Is proximity to land-based sources of coral stressors an appropriate measure of risk to coral reefs? An example from the Florida Reef Tract     

Lirman D  Fong P 《Marine pollution bulletin》2007,54(6):779-791

Localized declines in coral condition are commonly linked to land-based sources of stressors that influence gradients of water quality, and the distance to sources of stressors is commonly used as a proxy for predicting the vulnerability and future status of reef resources. In this study, we evaluated explicitly whether proximity to shore and connections to coastal bays, two measures of potential land-based sources of disturbance, influence coral community and population structure, and the abundance, distribution, and condition of corals within patch reefs of the Florida Reef Tract. In the Florida Keys, long-term monitoring has documented significant differences in water quality along a cross-shelf gradient. Inshore habitats exhibit higher levels of nutrients (DIN and TP), TOC, turbidity, and light attenuation, and these levels decrease with increasing distance from shore and connections to tidal bays. In clear contrast to these patterns of water quality, corals on inshore patch reefs exhibited significantly higher coral cover, higher growth rates, and lower partial mortality rates than those documented in similar offshore habitats. Coral recruitment rates did not differ between inshore and offshore habitats. Corals on patch reefs closest to shore had well-spread population structures numerically dominated by intermediate to large colonies, while offshore populations showed narrower size-distributions that become increasingly positively skewed. Differences in size-structure of coral populations were attributed to faster growth and lower rates of partial mortality at inshore habitats. While the underlying causes for the favorable condition of inshore coral communities are not yet known, we hypothesize that the ability of corals to shift their trophic mode under adverse environmental conditions may be partly responsible for the observed patterns, as shown in other reef systems. This study, based on data collected from a uniform reef habitat type and coral species with diverse life-history and stress-response patterns from a heavily exploited reef system, showed that proximity to potential sources of stressors may not always prove an adequate proxy for assigning potential risks to reef health, and that hypothesized patterns of coral cover, population size-structure, growth, and mortality are not always directly related to water quality gradients.  相似文献   

Dichotomy in host environments and signs of recycled active galactic nuclei     

Georgina V. Coldwell  Diego G. Lambas  Ilona K. Söchting  Sebastián Gurovich 《Monthly notices of the Royal Astronomical Society》2009,399(1):88-96

We analyse the relation between active galactic nuclei (AGN) host properties and large-scale environment for a representative red and blue AGN host galaxy sample selected from the Data Release 4 Sloan Digital Sky Survey. A comparison is made with two carefully constructed control samples of non-active galaxies, covering the same redshift range and colour baseline. The cross-correlation functions show that the density distribution of neighbours is almost identical for blue galaxies, either active or non-active. Although active red galaxies inhabit environments less dense compared to non-active red galaxies, both reside in environments considerably denser than those of blue hosts. Moreover, the radial density profile of AGN relative to galaxy group centres is less concentrated than galaxies. This is particularly evident when comparing red AGN and non-active galaxies.
The properties of the neighbouring galaxies of blue and red AGN and non active galaxies reflect this effect. While the neighbourhood of the blue samples is indistinguishable, the red AGN environs show an excess of blue-star-forming galaxies with respect to their non-active counterpart. On the other hand, the active and non-active blue systems have similar environments but markedly different morphological distributions, showing an excess of blue early-type AGN, which are argued to be late-stage mergers. This comparison reveals that the observable differences between active red and blue host galaxy properties including star formation history and AGN activity depends on the environment within which the galaxies form and evolve.  相似文献   

Forecasting monthly precipitation in Central Chile: a self-organizing map approach using filtered sea surface temperature   总被引：1，自引：0，他引：1  

Diego Rivera  Mario Lillo  Cintia B. Uvo  Max Billib  José Luis Arumí 《Theoretical and Applied Climatology》2012,107(1-2):1-13

Western South America is subject to considerable inter-annual variability due to El Ni?o–Southern Oscillation (ENSO) so forecasting inter-annual variations associated with ENSO would provide an opportunity to tailor management decisions more appropriately to the season. On one hand, the self-organizing maps (SOM) method is a suitable technique to explore the association between sea surface temperature and precipitation fields. On the other hand, Wavelet transform is a filtering technique, which allows the identification of relevant frequencies in signals, and also allows localization on time. Taking advantage of both methods, we present a method to forecast monthly precipitation using the SOM trained with filtered SST anomalies. The use of the SOM to forecast precipitation for Chillan showed good agreement between forecasted and measured values, with correlation coefficients (r ²) ranging from 0.72 to 0.91, making the combined use filtered SST fields and SOM a suitable tool to assist water management, for example in agricultural water management. The method can be easily tailored to be applied in other stations or to other variables.  相似文献   

Elastic behavior of vanadinite,Pb<Subscript>10</Subscript>(VO<Subscript>4</Subscript>)<Subscript>6</Subscript>Cl<Subscript>2</Subscript>, a microporous non-zeolitic mineral     

