde su nacimiento en aguas españolas. De esta forma, se pretende además, dar continuidad a los estudios multidisciplinares realizados sobre el volcán submarino de la isla de El Hierro en el contexto del proyecto del Plan Nacional VULCANO-I, (CTM2012-36317) y VULCANA (Vulcanología Canaria Submarina, IEO). Para ello, se realizará la monitorización de las propiedades físico-químicas, biológicas y geológicas del proceso eruptivo submarino de la isla de El Hierro y otros puntos sensibles, como el volcán de Enmedio entre Gran Canaria y Tenerif

Changes in the redox and acid-base properties of the seawater due to the hydrothermal emissions of the Tagoro submarine volcano

The character reduced and acid of the emissions associated to the Tagoro submarine volcano allowed to detect the anomalies related with changes in the chemical potential and the proton concentration using ORP and pH sensors, respectively. Detailed surveys of the volcanic edifice were carried out between 2014 and 2016 using several CTD-pHORP tow-yo studies, localizing the ORP and pH changes, which were used to obtain surface maps of anomalies. Moreover, meridional tow-yos were used to calculate the amount of volcanic CO2 added to the water column. The inputs of CO2 along multiple sections combined with measurements of oceanic currents produced an estimated volcanic CO2 flux = 6.0 105 ± 1.1 105 kg d-1 which increases the acidity above the volcano by ~20%. In order to investigate the temporal variability of the system, CTD-pH-ORP yo-yo studies were also conducted that included discrete sampling for carbonate system parameters and total dissolved Fe(II), TDFe(II). Important anomalies in both pHT and TDFe(II) were observed from these studies. The increased in the TDFe(II) concentrations and the low associated pHT, that decrease the rate of oxidation of Fe(II), may be acting as an important fertilization event in the seawater around the volcano at the Island of El Hierro providing optimal conditions for the biological regeneration of the area. Fe(II) oxidation kinetic studies were also undertaken in order to analyze the effects of the seawater properties in the proximities of the volcano on the oxidation rate constants and t1/2 (half-life time) of ferrous iron

Significant Release of Dissolved Inorganic Nutrients From the Shallow Submarine Volcano Tagoro (Canary Islands) Based on Seven-Year Monitoring.

Tagoro, the shallow submarine volcano that erupted south of El Hierro (Canary Islands, Spain) in October 2011, has been intensely monitored for over 7 years, from the early eruptive stage to the current degassing stage characterized by moderate hydrothermal activity. Here, we present a detailed study of the emissions of inorganic macronutrients (NO2 − + NO3 −, PO4, and Si(OH)4) comprising a dataset of over 3300 samples collected through three different sampling methodologies. Our results show a significant nutrient enrichment throughout the whole studied period, up to 8.8-fold (nitrate), 4.0-fold (phosphate), and 16.3-fold (silicate) in the water column, and larger enrichments of phosphate (10.5-fold) and silicate (325.4-fold), but not of nitrate, in the samples collected directly from the vents. We also provide some preliminary results showing ammonium (NH4 +) concentrations up to 1.97 µM in the vent fluids as compared to 0.02 µM in the surrounding waters. Nutrient fluxes from the volcano during the degassing stage were estimated as 3.19 ± 1.17 mol m−2 year−1 (NO2 − + NO3 −), 0.02 ± 0.01 mol m−2 year−1 (PO4), and 0.60 ± 1.35 mol m−2 year−1 (Si(OH)4), comparable to other important nutrient sources in the region such as fluxes from the NW-African upwelling. Nutrient ratios were affected, with a minimum (NO3 − + NO2 −):PO4 ratio of 2.36:1; moreover, a linear correlation between silicate and temperature enabled the use of this nutrient as a mixing tracer. This study sheds light on how shallow hydrothermal systems impact the nutrient-poor upper waters of the ocean

Informe de Campaña - Vulcana0316 - Marzo 2016

El objetivo principal del proyecto Vulcana (Vulcanología Canaria Submarina), es evaluar el grado de afección y la recuperación sobre el ecosistema marino del volcán submarino Tagoro de la isla de El Hierro, haciéndolo extensible a otras regiones de posible interés hidrotermal o vulcanológico. Para ello, se realizará un estudio completo de las propiedades físico-químicas, biológicas y geológicas en las áreas descritas.Versión de edito