La Restinga Research Articles

Ecosystem modeling to evaluate the ecological sustainability of small-scale fisheries: A case study from El Hierro, Canary Islands

This paper examines various fishery management scenarios based on the recovery of small-scale fisheries (SSF) following a submarine volcanic eruption in 2011 in El Hierro Island (Canary Islands, Spain). After this catastrophic event, the SSF composition of La Restinga fishing community was affected by socio-economic and demographic changes. The uncertainty derived from this situation provides an opportunity to evaluate the fisheries’ sustainability and advice on different management options under an ecosystem-based approach. The Ecopath with Ecosim modeling framework was used to build a model of El Hierro Island, where the versatile and traditional multispecies small-scale fleet of La Restinga operates. Our main goal is to improve traditional fisheries, based on the relevance of key local fisheries and multi-specific fishery strategies in the light of scientific knowledge. Temporal simulations for the next decade were analyzed by creating scenarios of alternative fishing effort distributions based on the fishing trends observed in El Hierro small-scale community of La Restinga after a natural hazard. The outcomes of this modeling prototype show the vulnerability of some littoral and demersal species, the resilience of migratory species, and the sustainability of SSF diversification practices. These results could develop an adaptive and co-management strategy with the local fishing community to preserve the small-scale fishing system and marine resources.

Small but strong: Socioeconomic and ecological resilience of a small European fishing community affected by a submarine volcanic eruption

Small-scale coastal fishing communities are facing many new challenges, such as rapid ecological changes created by anthropogenic and natural events like earthquakes or volcanic eruptions. This paper explores how a coastal population has responded to such an event and highlights the diverse coping strategies used to tackle it. This research was conducted on the island of El Hierro (Spain), where a submarine volcanic eruption occurred in 2011, affecting a multiple-use Marine Protected Area (MPA) and the nearby fishing community of La Restinga. Our study illustrates how the local population coped with this situation by combining multiple monetary and non-monetary activities (e.g., informal exchanges) as well as the role of institutions in increasing local resilience by supporting fishers' demands and allowing their participation in the decision-making process in the immediate wake of a catastrophic event. Local families also exploited various natural resources in and near the MPA, thus ensuring access to crucial marine resources and continued recreational/cultural services. The results suggest that collective action played a key role in the recovery process after the eruption, creating some advantages for different local groups despite the hazardous nature of the event.

Reconstruction of the subaerial Holocene volcanic activity through paleomagnetic and 14C dating methods: El Hierro (Canary Islands)

Volcanic hazard assessment relies on the accurate knowledge of the eruptive style and recurrence of volcanic eruptions in the past. At El Hierro (Canary Islands) historical and prehistorical records are still poorly defined, and although the island was the location of one of the most recent eruptions (La Restinga, 2011 CE) of the Canarian archipelago, the recent subaerial volcanism is still poorly studied. Information about the age of Holocene volcanic activity as well as the stratigraphy of the deposits is scarce: few eruptions are dated so far, whereas the others are classified as pre-or Holocene events considering lava flow characteristics along the coast.Here, we report on the dating of eleven (Mña Chamuscada, Mña del Tesoro, Orchilla, Las Calcosas, Mña Negra, Lomo Negro, Below Lomo Negro, Cuchillo del Roque, Malpaso Member, and Mña del Guanche) Holocene subaerial eruptions, distributed along the three rift zones, combining paleomagnetic and 14C methods. We also provide geochemical analyses for nine of them. Results indicate that Mña Chamuscada and Mña del Tesoro occurred more recently than previously considered, setting them within the last two thousand years. Conversely, paleomagnetic and 14C ages found for Lomo Negro eruption are consistent with literature data (Villasante-Marcos and Pavón-Carrasco, 2014) and constrain the occurrence of this event in the XVI century CE. Finally, for Malpaso Member deposits, the two 14C datings obtained by charcoals found below and above the trachytic layer set the eruption during the Holocene epoch, between ~7300 BCE and ~4700 BCE. For the other eruptions, in two cases (Orchilla and Las Calcosas) many possible time windows during the last 14 ka have been found, whereas a few possible ages have been obtained for the others. On the whole, the resulting chronological reconstruction of the recent activity of El Hierro indicates that eruptions occurred unevenly along the three main rifts, with nine eruptions in the WNW rift, six in the NE rift, and four in the SSE rift. We document at least two periods characterized by high eruptive frequency: an old one, between 8000 BCE and 1000 BCE, with eight eruptions, three of which characterized by more evolved compositions (phonotephrite and trachyte), and a recent one, between 1000 BCE and present day, with at least seven eruptions, mainly showing basanite compositions. The new data yield a significant improvement of Holocene eruption chronology, thus are instrumental for a correct evaluation of the volcanic hazard at El Hierro.

