Low reproductive success for copepods during a bloom of the non‐aldehyde‐producing diatom Cerataulina pelagica in the North Adriatic Sea     

Adrianna Ianora  Raffaella Casotti  Mauro Bastianini  Christophe Brunet  Giuliana D’Ippolito  Francesco Acri  Angelo Fontana  Adele Cutignano  Jefferson T. Turner  Antonio Miralto 《Marine Ecology》2008,29(3):399-410

Egg production rates and/or hatching success in the copepods Acartia clausi, Calanus helgolandicus and Temora longicornis were negatively affected by a late spring (May–June 2003) phytoplankton bloom in the North Adriatic Sea, dominated mainly by the large diatom Cerataulina pelagica. Highest total concentrations of 3.3·10⁴ cells·ml^?1 were located in the vicinity of the Po River, which also corresponded to the area where the highest numbers of phaeophorbides were measured (0.779, 0.528 and 0.419 μg·l^?1, respectively, compared to an average of the remaining stations of 0.183 ± 0.049 SD), suggesting some grazing on the bloom. Phytoplankton biomass in terms of carbon was dominated by diatoms, representing on average 42% of total phytoplankton carbon and more than 80% at several stations. Cerataulina pelagica, Cyclotella spp., Chaetoceros spp. and small unidentified centric diatoms dominated the diatom community numerically but C. pelagica was by far the dominant diatom in terms of carbon due to its large cell size. This species represented more than 60% of the diatom biomass at nine of the 14 stations sampled, and was absent only at one station, which was the most offshore station sampled during the cruise. Although polyunsaturated aldehydes (PUAs) were not detected, other oxylipins which are hydroxy and keto derivatives of eicosapentaenoic and docosahexaenoic acids that affect copepod reproduction were found in these samples. Hence, we can attribute the negative impact of diatoms not only to PUAs, as previously believed, but also to these compounds. This is the first direct evidence of the presence of oxylipins other than PUAs in marine blooms dominated by diatoms.  相似文献   

Fluid flow and pore pressure development throughout the evolution of a trough mouth fan,western Barents Sea     

Jaume Llopart  Roger Urgeles  Carl Fredrik Forsberg  Angelo Camerlenghi  Maarten Vanneste  Michele Rebesco  Renata Giulia Lucchi  Denise Christina Rüther  Hendrik Lantzsch 《Basin Research》2019,31(3):487-513

Using a combination of geophysical and geotechnical data from Storfjorden Trough Mouth Fan off southern Svalbard, we investigate the hydrogeology of the continental margin and how this is affected by Quaternary glacial advances and retreats over the continental shelf. The geotechnical results show that plumites, deposited during the deglaciation, have high porosities, permeabilities and compressibilities with respect to glacigenic debris flows and tills. These results together with margin stratigraphic models obtained from seismic reflection data were used as input for numerical finite element models to understand focusing of interstitial fluids on glaciated continental margins. The modelled evolution of the Storfjorden TMF shows that tills formed on the shelf following the onset of glacial sedimentation (ca. 1.5 Ma) acted as aquitards and therefore played a significant role in decreasing the vertical fluid flow towards the sea floor and diverting it towards the slope. The model shows that high overpressure ratios (up to λ ca. 0.6) developed below the shelf edge and on the middle slope. A more detailed model for the last 220 kyrs accounting for ice loading during glacial maxima shows that the formation of these aquitards on the shelf focused fluid flow towards the most permeable plumite sediments on the slope. The less permeable glacigenic debris flows that were deposited during glacial maxima on the slope hinder fluid evacuation from plumites allowing high overpressure ratios (up to λ ca. 0.7) to develop in the shallowest plumite layers. These high overpressures likely persist to the Present and are a critical precondition for submarine slope failure.  相似文献   

Geological mapping reveals the role of Early Jurassic rift architecture in the dispersal of calciturbidites: New insights from the Central and Northern Apennines     

Angelo Cipriani  Martina Caratelli  Massimo Santantonio 《Basin Research》2020,32(6):1485-1509

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Community structure of infaunal macrobenthos around vestimentiferan thickets at the San Clemente cold seep,NE Pacific     

