Estimation of spawning habitats of market squid (Doryteuthis opalescens) from field surveys of eggs off Central and Southern California     

Louis D. Zeidberg  John L. Butler  Darlene Ramon  Anthony Cossio  Kevin L. Stierhoff  Annette Henry 《Marine Ecology》2012,33(3):326-336

Like many other loliginid squid, Doryteuthis (Loligo) opalescens deposits egg cases on the ocean floor. Depending upon temperature, egg cases may persist for 5–12 weeks before the paralarvae hatch. Because of this relatively long duration and squid’s pelagic life history, egg cases provide a practical life stage to survey. During 2001–2002, squid egg beds in Monterey Bay, Carmel Bay, and around the California Channel Islands were surveyed using a remotely operated vehicle with the goal of delineating the habitat of egg beds that are spawned during active commercial fishing. Egg cases were highly aggregated and densities reached 1338 capsules m⁻². Squid eggs were significantly shallower in Central California. Egg cases occurred between 20 and 93 m around the Channel Islands, and in Central California they were between 13 and 61 m. The temperatures in both regions were similar (10–12 °C), with some eggs in Southern California found up to 14.4 °C. Ninety-five percent of eggs were found on sand, suggesting that temperature and substrate are stronger behavioral cues than depth to stimulate spawning. Suitable spawning habitat was defined by three criteria: sandy benthic substrate, temperatures between 10 and 14.4 °C, and depths between 20 and 70 m when the first two criteria hold. Additionally, within this defined area, oxygen concentration is quantified. The greatest commercial landings of market squid occur in both Central and Southern California during a time of year when water temperatures of 10–12 °C are prevalent in the 20–70 m depth range.  相似文献   

Rayleigh-Wave,Group-Velocity Tomography of the Borborema Province,NE Brazil,from Ambient Seismic Noise     

Rafaela Carreiro Dias  Jordi Julià  Martin Schimmel 《Pure and Applied Geophysics》2015,172(6):1429-1449

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Spatial and environmental analysis of an ostracod metacommunity from endorheic lakes     

Andreu Castillo-Escrivà  Luis Valls  Carlos Rochera  Antonio Camacho  Francesc Mesquita-Joanes 《Aquatic Sciences - Research Across Boundaries》2016,78(4):707-716

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Joint Audio-Magnetotelluric and Passive Seismic Imaging of the Cerdanya Basin     

A. Gabàs  A. Macau  B. Benjumea  P. Queralt  J. Ledo  S. Figueras  A. Marcuello 《Surveys in Geophysics》2016,37(5):897-921

The structure of Cerdanya Basin (north-east of Iberian Peninsula) is partly known from geological cross sections, geological maps and vintage geophysical data. However, these data do not have the necessary resolution to characterize some parts of Cerdanya Basin such as the thickness of soft soil, geometry of bedrock or geometry of geological units and associated faults. For all these reasons, the main objective of this work is to improve this deficiency carrying out a detailed study in this Neogene basin applying jointly the combination of passive seismic methods (H/V spectral ratio and seismic array) and electromagnetic methods (audio-magnetotelluric and magnetotelluric method). The passive seismic techniques provide valuable information of geometry of basement along the profile. The maximum depth is located near Alp village with a bedrock depth of 500 m. The bedrock is located in surface at both sites of profile. The Neogene sediments present a shear-wave velocity between 400 and 1000 m/s, and the bedrock basement presents a shear-wave velocity values between 1700 and 2200 m/s. These results are used as a priori information to create a 2D resistivity initial model which constraints the inversion process of electromagnetic data. We have obtained a 2D resistivity model which is characterized by (1) a heterogeneous conductivity zone (<40 Ohm m) that corresponds to shallow part of the model up to 500 m depth in the centre of the profile. These values have been associated with Quaternary and Neogene sediments formed by silts, clays, conglomerates, sandstones and gravels, and (2) a deeper resistive zone (1000–3000 Ohm m) interpreted as Palaeozoic basement (sandstones, limestones and slates at NW and conglomerates and microconglomerates at SE). The resistive zone is truncated by a discontinuity at the south-east of the profile which is interpreted as the Alp-La Tet Fault. This discontinuity is represented by a more conductive zone (600 Ohm m approx.) and is explained as a combination of fractured rock and a fluid network. The result highlights that the support between different geophysical methods is essential in producing geophysical meaningful models.  相似文献   