Bioprospecting Antiproliferative Marine Microbiota From Submarine Volcano Tagoro

Marine ecosystems are unique and rich reservoirs of biodiversity with high potential toward improving the quality of human life. The extreme physical–chemical conditions of the oceans have favored marine organisms to produce a great variety of new molecules as a mechanism to ensure their survival, and such compounds possess great biopharmaceutical interest. In particular, marine microbiota represent a promising and inexhaustible source for the development of new drugs. This work presents the taxonomic study of the samples obtained from the underwater volcano Tagoro, which has allowed us to develop a collection of 182 marine bacterial strains. On October 10th, 2011, at La Restinga–El Mar de Las Calmas Marine Reserve, an underwater eruption gave rise to a novel shallow submarine volcano at 1.8 km south of the island of El Hierro, Canary Islands, Spain. During the first 6 months, extreme physical–chemical perturbations, comprising thermal changes, water acidification, deoxygenation, and metal enrichment, resulted in significant alterations of the marine ecosystem. After March 2012, the submarine volcano Tagoro entered an active hydrothermal phase that involved a release of heat, gases, metals, and micronutrients that continues till our present. During 2016, our research team had the opportunity to participate in one of the monitoring oceanographic cruises carried out in the area in order to isolate microorganisms associated with both rock samples and deep-sea invertebrates over Tagoro submarine volcano. In this study, Proteobacteria revealed as the most abundant Phylum with 70.2% among all isolated strains, followed by Firmicutes 19%, Actinobacteria 9.5%, and Bacteroidetes 1.2%. Furthermore, we present the results of the antiproliferative assays of the extracts obtained from small-scale cultures of selected bacterial strains. An analysis of the effects of culture conditions in the antiproliferative activity showed that strains grown in Marine Broth (MB) presented lower GI50 values than those cultured in a modified medium (MM1). This effect is improved when the strains are incubated under agitation conditions. The antiproliferative potential of genera such as Halobacillus, Kangiella, Photobacterium, and Halomonas is revealed. Their biotechnological development provides an excellent starting point to access novel secondary metabolites and enzymes with potential for pharmaceutical and industrial applications.

Underwater records of submarine volcanic activity: El Hierro (Canary Islands 2011–2012) eruption

We present the monitoring of a submarine volcanic eruption that took place near the southernmost emerged land of El Hierro Island (Canary Islands, Spain), from October 2011 to February 2012. Right after the onset of the eruption, in mid-October 2011, we deployed an offshore geophone array for the purpose of monitoring the submarine eruptive activity signals. It acquired continuous data from October 2011 to May 2012, sometime after the end of the eruption. The array consisted of 8 high-frequency, 3-component geophones assembled into a cable string, with 6 m of separation. The geophone string was installed in La Restinga Harbor at a distance of less than 2 km from the volcanic edifice. The dataset acquired with the array is a unique continuous acoustic record of the activity associated with this eruption. We analyzed the continuous signal of the eruptive activity, with special interest in those events reflecting the eruption dynamics. Our results show that the geophone array was recording acoustic waves from a back-azimuth source corresponding to the position of the submarine vent, traveling at a speed of 1510 m/s, compatible with the speed of sound in water. Acoustic data shows a good correlation with the seismic data recorded on land for the case of earthquake occurrence. In addition, it provides relevant information towards the understanding of the eruptive surface activity. Therefore, this methodology can be successfully used in cases of submarine eruptions.