Angelo F. Bernardino  Craig. R. Smith 《Marine Ecology》2010,31(4):608-621

The San Clemente cold seep lies within 100–200 km of other reducing habitats in the NE Pacific, offering an opportunity to compare diversity and species overlap among reducing habitats (i.e. whale‐, kelp‐, and wood‐falls) at similar depths within a single region. Video observations from the research submersible Alvin at the San Clemente seep (1800 m depth) indicated clumps (‘thickets’) of vestimentiferans distributed as meter‐scale patches interspersed with vesicomyid clam beds and black sediments. Sediment‐core samples were collected at distances of 0 to 80–200 m along randomly oriented transects radiating outward from vestimentiferan thickets to evaluate changes in macrofaunal community structure from thickets into the background community. Macrofaunal abundance was elevated at distances of 0–1 m compared to 80–200 m (i.e. the ‘background’ community). The tube‐building frenulate worms Siboglinum spp., along with peracarid crustaceans, dominated sediments within 1 m of vestimentiferan thickets. Species diversity was depressed within 1 m of thickets but with high rates of species accumulation, suggesting that seep sites greatly increase sediment heterogeneity and facilitate colonization by non‐background macrofaunal species. Stable isotope data indicate chemosynthetic nutrition for some dominant macrofaunal species within 1 m of tubeworm thickets. The macrofaunal community near vestimentiferan thickets in San Clemente seep contains intermediate levels of species richness and diversity compared to other deep‐sea seep areas in the northeast Pacific. There was low species overlap between the San Clemente seep macrofauna and communities in reducing habitats near wood‐, whale‐, and kelp‐falls at similar depths within the region, suggesting that seeps harbor a distinct infaunal community.  相似文献   

A non‐collisional,accretionary Sveconorwegian orogen – Comment     

Charlotte Möller  Bernard Bingen  Jenny Andersson  Michael B. Stephens  Giulio Viola  Anders Scherstén 《地学学报》2013,25(2):165-168

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Observations of sea breeze events in Rome and the surrounding area by a network of Doppler sodars     

G. Mastrantonio  A. P. Viola  S. Argentini  G. Fiocco  L. Giannini  L. Rossini  G. Abbate  R. Ocone  M. Casonato 《Boundary-Layer Meteorology》1994,71(1-2):67-80

In the period June–July 1992, four Doppler sodars were operated simultaneously in Rome and the surrounding area. The data have been used to investigate the contributions from sea breeze events to the local low-level circulation. Three days in which synoptic-scale pressure gradients were weak have been selected. A number of characteristics of the sea breeze are examined including the onset and cessation of the phenomenon, the behavior of the wind speed, and the depth of the density flow. The time propagation of the events and the influence of orography are obtained from a comparison between the data at different sites. The low-level circulation in the early morning is associated with the land breeze and appears to be enhanced by a mountain wind from the surrounding hills. The observed behavior of the vertical velocity field associated with the sea breeze is consistent with model predictions.  相似文献   

Geochronological constraints on the evolution of the Periadriatic Fault System (Alps)     

Wolfgang Müller  Giacomo Prosser  Neil S. Mancktelow  Igor M. Villa  Simon P. Kelley  Giulio Viola  Felix Oberli 《International Journal of Earth Sciences》2001,90(3):623-653

Fault rocks from various segments of the Periadriatic fault system (PAF; Alps) have been directly dated using texturally controlled Rb-Sr microsampling dating applied to mylonites, and both stepwise-heating and laser-ablation ⁴⁰Ar/³⁹Ar dating applied to pseudotachylytes. The new fault ages place better constraints on tectonic models proposed for the PAF, particularly in its central sector. Along the North Giudicarie fault, Oligocene (E)SE-directed thrusting (29-32 Ma) is currently best explained as accommodation across a cogenetic restraining bend within the Oligocene dextral Tonale-Pustertal fault system. In this case, the limited jump in metamorphic grade observed across the North Giudicarie fault restricts the dextral displacement along the kinematically linked Tonale fault to ~30 km. Dextral displacement between the Tonale and Pustertal faults cannot be transferred via the Peio fault because of both Late Cretaceous fault ages (74-67 Ma) and sinistral transtensive fault kinematics. In combination with other pseudotachylyte ages (62-58 Ma), widespread Late Cretaceous-Paleocene extension is established within the Austroalpine unit, coeval with sedimentation of Gosau Group sediments. Early Miocene pseudotachylyte ages (22-16 Ma) from the Tonale, Pustertal, Jaufen and Passeier faults argue for a period of enhanced fault activity contemporaneous with lateral extrusion of the Eastern Alps. This event coincides with exhumation of the Penninic units and contemporaneous sedimentation within fault-bound basins.  相似文献   

