Ecological Differences in the Distribution of two Tethya (Porifera, Demospongiae) Species Coexisting in a Mediterranean Coastal Lagoon

Abstract. In the Sicilian lagoon Stagnone di Marsala, Tethya aurantium and T. citrina show different ecological distributions, although some overlapping occurs. The first species reaches its highest density where linear currents are maximal, and in this habitat it is particularly frequent on Posidonia oceanica rhizomes. The second species is more abundant in still water locations and is equally common on Posidonia rhizomes and on calcareous concretions. Such distributions can be related to water movement, Posidonia shoot density, and associated factors such as sedimentation and food availability. These observations are consistent with an adaptive interpretation of the morphofunctional features distinguishing the two species.     

The structure of the Campanian Plain and the activity of the Neapolitan volcanoes (Italy)

The central Campanian Plain is dominated by the structural depression of Acerra whose origin is tectonic, but may have been enlarged and further depressed after the eruption of the Campanian Ignimbrite (42-25 ka). The deposits of the Campanian Ignimbrite are possibly the results of multiple eruptions with huge pyroclastic deposits that covered all the Campanian Plain.The more recent activity of Vesuvius, Campi Flegrei and Procida occurred on the borders of Acerra depression and resulted from a reactivation of regional faults after the Campanian Ignimbrite cycle. The activity of Vesuvius produced the building of a stratovolcano mostly by effusive and plinian explosive eruptions. The Campi Flegrei area, on the contrary, was dominated by the eruption of the Neapolitan Yellow Tuff at 12 ka that produced a caldera collapse of the Gulf of Pozzuoli. The caldera formation controlled the emplacement of the recent activity of Campi Flegrei and the new volcanoes were formed only within the caldera or along its rim.     

An experimental study of magnesite dissolution rates at neutral to alkaline conditions and 150 and 200 °C as a function of pH, total dissolved carbonate concentration, and chemical affinity

Steady-state magnesite dissolution rates were measured in mixed-flow reactors at 150 and 200 °C and 4.6 < pH < 8.4, as a function of ionic strength (0.001 M ? I ? 1 M), total dissolved carbonate concentration (10⁻⁴ M < ΣCO₂ < 0.1 M), and distance from equilibrium. Rates were found to increase with increasing ionic strength, but decrease with increasing temperature from 150 to 200 °C, pH, and aqueous CO₃²⁻ activity. Measured rates were interpreted using the surface complexation model developed by Pokrovsky et al. (1999a) in conjunction with transition state theory (Eyring, 1935). Within this formalism, magnesite dissolution rates are found to be consistent with

     

Measuring the north–south coseismic displacement component with high‐resolution multi‐aperture InSAR

Earthquake source inversions based on space‐borne Synthetic Aperture Radar interferometry (InSAR) are used extensively. Typically, however, only the line‐of‐sight (LoS) surface displacement component is measured, which is mainly sensitive to the vertical and E–W deformations, although well‐established methods also exist to estimate the flight‐path component, which is highly sensitive to the N–S displacement. With high‐resolution sensors, these techniques are particularly appealing, because accuracies in the order of 3 cm can be achieved, while retaining spatial resolutions between 45 m and a few km, depending on the required level of filtering. We discuss the application to COSMO‐SkyMed SAR imagery of the Spectral Diversity or Multi Aperture Interferometry technique, presenting the first SAR flight‐path displacement field associated with the Mw 6.3, 2009 L'Aquila event (central Apennines). Finally, we observe and characterize a previously unknown misregistration pattern.     

Ensemble smoothing of land subsidence measurements for reservoir geomechanical characterization

Geomechanical models are often used to predict the impact on land surface of fluid withdrawal from deep reservoirs, as well as investigating measures for mitigation. The ability to accurately simulate surface displacements, however, is often impaired by limited information on the geomechanical parameters characterizing the geological formations of interest. In this study, we employ an ensemble smoother, a data assimilation algorithm, to provide improved estimates of reservoir parameters through assimilation of measurements of both horizontal and vertical surface displacement into geomechanical model results. The method leverages the demonstrated potential of remote sensing techniques developed in the last decade to provide accurate displacement data for large areas of the land surface. For evaluation purposes, the methodology is applied to the case of a disk‐shaped reservoir embedded in a homogeneous, isotropic, and linearly elastic half space, subject to a uniform change in fluid pressure. Multiple sources of uncertainty are investigated, including the radius, R, the thickness, h, and the depth, c, of the reservoir; the pore pressure change, Δp; porous medium's vertical uniaxial compressibility, c_M, and Poisson's ratio, ν, and the ratio, s, between the compressibilities of the medium during loading and unloading cycles. Results from all simulations show that the ensemble smoother has the capability to effectively reduce the uncertainty associated with those parameters to which the variability and the spatial distribution of land surface displacements are most sensitive, namely, R, c, c_M, and s. These analyses demonstrate that the estimation of these parameters values depends on the number of measurements assimilated and the error assigned to the measurement values. Copyright © 2014 John Wiley & Sons, Ltd.     