Historical records and increasing trends of Caribbean Flamingos (Phoenicopterus ruber) on Margarita Island, Venezuela

ABSTRACTThe Caribbean Flamingo (Phoenicopterus ruber) has been a species of conservation concern since the 1960s because of its regional population decline and loss of breeding colonies. In the last two decades, there have been reports of increasing population trends in the Caribbean. The aim of this work is to document the historic population status of flamingos on Margarita Island, Venezuela, and to present an account of their recovery since 2006. In the first half of the twentieth century, flamingos were present on Margarita Island in one location (La Restinga lagoon) in variable numbers (100–800); however, in the 1980s and 1990s, they almost disappeared from the island. In 2006, a group of nine was recorded. During the following years, the population increased in number and expanded eastward on the island. Today, the population size range 1 600–2 000 individuals, are present regularly in at least eight lagoons, and two breeding colonies have been reported. Several threats are still present in the island that can revert the positive population trend. The recovery of the population in Margarita Island is a consequence of successful regional conservation efforts and the maintenance of wetlands with appropriate conditions for the species, particularly in protected areas.

A micro-Raman and X-ray study of erupted submarine pyroclasts from El Hierro (Spain) and its' astrobiological implications

The pumice volcanic samples could have possible connections to the evolution of life and give us insight about their bio-geochemical processes related. In this regard, the samples from the volcanic eruption from La Restinga (El Hierro, Spain) in 2011 have been mainly studied by means of Raman spectroscopy. The research also includes analysis of XRD, Scanning Electron Microscopy and Optical Microscopy to support the Raman analysis. The results show that the Raman methods and mineral analyses are in strong agreement with the results obtained from other authors and techniques. The internal white foamy core (WFC) of the studied pumice samples shows amorphous silica, Fe-oxides, Ti-oxides, quartz, certain sulfates, carbonates, zeolites and organics. On the other hand, the external part (dark crust – DC) of these samples mainly presents primary-sequence mineralogy combined with some secondary alteration minerals such as olivine, feldspar, pyroxene, amorphous silica, and Fe-oxide. Raman spectroscopy detected other minerals not yet reported on these samples like barite, celestine and lepidocrocite. Also, the different chemometric and calibration methods for Raman spectroscopy in elemental composition, mineral classification and structural characterization has been successfully applied.From the astrobiological perspective, the research was also complemented with comparisons to other similar samples from terrestrial analogs. The main consideration was taking into account the proposed hypothesis regarding the potential behavior of the pumice as a substrate for the evolution of life. Furthermore, the detailed analysis from La Restinga eruption is coherent with the mineral phases and processes discussed from previous literature. The white internal part fulfills the conditions to work as an organic reservoir, confirmed by the detection of organic matter and selected minerals that could be used as energy sources for bacterial communities. The external layers of the samples work as a shielding layer to protect the organics from decay in extreme conditions. Finally, here we have demonstrated that the characteristics and advantages of Raman spectroscopy could help to assess and understand the possible biogenicity and alteration processes of any geological sample to be found on Mars.

Synergy as strategy: learning from La Restinga, Canary Islands

In this paper, we draw attention to the role of synergies in marine conservation and community sustainability. Using marine protected areas (MPAs) as examples, we argue that MPAs that are carefully designed to fit the existing social systems can be instrumental in synergy building and fostering community development. Such synergy creation is an essential governance strategy that helps enhance governability as it reduces conflicts and provides opportunities for constructive cooperation among stakeholders, especially in times of crisis. We illustrate this using the case of La Restinga MPA in the Canary Islands. Based on data and experiences from long-term research programs on coastal communities in the Canary Islands in general, and La Restinga in particular, we discuss the functions of the MPA in the local contexts and describe how the MPA has transformed relationships and interactions among stakeholders, leading to different levels of synergies. While some of the interactions have not been conducive to the implementation of the MPA, strong synergies have been created, especially after the volcano eruption. The story of La Restinga offers valuable lessons about the way the community copes and responds to change, and the role that synergies play in the process.

