Integrated Study Of Dinoflagellate Diversity In The Gulf of Naples

Dinoflagellates are a diverse lineage of protists known as an essential component of marine planktonic communities. To study their seasonal diversity at the LTER-MC station in the Gulf of Naples, I used high throughput sequencing (HTS) metabarcoding of the V4 region in the 18S rDNA. To taxonomically identify the metabarcode sequences, I established a database, called DinoREF, of taxonomically verified and nomenclaturally updated 18S reference barcodes with associated metadata. The reference sequences were organised into Superclades based on phylogenetics and higher taxonomic treatment. DinoREF contains 1,671 sequences for 422 species and covering 22% of the described species. The database revealed that the V4 region alone cannot discriminate between some morphologically and genetically distinct species or genera. Moreover, many species and genera were collapsed together when clustered into 98% similarity OTUs. For the metabarcoding, dinoflagellate HTS V4 reads were gathered from 48 environmental DNA samples taken over three years at LTER-MC. Results of a-taxonomic cluster analysis showed three principal seasonal clusters, one with winter samples (16% of reads), one with mainly spring-summer samples (62%) and one with late summer-autumn samples (22%). Sorting reads into ribotypes and assigning them with DinoREF to taxa showed that reads belonging to the Gyrodinium, Gymnodiniales and Gonyaulacales Superclades were the most abundant. Winter samples were characterised by specific taxa thriving only in cold season. Results revealed 85 new records and detected 26 potentially toxic species for the Gulf of Naples. Many dinoflagellate genera such as Tripos are underrepresented in DinoREF because many species cannot be cultured. I applied single cell imaging, PCR and sequencing to gather 18S and 28S for 22 Tripos species. Using 18S V4 region as barcode I assessed the seasonal abundances of these species. Some were common all year whereas others showed distinct seasonality, mainly occurring in winter

Continuous Monitoring of High‐Rise Buildings Using Seismic Interferometry

The linear seismic response of a building is commonly extracted from ambient vibration measurements. Seismic deconvolution interferometry performed on ambient vibrations can be used to estimate the dynamic characteristics of a building, such as its shear-wave velocity and its damping. The continuous nature of the ambient vibrations allows us to measure these parameters repeatedly and to observe their temporal variations. We used 2 weeks of ambient vibrations, recorded by 36 accelerometers that were installed in the Green Building at the Massachusetts Institute of Technology campus, to monitor the shear wavespeed and the apparent attenuation factor of the building. Because of the low strain of the ambient vibrations, we observed small speed changes followed by recoveries. We showed that measuring the velocity variations for the deconvolution functions, filtered around the fundamental-mode frequency, is equivalent to measuring the wandering of the fundamental frequency in the raw ambient vibration data. By comparing these results with local weather parameters, we showed that the air humidity is the dominating factor in the velocity variations of the waves in the Green Building, as well as the main force behind the wandering of the fundamental mode. The one-day periodic variations are affected by both the temperature and the humidity. The apparent attenuation, measured as the exponential decay of the fundamental-mode waveforms, is strongly biased due to the amplitude of the raw vibrations and shows a more complex behavior with respect to the weather measurements. We have also detected normal-mode nonlinear interaction for the Green Building, likely due to heterogeneity or anisotropy of its structure. We found that the temporal behavior of the frequency singlets may be used for monitoring.Royal Dutch-Shell Group (through MIT Energy Initiative)National Science Foundation (U. S.) (Grant Grant EAR-1415907

Azimuthal Anisotropy at Valhall: the Helmholtz Equation Approach

International audienceWe used 6 hours of continuous vertical records from 2320 sensors of the Valhall Life of Fields Seismic network to compute 2 690 040 cross-correlation functions between the full set of sensor pair combinations. We applied the 'Helmholtz tomography' approach combined with the ambient noise correlation method to track the wave front across the network with every station considered as a virtual source. The gradient of the interpolated phase travel time gives us an estimate of the local phase speed and of the direction of wave propagation. By combining the individual measurements for every station, we estimated the distribution of Scholte's wave phase speeds with respect to azimuth. The observed cosine pattern indicates the presence of azimuthal anisotropy. The elliptic shape of the fast anisotropy direction is consistent with results of previous shear wave splitting studies and reflects the strong seafloor subsidence due to the hydrocarbon reservoir depletion at depth and is in good agreement with geomechanical modeling

Temporal Seismic Velocity Changes During the 2020 Rapid Inflation at Mt. Þorbjörn-Svartsengi, Iceland, Using Seismic Ambient Noise

Publisher Copyright: © 2021. The Authors.Repeated periods of inflation-deflation in the vicinity of Mt. Þorbjörn-Svartsengi, SW-Iceland, were detected in January–July, 2020. We used seismic ambient noise and interferometry to characterize temporal variations of seismic velocities (dv/v, %). This is the first time in Iceland that dv/v variations are monitored in near real-time during volcanic unrest. The seismic station closest to the inflation source center (∼1 km) showed the largest velocity drop (∼1%). Different frequency range measurements, from 0.1 to 2 Hz, show dv/v variations, which we interpret in terms of varying depth sensitivity. The dv/v correlates with deformation measurements (GPS, InSAR), over the unrest period, indicating sensitivity to similar crustal processes. We interpret the velocity drop to be caused by crack opening triggered by intrusive magmatic activity. We conclude that single-station cross-component analyses provide the most robust solutions for early detection of magmatic activity.Peer reviewe

Organisational Response to the 2007 Ruapehu Crater Lake Dam-Break Lahar in New Zealand: Use of Communication in Creating an Effective Response