Geoelectrical Classification of Gypsum Rocks     

Ander Guinea  Elisabet Playà  Lluís Rivero  Mahjoub Himi  Ricard Bosch 《Surveys in Geophysics》2010,31(6):557-580

Gypsum rocks are widely exploited in the world as industrial minerals. The purity of the gypsum rocks (percentage in gypsum mineral in the whole rock) is a critical factor to evaluate the potential exploitability of a gypsum deposit. It is considered than purities higher than 80% in gypsum are required to be economically profitable. Gypsum deposits have been studied with geoelectrical methods; a direct relationship between the electrical resistivity values of the gypsum rocks and its lithological composition has been established, with the presence of lutites being the main controlling factor in the geoelectrical response of the deposit. This phenomenon has been quantified in the present study, by means of a combination of theoretical calculations, laboratory measurements and field data acquisition. Direct modelling has been performed; the data have been inverted to obtain the mean electrical resistivity of the models. The laboratory measurements have been obtained from artificial gypsum-clay mixture pills, and the electrical resistivity has been measured using a simple electrical circuit with direct current power supply. Finally, electrical resistivity tomography data have been acquired in different evaporite Tertiary basins located in North East Spain; the selected gypsum deposits have different gypsum compositions. The geoelectrical response of gypsum rocks has been determined by comparing the resistivity values obtained from theoretical models, laboratory tests and field examples. A geoelectrical classification of gypsum rocks defining three types of gypsum rocks has been elaborated: (a) Pure Gypsum Rocks (>75% of gypsum content), (b) Transitional Gypsum Rocks (75–55%), and (c) Lutites and Gypsum-rich Lutites (<55%). From the economic point of view, the Pure Gypsum Rocks, displaying a resistivity value of >800 ohm.m, can be exploited as industrial rocks. The methodology used could be applied in other geoelectrical rock studies, given that this relationship between the resistive particles embedded within a conductive matrix depends on the connectivity of the matrix particles.  相似文献   

Hydrological response of a small mediterranean agricultural catchment     

Joan Estrany  Celso Garcia  Ramon J. Batalla 《Journal of Hydrology》2010,380(1-2):180-190

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Empirical fragility and vulnerability curves for buildings exposed to slow-moving landslides at medium and large scales   总被引：1，自引：0，他引：1  

Dario Peduto  Settimio Ferlisi  Gianfranco Nicodemo  Diego Reale  Giovanni Pisciotta  Giovanni Gullà 《Landslides》2017,14(6):1993-2007

Slow-moving landslides yearly induce huge economic losses worldwide in terms of damage to facilities and interruption of human activities. Within the landslide risk management framework, the consequence analysis is a key step entailing procedures mainly based on identifying and quantifying the exposed elements, defining an intensity criterion and assessing the expected losses. This paper presents a two-scale (medium and large) procedure for vulnerability assessment of buildings located in areas affected by slow-moving landslides. Their intensity derives from Differential Interferometric Synthetic Aperture Radar (DInSAR) satellite data analysis, which in the last decade proved to be capable of providing cost-effective long-term displacement archives. The analyses carried out on two study areas of southern Italy (one per each of the addressed scales) lead to the generation, as an absolute novelty, of both empirical fragility and vulnerability curves for buildings in slow-moving landslide-affected areas. These curves, once further validated, can be valuably used as tools for consequence forecasting purposes and, more in general, for planning the most suitable slow-moving landslide risk mitigation strategies.  相似文献   

Paleoenvironmental evolution of the Early Pleistocene lacustrine sequence at Barranco León archeological site (Orce,Baza Basin,Southern Spain) from stable isotopes and Sr and Mg chemistry of ostracod shells     