Spatial distribution patterns, abundance and reproductive effort of the starfish Echinaster (Othilia) paucispinus along an environmental gradient in a Caribbean mangrove ecosystem

Asteroids of the genus Echinaster are key predators in several benthic coastal ecosystems. Despite their ecological importance, little is known about the population biology of these species, including the response to coastal environmental heterogeneity. This manuscript aims to describe population features (spatial distribution, abundance and density) and reproductive traits of Echinaster (Othilia) paucispinus in a hypersaline wetland under the hypotheses of potential effects of the environmental gradient. Along the gradient, the densities of E. (O.) paucispinus were far higher than any previously reported for this genus. Strong zonation patterns were detected for size, fertility and abundance; however, instead of spatial variation associated with the environmental gradient, the differences were detected between the center and the extremes of the gradient. The extremes were inhabited by more dispersed, larger, mature organisms, while the intermediate region was characterized by high densities of aggregated, small, immature individuals. Temporal variability in reproductive characteristics was considerably lower than spatial variability. Based on these results, it seems that the population of E. (O.) paucispinus at Laguna de La Restinga is governed by pre-settlement processes, rather than by environmental variability along the gradient.

Sea anemones (Cnidaria: Actiniaria, Corallimorpharia, Ceriantharia, Zoanthidea) from marine shallow-water environments in Venezuela: new records and an updated inventory

This study compiles the diversity of sea anemones in different shallow habitats (i.e. rocky shores, coral reefs, mangroves and sandy bottoms) in several locations of Venezuela, including the most important marine reserves of Venezuela: Morrocoy National Park, Mochima National Park, Archipielago de Los Roques National Park, Laguna de La Restinga National Park, Isla de Cubagua, and Chichiriviche de la Costa. Twenty-six species of sea anemones sensu lato were documented, from which only two actiniarian species are newly recorded in Venezuela. In addition, specimens of the scientific collection of the Museo Oceanologico Hermano Benigno Roman, of Isla de Margarita, Venezuela, were examined and its taxonomic status updated. The diversity of sea anemones in Venezuela is updated to 44 species. An illustrated guide of living specimens and short descriptions of the external anatomy of the specimens is included to facilitate sea anemone species identification in the field and to provide a base line for ecological studies that require accurate identification to species level.

Analysis of the intersexual variation in Thalassophryne maculosa fish venoms

Gender related variation in the molecular composition of venoms and secretions have been described for some animal species, and there are some evidences that the difference in the toxin (s) profile among males and females may be related to different physiopathological effects caused by the envenomation by either gender. In order to investigate whether this same phenomenon occurs to the toadfish Thalassophryne maculosa, we have compared some biological and biochemical properties of female and male venoms. Twenty females and males were collected in deep waters of the La Restinga lagoon (Venezuela) and, after protein concentration assessed, the induction of toxic activities in mice and the biochemical properties were analyzed. Protein content is higher in males than in females, which may be associated to a higher size and weight of the male body. In vivo studies showed that mice injected with male venoms presented higher nociception when compared to those injected with female venoms, and both venoms induced migration of macrophages into the paw of mice. On the other hand, mice injected with female venoms had more paw edema and extravasation of Evans blue in peritoneal cavity than mice injected with male venoms. We observed that the female venoms had more capacity for necrosis induction when compared with male venoms. The female samples present a higher proteolytic activity then the male venom when gelatin, casein and FRETs were used as substrates. Evaluation of the venoms of females and males by SDS-PAGE and chromatographic profile showed that, at least three components (present in two peaks) are only present in males. Although the severity of the lesion, characterized by necrosis development, is related with the poisoning by female specimens, the presence of exclusive toxins in the male venoms could be associated with the largest capacity of nociception induction by this sample.