The DAV and Periadriatic fault systems in the Eastern Alps south of the Tauern window     

Neil S. Mancktelow  Daniel F. Stöckli  Balz Grollimund  Wolfgang Müller  Bernhard Fügenschuh  Giulio Viola  Diane Seward  Igor M. Villa 《International Journal of Earth Sciences》2001,90(3):593-622

Alpine deformation of Austroalpine units south of the Tauern window is dominated by two kinematic regimes. Prior to intrusion of the main Periadriatic plutons at ~30 Ma, the shear sense was sinistral in the current orientation, with a minor north-side-up component. Sinistral shearing locally overprints contact metamorphic porphyroblasts and early Periadriatic dykes. Direct Rb-Sr dating of microsampled synkinematic muscovite gave ages in the range 33-30 Ma, whereas pseudotachylyte locally crosscutting the mylonitic foliation gave an interpreted ⁴⁰Ar-³⁹Ar age of ~46 Ma. The transition from sinistral to dextral (transpressive) kinematics related to the Periadriatic fault occurred rapidly, between solidification of the earlier dykes and of the main plutons. Subsequent brittle-ductile to brittle faults are compatible with N-S to NNW-SSE shortening and orogen-parallel extension. Antithetic Riedel shears are distinguished from the previous sinistral fabric by their fine-grained quartz microstructures, with local pseudotachylyte formation. One such pseudotachylyte from Speikboden gave a ⁴⁰Ar-³⁹Ar age of 20 Ma, consistent with pseudotachylyte ages related to the Periadriatic fault. The magnitude of dextral offset on the Periadriatic fault cannot be directly estimated. However, the jump in zircon and apatite fission-track ages establishes that the relative vertical displacement was ~4-5 km since 24 Ma, and that movement continued until at least 13 Ma.  相似文献   

Geochemistry of eocene calc-alkaline volcanic rocks from the Kastamonu area,Northern Turkey   总被引：294，自引：3，他引：294  

Angelo Peccerillo  S. R. Taylor 《Contributions to Mineralogy and Petrology》1976,58(1):63-81

Analytical data for Sr, Rb, Cs, Ba, Pb, rare earth elements, Y, Th, U, Zr, Hf, Sn, Nb, Mo, Ni, Co, V, Cr, Sc, Cu and major elements are reported for eocene volcanic rocks cropping out in the Kastamonu area, Pontic chain of Northern Turkey. SiO₂% versus K₂O% relationship shows that the analyzed samples belong to two major groups: the basaltic andesitic and the andesitic ones. High-K basaltic andesites and low-K andesites occur too. Although emplaced on continental type basement (the North Anatolian Crystalline Swell), the Pontic eocene volcanics show elemental abundances closely comparable with typical island arc calc-alkaline suites, e.g. low SiO₂% range, low to moderate K₂O% and large cations (Cs, Rb, Sr, Ba, Pb) contents and REE patterns with fractionated light and almost flat heavy REE patterns. REE and highly charged cations (Th, U, Hf, Sn, Zr) are slightly higher than typical calc-alkaline values. Ferromagnesian elements show variable values. Within the basaltic andesite group the increase of K%, large cations, REE, La/Yb ratio and high valency cations and the decrease of ferromagnesian element abundances with increasing SiO₂% content indicate that the rock types making up this group developed by crystalliquid fractionation of olivine and clinopyroxene from a basic parent magma. Trace element concentration suggest that the andesite group was not derived by crystal-liquid fractionation processes from the basaltic andesites, but could represent a distinct group of rocks derived from a different parent magma.  相似文献   

Dynamics of a particle in a gravitational field of a homogeneous annulus disk   总被引：1，自引：0，他引：1  

Angelo Alberti  Claudio Vidal 《Celestial Mechanics and Dynamical Astronomy》2007,98(2):75-93

We formulate the problem of an infinitesimal particle moving in the space under the influence of the gravitational force induced by a homogeneous annulus disk fixed on a plane. We compute using different coordinates and in terms of an elliptic integral the potential associated to this problem. Also we study the symmetries of the associated potential. After that, we look at the dynamics in some particular cases, namely: in the line perpendicular to the plane that contains the annulus disk and passes through the center of the ring and on the plane that contains the massive annulus.   相似文献