P. Anadón  M. Gabàs 《Journal of Paleolimnology》2009,42(2):261-279

Stable isotope and trace element contents of Cyprideis torosa valves from the Lower Pleistocene marginal lacustrine sequence of Barranco León, Baza Basin (Southern Spain), allow us to reconstruct the geochemical record of environmental change in this marginal area of the basin and to compare these data with the environmental changes inferred from the faunal associations. Hydrochemical features of the Baza Lake system have been influenced by changes in water source, solute composition, and water level during the past. Three water types may have been involved in a complex mixing in the marginal area during the studied intervals (1) waters of the Baza lacustrine system that underwent large P/E changes, (2) dilute, meteoric water inputs (surface and shallow groundwaters), (3) saline groundwater inputs of meteoric origin that acquired their salinity by halite and gypsum dissolution. Four stages in the Pleistocene paleoenvironmental evolution of the Barranco León area have been differentiated: stage I records a high lake level (highstand) of the saline closed-lake system. Stage II corresponds to very shallow, palustrine conditions. Stage III records the varying influence of the three water types under changing water level in a closed-lake. Stage IV corresponds to a through-flowing, open lacustrine environment mainly fed by meteoric saline groundwaters with minor inputs of stream waters. This small through-flowing lake was connected to a larger, inner saline closed-lake system. The BL 5 mammal site with lithic tools of an early human occupation phase in Western Europe corresponds to a particular episode within this stage of the environmental evolution in the marginal zone of the Baza Lake. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   

Indication for circular organization of column sprite elements associated with Eastern Mediterranean winter thunderstorms     

Elyakom Vadislavsky  Yoav Yair  Carynelisa Erlick  Colin Price  Eran Greenberg  Roy Yaniv  Baruch Ziv  Nàama Reicher  Adam Devir 《Journal of Atmospheric and Solar》2009,71(17-18):1835-1839

We report synchronized optical observations of sprites in Israel during the winters of 2006/7–2007/8. Based on several events, we suggest that the elements of columniform sprites are organized in spaced intervals on the circumference of a circle centered directly above, or a little offset, to the vertical direction from the parent lightning. In 2D images most of the cases show columns to be arranged in highly eccentric elliptical forms or in straight rows. The analysis of the optical images provided the geometrical dimensions of the columns and their spatial organization. We used an electrostatic model of the QE field with reasonable assumptions on the location and magnitude of the cloud charge center, constrained by ELF evaluation of the Charge Moment Change in the parent flash, to show that the observed diameter of the columnar arrangement closely matches the conventional breakdown field line contour at the same altitude.  相似文献   

History of vegetation during the Holocene in the Courel and Queixa Sierras,Galicia, northwest Iberian Peninsula     

Luisa Santos  Juan Ramon Vidal Romani  Guy Jalut 《第四纪科学杂志》2000,15(6):621-632

Palynological studies undertaken in the mountainous regions of the northwest of the Iberian Peninsula are few in number and have been concerned largely with the second half of the Holocene. New pollen data from two Galician sierras, the Courel and Queixa Sierras, provide a 10000‐yr record of vegetation and climate change. In the Courel Sierra before 9750 yr BP, Laguna Lucenza (1420 m a.s.l.) reflects a period of open landscape covered by Poaceae and heliophilous plants, which may be correlated with the Younger Dryas. The onset of the Holocene is characterised by the expansion of oak woodland, prior to 9300 yr BP, following a short phase of birch along with the gradual decline of pine. The oak values reach a peak at 8350 ± 80 yr BP. Towards 8800 yr BP Corylus begins to expand, followed by Alnus (7500 yr BP) and Ulmus. During this period, the Fraga pollen assemblage (Queixa Sierra, 1360 m a.s.l.) indicates Betula woodland surrounding the site, masking the regional predominance of oak. After 5000 yr BP there is a gradual decrease in arboreal pollen values in both Sierras. Castanea appears in Laguna Lucenza (Courel Sierra) at 4075 ± 75 yr BP. There is widespread deforestation during the last 4000 yr. During this period the presence of large quantities of microcharcoal particles points to the occurrence of fire. The reduction in forest is associated with the arrival of cultivation at 4000 yr BP at low altitudes in the Queixa Sierra. At higher altitudes the first agricultural activity is dated at later than 2000 yr BP. This coincides with the first record of cereal cultivation at high altitude in the Courel Sierra. Copyright © 2000 John Wiley & Sons, Ltd.  相似文献