Aspectos reproductivos de <i>Chicoreus brevifrons</i> (Lamarck, 1822) (Neogastropoda: Muricidae) de la laguna de La Restinga, isla de Margarita, Venezuela

Chicoreus brevifrons is characterized by being carnivorous, necrophagous, and relatively abundant in Venezuelan coasts, where it has an economic and ecological importance since it preys on oysters and other mollusks in marine environments and culture systems. This study aims at analyzing some reproductive aspects of the species in La Restinga lagoon, Margarita Island, Venezuela, at four stations from inside to outside of this lagoon. Samples were taken monthly and were used to determine sex ratio; in addition, some eggs were also taken from the site, for description and observation of initial growth of the species. C. brevifrons is characterized for being dioecious, clearly distinguishable for the presence of a penis in males and a vagina and albumin capsule in females. In general, sex ratio was 1:1, although females were more abundant than males during some months. Eggs from C. brevifrons are cluster-like, with 65 to 165 small white capsules. While the organisms develop inside the capsules, they are brown upon spawning, which takes place 45-50 days after they are laid. Initial sizes were between 1.60 mm and 2.56 mm of TL. Further biological and populations studies of this species are recommended in order to know more about its ethology, commercial importance and how they affect mollusk cultures.

New insight into the 2011-2012 unrest and eruption of El Hierro Island (Canary Islands) based on integrated geophysical, geodetical and petrological data

<p>A shallow water eruption started on October 10, 2011, ~2 km south off the coast of El Hierro (Canary Islands, Spain). The eruption lasted about five months and ended by early March 2012. Three months of unrest preceded this event with more than 10,000 localized earthquakes and up to 6 cm of vertical ground deformation. In the Canary Islands, this is the first eruption to be monitored by the network of Instituto Geográfico National (IGN) since the very beginning of the seismic unrest. This provided unprecedented time series that include geophysical (seismic and gravimetric), geodetic, geochemical and petrological data. In this work we discuss and interpret these data in order to describe the mechanisms of 2011-2012 El Hierro eruption, including ascent from magmatic source, a crustal storage, and the final intrusion in the South Rift before the eruption. Our research approach provides a multidisciplinary view of the dynamics of magma ascent and improves previous interpretations formulated during or shortly after the end of the eruption. According to our results, a major intrusion occurred beneath and around preexisting high-density magmatic bodies, localized at depth below the central part of the island. After a failed attempt to reach the surface through a low fractured zone located below the central-northern part of the island, the ascending magma finally found its way nearby the El Hierro South Rift Zone and erupted off the coast of La Restinga village, 350 m below sea level. The eruption was fed by the ascent of an important volume of material from the upper mantle that was emplaced near the crust-mantle boundary and progressively tapped during the eruption.</p>

Aspectos biológicos básicos de <i>Pinctada imbricata</i> (Bivalvia: Pteriidae) en la laguna de La Restinga, isla de Margarita, Venezuela

Pearl oysters are abundant bivalves in the northeastern coast of South America that form dense shoals in the Caribbean Sea, where they are exploited for marketing, making them a valuable resource in northeastern Venezuela. In order to provide information on Pinctada imbricata in the La Restinga Lagoon, its growth, size structure, condition index and natural mortality were estimated from April 2012 to January 2013. A total of 40 random samples of pearl oysters were collected on a monthly basis by freediving in a linear transect of approximately 200 m. The total length and total weight ratio indicated a negative allometric growth. A multimodal distribution was shown in almost all sampling months, with sizes ranging between 21.56 and 54.61 mm of total length. The modal peak observed in most of the months was between 24 and 28 mm, indicating a continuous recruitment throughout the year. The maximum peak of the monthly condition index was in May 2012, while the minimum was in November 2012. Growth parameters were L∞ = 68.5 mm, K = 1.18/year and t0 = 0.37, reaching the regulatory market size of 50 mm at approximately 18 months, with an estimated 2.92 year maximum longevity. Total mortality, corresponding to natural mortality M, was calculated as Z = 1.40/year.