Late Pleistocene to Holocene record of changing uplift rates in southern Calabria and northeastern Sicily (southern Italy, Central Mediterranean Sea)

A combination of published and new radiometric dates on uplifted Holocene fossil beaches from northeastern Sicily and southern Calabria (southern Italy) is compared with the altitude of the inner margin of the Last Interglacial (LIg) (Late Pleistocene, 124 ka) and older marine terraces in order to gain a regional-scale outline of uplift rates and their temporal changes in a region which is one of the fastest uplifting sectors of the Central Mediterranean Sea. Late Holocene radiocarbon dates from Ioppolo (southern Calabria) and Ganzirri (northeast Sicily), two newly discovered sites are here presented for the first time. The Holocene uplift rates are highest at St. Alessio and Taormina in eastern Sicily (2.4 mm/y) and at Scilla in southwestern Calabria (2.1 mm/y), two sites located across the Messina Straits and which separate the island of Sicily from mainland Italy. Uplift rates decrease towards the south and north from this centre of uplift. Late Holocene uplift rates show an apparent increase of between 64 and 124% when compared with the longer-term uplift rates calculated from the LIg highstand terraces. Furthermore, we discovered that the locations of fastest Late Pleistocene and Late Holocene uplift rates spatially coincide. To what extent the Holocene increase in uplift rates results from incomplete elastic strain release along the major extensional faults which frame the seismotectonic of the area, or indicate a true change in regional tectonic processes, is not resolved. Nonetheless, the heterogeneity of uplift, with a well-defined centre that crosses the Messina Straits, and its persistence at different time-scales indicates a tight connection between wider regional processes and fault-related displacement in controlling crustal instability in this area.     

A merger tree with microsolar mass resolution: application to γ-ray emission from subhalo population

Observations of the southern Cepheid ℓ Car to yield the mean angular diameter and angular pulsation amplitude have been made with the Sydney University Stellar Interferometer at a wavelength of 696 nm. The resulting mean limb-darkened angular diameter is 2.990 ± 0.017 mas (i.e. ± 0.6 per cent) with a maximum-to-minimum amplitude of 0.560 ± 0.018 mas corresponding to 18.7 ± 0.6 per cent in the mean stellar diameter. Careful attention has been paid to uncertainties, including those in measurements, in the adopted calibrator angular diameters, in the projected values of visibility squared at zero baseline, and to systematic effects. No evidence was found for a circumstellar envelope at 696 nm. The interferometric results have been combined with radial displacements of the stellar atmosphere derived from selected radial velocity data taken from the literature to determine the distance and mean diameter of ℓ Car. The distance is determined to be 525 ± 26 pc and the mean radius  169 ± 8 R_⊙  . Comparison with published values for the distance and mean radius shows excellent agreement, particularly when a common scaling factor from observed radial velocity to pulsation velocity of the stellar atmosphere (the p -factor) is used.     

2-Gyr Simulation of the Oort-Cloud Formation. I. Introduction on a New Model of the Outer Oort-Cloud Formation

The study of the reservoirs of small bodies in the Solar System can help us to refine our theory of the origin and evolution of the whole planetary system we live in. In this contribution, we introduce a simulation of the evolution of an initial proto-planetary disc (PPD) for 2 Gyr period, in which 10,038 studied test particles (TPs), representing the disc, are perturbed by four giant planets in their current orbits and having their current masses. In addition, Galactic-tide and stellar perturbations are considered. The outer Oort cloud (OC) appears to be formed within about 0.5 Gyr. At 2 Gyr, only 0.14% of all TPs reside in the outer OC, according to our simulation. This is the largest discrepancy with the results of previous authors. The TPs in the outer OC originate from almost all regions of the PPD. Specifically, 14, 7, 29, 21, and 29% of all TPs, that are the members of the outer OC at 2 Gyr, originate in the Jupiter, Saturn, Uranus, Neptune, and Edgeworth-Kuiper-belt regions, respectively. The largest number of the TPs, 6,669 (66.4%), was ejected into the interstellar space. Besides other results, we found a dominance of high galactic inclinations of outer-OC orbits. Obviously, this is a consequence of the action of Galactic tide.     

Few Comments on the Relation Between the Initial Proto-planetary Disc Model and the Oort Cloud Formation

A fraction of small bodies from the once existing proto-planetary disc was ejected, by the giant planets, to large heliocentric distances and start to build the comet Oort cloud. Considering four models of initial proto-planetary disc, we attempt to roughly map a dependence between the initial disc’s structure and some properties of the Oort cloud. We find that it is difficult to construct the proto-planetary disc if (i) the amount of heavy chemical elements in Jupiter and Saturn is as high as currently accepted and (ii) the total mass of the minimum-mass solar nebula is assumed to be lower than $\approx0.05\,\hbox{M}_{\odot}.$ The behaviour of the Oort cloud formation does not crucially depend on the initial disc model. Some differences in its structure are obvious: since the cloud is known to be filled mainly by Uranus and Neptune, the efficiency of its formation is higher when the initial amount of particles in the Uranus-Neptune region is relatively higher. A significantly large number of Jupiter Trojans in our simulation appears, however, only in the case of the initially non-gapped disc, with the particles situated also close to the Jupiter’s orbit.     

Field study and laboratory experiments of bubble plumes in shallow seas as analogues of sub-seabed CO2 leakages

To understand the effects of increased levels of CO₂ on the marine realm, it is possible to study areas where, for natural reasons, there are emissions of CO₂ from the seabed. One of these areas is located east of Panarea Island (Aeolian Islands – Southern Tyrrhenian Sea – Italy). Here, the volcanic activity that characterizes the Aeolian archipelago causes a continuous release of CO₂ (up to 98% of the total gas) from several vents on the seafloor in shallow water. This area was studied by means of surface techniques and direct SCUBA diving surveys; the data presented refers to a field campaign performed in 2008. To collect the necessary data, some dedicated sampling and measuring techniques were developed for use in an underwater environment. The chemistry of the fluids and their influence on the water body was determined via logs and transects in the field and by gas-chromatographic and liquid-chromatographic laboratory analysis. The flux from some of the main gas vents was also measured directly underwater. Furthermore, some laboratory experiments in a two-layer stratified fluid were conducted to understand the main features of the physical interaction of a gas plume with the surrounding environment. Both field and laboratory experiments show that there is a development of a pseudo-convective cell around the rising plume with the formation of vortices that act as a physical barrier thus reducing the interaction between the plume and the surrounding water.