When Mt. Ruapehu erupted in 1995–1996 in New Zealand, a tephra barrier was created alongside Crater Lake on the top of Mt. Ruapehu. This barrier acted as a dam, with Crater Lake rising behind it over time. In 2007 the lake breached the dam and a lahar occurred down the Whangaehu Valley and across the volcano’s broad alluvial ring-plain. Given the lahar history from Ruapehu, the risk from the 2007 event was identified beforehand and steps taken to reduce the risks to life and infrastructure. An early warning system was set up to notify when the dam had broken and the lahar had occurred. In combination with the warning system, physical works to mitigate the risk were put in place. A planning group was also formed and emergency management plans were put in place to respond to the risk. To assess the effectiveness of planning for and responding to the lahar, semi-structured interviews were undertaken with personnel from key organisations both before and after the lahar event. This chapter discusses the findings from the interviews in the context of communication, and highlights how good communication contributed to an effective emergency management response. As the potential for a lahar was identifiable, approximately 10 years of lead-up time was available to install warning system hardware, implement physical mitigation measures, create emergency management plans, and practice exercises for the lahar. The planning and exercising developed effective internal communications, engendered relationships, and moved individuals towards a shared mental model of how a respond to the event. Consequently, the response played out largely as planned with only minor communication issues occurring on the day of the lahar. The minor communication issues were due to strong personal connections leading to at least one incidence where the plan was bypassed. Communication levels during the lahar event itself were also different from that experienced in exercises, and in some instances communication was seen to increase almost three-fold. This increase in level of communication, led to some difficulty in getting through to the main Incident Control Point. A final thought regarding public communication prior to the event was that more effort could have been given to developing and integrating public information about the lahar, to allow for ease of understanding about the event and integration of information across agencies.</p

Rapid response to the M_w 4.9 earthquake of November 11, 2019 in Le Teil, Lower Rhône Valley, France

On November 11, 2019, a Mw 4.9 earthquake hit the region close to Montelimar (lower Rhône Valley, France), on the eastern margin of the Massif Central close to the external part of the Alps. Occuring in a moderate seismicity area, this earthquake is remarkable for its very shallow focal depth (between 1 and 3 km), its magnitude, and the moderate to large damages it produced in several villages. InSAR interferograms indicated a shallow rupture about 4 km long reaching the surface and the reactivation of the ancient NE-SW La Rouviere normal fault in reverse faulting in agreement with the present-day E-W compressional tectonics. The peculiarity of this earthquake together with a poor coverage of the epicentral region by permanent seismological and geodetic stations triggered the mobilisation of the French post-seismic unit and the broad French scientific community from various institutions, with the deployment of geophysical instruments (seismological and geodesic stations), geological field surveys, and field evaluation of the intensity of the earthquake. Within 7 days after the mainshock, 47 seismological stations were deployed in the epicentral area to improve the Le Teil aftershocks locations relative to the French permanent seismological network (RESIF), monitor the temporal and spatial evolution of microearthquakes close to the fault plane and temporal evolution of the seismic response of 3 damaged historical buildings, and to study suspected site effects and their influence in the distribution of seismic damage. This seismological dataset, completed by data owned by different institutions, was integrated in a homogeneous archive and distributed through FDSN web services by the RESIF data center. This dataset, together with observations of surface rupture evidences, geologic, geodetic and satellite data, will help to unravel the causes and rupture mechanism of this earthquake, and contribute to account in seismic hazard assessment for earthquakes along the major regional Cévenne fault system in a context of present-day compressional tectonics

Single station Monitoring of Volcanoes Using Seismic ambient noise

Seismic ambient noise cross correlation is increasingly used to monitor volcanic activity. However, this method is usually limited to volcanoes equipped with large and dense networks of broadband stations. The single station approach may provide a powerful and reliable alternative to the classical “cross-stations” approach when measuring variation of seismic velocities. We implemented it on the Piton de la Fournaise in Reunion Island, a very active volcano with a remarkable multi-disciplinary continuous monitoring. Over the past decade, this volcano was increasingly studied using the traditional cross-correlation technique and therefore represents a unique laboratory to validate our approach. Our results, tested on stations located up to 3.5 km from the eruptive site, performed as well as the classical approach to detect the volcanic eruption in the 1-2 Hz frequency band. This opens new perspectives to successfully forecast volcanic activity at volcanoes equipped with a single 3-component seismometer

Haslea silbo, a novel cosmopolitan species of blue diatoms

Specimens of a new species of blue diatoms from the genus Haslea Simonsen were discovered in geographically distant sampling sites, first in the Canary Archipelago, then North Carolina, Gulf of Naples, the Croatian South Adriatic Sea, and Turkish coast of the Eastern Mediterranean Sea. An exhaustive characterization of these specimens, using a combined morphological and genomic approach led to the conclusion that they belong to a single new to science cosmopolitan species, Haslea silbo sp. nov. A preliminary characterization of its blue pigment shows similarities to marennine produced by Haslea ostrearia, as evidenced by UV–visible spectrophotometry and Raman spectrome-try. Life cycle stages including auxosporulation were also observed, providing data on the cardinal points of this species. For the two most geographically distant populations (North Carolina and East Mediterranean), complete mitochondrial and plastid genomes were sequenced. The mitogenomes of both strains share a rare atp6 pseudogene, but the number, nature, and positions of the group II introns inside its cox1 gene differ between the two populations. There are also two pairs of genes fused in single ORFs. The plastid genomes are characterized by large regions of recombination with plasmid DNA, which are in both cases located between the ycf35 and psbA genes, but whose content differs between the strains. The two sequenced strains hosts three plasmids coding for putative serine recombinase protein whose sequences are compared, and four out of six of these plasmids were highly conserved