Seismic tomography model reveals mantle magma sources of recent volcanic activity at El Hierro Island (Canary Islands, Spain)

SUMMARY We present a 3-D model of P and S velocities beneath El Hierro Island, constructed using the traveltime data of more than 13 000 local earthquakes recorded by the Instituto Geogr´ afico Nacional (IGN, Spain) in the period from 2011 July to 2012 September. The velocity models were performed using the LOTOS code for iterative passive source tomography. The results of inversion were thoroughly verified using different resolution and robustness tests. The results reveal that the majority of the onshore area of El Hierro is associated with a high-velocity anomaly observed down to 10–12-km depth. This anomaly is interpreted as the accumulation of solid igneous rocks erupted during the last 1 Myr and intrusive magmatic bodies. Below this high-velocity pattern, we observe a low-velocity anomaly, interpreted as a batch of magma coming from the mantle located beneath El Hierro. The boundary between the low- and highvelocityanomaliesismarkedbyaprominentseismicitycluster,thoughttorepresentanomalous stresses due to the interaction of the batch of magma with crust material. The areas of recent eruptions, Orchilla and La Restinga, are associated with low-velocity anomalies surrounding the main high-velocity block. These eruptions took place around the island where the crust is much weaker than the onshore area and where the melted material cannot penetrate. These results put constraints on the geological model that could explain the origin of the volcanism in oceanic islands, such as in the Canaries, which is not yet clearly understood.

Ecology of fouling assemblages associated with mangrove's roots: An artificial substrate for manipulative experiments

Several of the most influential studies in marine ecology are based on results obtained from experiments using units of artificial habitats. However, there are few studies that have measured the effectiveness of those experimental substrates as surrogates of natural ones, in terms of reflecting natural patterns of colonization and development of the natural assemblages. Such considerations are necessary to extrapolate the described patterns and processes in artificial habitats to natural communities. This situation is particularly noticeable in ecological studies dealing with the identification of process that sustain the high levels of species diversity reported for epibiont communities that grow on the roots of Rizophora mangle in the Caribbean Sea. That is, no study has demonstrated the validity of artificial substrate as surrogate of mangrove roots. Consequently, in this study we tested whether wooden sticks can be used as surrogates for natural prop roots. Furthermore, and in order to propose possible mechanisms explaining the observed patterns, we also tested whether differences in epibiotic assemblages on natural mangrove prop roots were due primarily to intrinsic (biological) differences among roots. The experiment was conducted in four randomly chosen localities of La Restinga National Park, Venezuela, to test for the generality of the observed outcomes. We used two types of substrates: broomsticks as artificial mangrove roots (AMR) and natural mangrove roots (NMR) denuded from epibionts. We recorded the presence and estimated the abundance of sessile species growing on the experimental treatments after 30, 130 and 200days. No significant differences in species richness between the two substrates at any locality and at any time were detected. However, the effect of the substrate on the composition and abundance of species varied among localities and increased over time. Multivariate dispersion was not different between substrates, indicating that intrinsic biological characteristics of prop roots are not responsible for the observed differences among neighboring roots. Despite spatial differences at the scale of localities, most of the species recorded in this study colonized both types of substrates, although some species were more abundant over AMR (e.g. cirripeds, bryozoans), while others were more abundant on NMR (e.g. oyster, algae). Typical mangrove sponges and tunicates colonized similarly both types of substrates. Results obtained in this work suggest that broomsticks are appropriate surrogates of mangrove roots to experimentally evaluate processes associated with species diversity, but should not be used to evaluate processes that affect the abundance and structure of epibiont assemblages.

Magma displacements under insular volcanic fields, applications to eruption forecasting: El Hierro, Canary Islands, 2011-2013

Significant deformations, followed by increased seismicity detected since 2011 July at El Hierro, Canary Islands, Spain, prompted the deployment of additional monitoring equipment. The climax of this unrest was a submarine eruption first detected on 2011 October 10, and located at about 2 km SW of La Restinga, southernmost village of El Hierro Island. The eruption ceased on 2012 March 5, after the volcanic tremor signals persistently weakened through 2012 February. However, the seismic activity did not end with the eruption, as several other seismic crises followed. The seismic episodes presented a characteristic pattern: over a few days the number and magnitude of seismic event increased persistently, culminating in seismic events severe enough to be felt all over the island. Those crises occurred in 2011 November, 2012 June and September, 2012 December to 2013 January and in 2013 March–April. In all cases the seismic unrest was preceded by significant deformations measured on the island's surface that continued during the whole episode. Analysis of the available GPS and seismic data suggests that several magma displacement processes occurred at depth from the beginning of the unrest. The first main magma movement or ‘injection’ culminated with the 2011 October submarine eruption. A model combining the geometry of the magma injection process and the variations in seismic energy release has allowed successful forecasting of the new-vent opening.

Primer registro de Favorinus auritulus (Mollusca: Facelinidae) para Venezuela

Favorinus auritulus E. Marcus, 1955 is recorded for the first time in Venezuela. Specimens were found next of other mollusks eggs species on patches of Thalassia testudinum seagrass in the lagoon La Restinga, Margarita island Venezuela. F. auritulus has been previously recorded in USA (Florida), Bermuda, Bahamas, Cuba (Pinar del Río), Jamaica, Puerto Rico, Antigua, Trinidad y Tobago (Tobago), Curazao and Brazil.

Bathymetry of a new-born submarine volcano: El Hierro. Canary Islands

We present here a bathymetric map of a new underwater volcano which began its growth on 10 October 2011 to the south of El Hierro Island (Canary Is., Spain). The map scale is 1:25,000 and the map covers 210.9 sq. km. In July 2011, the seismic monitoring network of Spanish National Geographic Institute (IGN), began to detect an increase in low-intensity earthquakes around El Hierro Island along with ground deformation. This seismic crisis culminated on 10th October with a submarine eruption 2 km south of the small port of La Restinga, and lasted until March 2012 when IGN determined the end of the eruption process. After eight surveys monitoring the morphological and bathymetric evolution during the eruptive phase that ended in March 2012, Spanish Oceanographic Institute and the Hydrographic Institute of the Navy, carried out a survey from the 6th to the 8th of December 2012 to map the bathymetric and morphologic situation after the 2011–2012 eruptive period. The map presented here is based on full seafloor coverage by multibeam swath data echosounder carried out when the submarine volcano was in a quiet phase, using a grid mesh size of 12 × 12 meters.

Precursory diffuse CO2 and H2S emission signatures of the 2011–2012 El Hierro submarine eruption, Canary Islands

On October 12, 2011, a submarine eruption began 2 km off the coast of La Restinga, south of El Hierro Island. CO2 and H2S soil efflux were continuously measured during the period of volcanic unrest by using the accumulation chamber method at two different geochemical stations, HIE01 and HIE07. Recorded CO2 and H2S effluxes showed precursory signals that preceded the submarine eruption. Beginning in late August, the CO2 efflux time series started increasing at a relatively constant rate over one month, reaching a maximum of 19 gm−2d−1 one week before the onset of the submarine volcanic eruption. The H2S efflux time series at HIE07 showed a pulse in H2S emission just one day before the initiation of the submarine eruption, reaching peak values of 42 mg m−2 d−1, 10 times the average H2S efflux recorded during the observation period. Since CO2 and H2S effluxes are strongly influenced by external factors, we applied a multiple regression analysis to remove their contribution. A statistical analysis showed that the long‐term trend of the filtered data is well correlated with the seismic energy. We find that these geochemical stations are important monitoring sites for evaluating the volcanic activity of El Hierro and that they demonstrate the potential of applying continuous monitoring of soil CO2 and H2S efflux to improve and optimize the detection of early warning signals of future volcanic unrest episodes at El Hierro. Continuous diffuse degassing studies would likely prove useful for monitoring other volcanoes during unrest episodes.