G. Diego Gatta  Yongjae Lee  Chi-Chang Kao 《Physics and Chemistry of Minerals》2009,36(6):311-317

The high-pressure behavior of a vanadinite (Pb₁₀(VO₄)₆Cl₂, a = b = 10.3254(5), c = 7.3450(4) Å, space group P6₃/m), a natural microporous mineral, has been investigated using in-situ HP-synchrotron X-ray powder diffraction up to 7.67 GPa with a diamond anvil cell under hydrostatic conditions. No phase transition has been observed within the pressure range investigated. Axial and volume isothermal Equations of State (EoS) of vanadinite were determined. Fitting the P–V data with a third-order Birch-Murnaghan (BM) EoS, using the data weighted by the uncertainties in P and V, we obtained: V ₀ = 681(1) Å³, K ₀ = 41(5) GPa, and K′ = 12.5(2.5). The evolution of the lattice constants with P shows a strong anisotropic compression pattern. The axial bulk moduli were calculated with a third-order “linearized” BM-EoS. The EoS parameters are: a ₀ = 10.3302(2) Å, K ₀(a) = 35(2) GPa and K′(a) = 10(1) for the a-axis; c ₀ = 7.3520(3) Å, K ₀(c) = 98(4) GPa, and K′(c) = 9(2) for the c-axis (K ₀(a):K ₀(c) = 1:2.80). Axial and volume Eulerian-finite strain (fe) at different normalized stress (Fe) were calculated. The weighted linear regression through the data points yields the following intercept values: Fe _a (0) = 35(2) GPa for the a-axis, Fe _c (0) = 98(4) GPa for the c-axis and Fe _V (0) = 45(2) GPa for the unit-cell volume. The slope of the regression lines gives rise to K′ values of 10(1) for the a-axis, 9(2) for the c-axis and 11(1) for the unit cell-volume. A comparison between the HP-elastic response of vanadinite and the iso-structural apatite is carried out. The possible reasons of the elastic anisotropy are discussed.  相似文献   

Geochemical hazard evaluation of sulphide-rich iron mines: The Rio Marina district (Elba Island,Italy)     

Diego Servida  Giovanni GriecoLuisa De Capitani 《Journal of Geochemical Exploration》2009

Rio Marina mining district (Elba Island) is characterised by hematite + pyrite ore association and was exploited for iron till 1981, leaving waste rock dumps of several millions m³. The effect of open pit mining activity in this site is to produce acid mine drainage (AMD) processes leading to environmental pollution, testified by all the sampled waters (Giove stream, drainage channels, superficial pools and settling basin) which have pH values ranging from 2.08 to 3.35 and heavy metal concentrations that reach 903.16 mg/l for Fe, 45.02 mg/l for Mn, 10.08 mg/l for Zn and 1.75 mg/l for Cu. In the present work a space and time related approach to geochemical hazard evaluation was applied. The geochemical hazard is mainly related to high heavy metal concentration, acid mine drainage processes development and topographic setting. As all these parameters are related in space, hazard evaluation was performed by geostatistical methods. Fifty-four earth material samples (residual soils, waste rocks or debris materials) were collected in a central aligned 100 m mesh square grid. These were analysed for major elements by XRF, for Cu, Pb, Zn by ICP-AES and for AMD potential following the AMIRA procedure. The concentration of heavy metals was compared with Italian law limits. The overlap of Cu, Pb and Zn content maps show that at least one of these heavy metals exceed law limits in all the area. The AMD test results show that more than 50% of samples have a positive NAPP (Net Acid Producing Potential) that could reach 258.9 kg H₂SO₄/t. According to the obtained data, three main geochemical hazard classes were established and their distribution in the mining area was assessed. About 51% of the mining area surface belongs to the major hazard class, where AMD process occurs, about 49% belongs to an intermediate hazard class, where AMD process could occur only if certain conditions are met. Finally, the persistence of the AMD process in the Rio Marina area was evaluated on the basis of yearly rainfall, mining waters pH and NAPP values. A complete leaching of the first 0.25 m of the earth materials can retain the current environmental conditions for several centuries.  相似文献   

The first crocodyliform from the Chubut Group (Chubut Province, Argentina) and its phylogenetic position within basal Mesoeucrocodylia     

Juan Martín Leardi  Diego Pol   《Cretaceous Research》2009,30(6):1376-1386

A new crocodyliform specimen is presented here found in the Cerro Castaño Member of the Cerro Barcino Formation (Chubut Group). The material consists of cranial and postcranial remains that represent a new taxon that has strong affinities with Peirosauridae, but also shares derived features present in Araripesuchus. The phylogenetic relationships of this new taxon were tested through a cladistic analysis depicting it as a member of the Peirosauridae. The inclusion of Barcinosuchus within this clade of basal mesoeucrocodylians is supported by the presence of hypapophyses up to the third or fourth dorsal vertebrae, anterolateral facing edge on postorbital, quadrate dorsal surface divided in two planes by a ridge; mandibular symphysis tapering anterirorly in ventral view, lateral surface of dentary convex anterior to mandibular fenestra, distal body of quadrate well developed, anteroposteriorly thin and lateromedially broad. The new specimen broadens the temporal and geographical distribution of Peirosauridae during the Cretaceous of Gondwana, representing the southern-most and the most ancient record of the group in Patagonia. The new material also provides insights on the postcranial anatomy of peirosaurids, a group that has been so far studied almost exclusively from cranial material.  相似文献   

Exceptional preservation processes of 3D dinosaur footprint casts in Costalomo (Lower Cretaceous,Cameros Basin,Spain)     

Pedro Huerta  Fidel Torcida Fernández‐Baldor  James O. Farlow  Diego Montero 《地学学报》2012,24(2):136-141

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New evidence for the presence of reindeer (Rangifer tarandus) on the Iberian Peninsula in the Pleistocene: an archaeopalaeontological and chronological reassessment     

Asier Gómez‐Olivencia  Diego Arceredillo  Diego J. Álvarez‐Lao  Diego Garate  Ziortza San Pedro  Pedro Castaños  Joseba Rios‐Garaizar 《Boreas: An International Journal of Quaternary Research》2014,43(2):286-308

Reindeer (Rangifer tarandus) populations reached the Iberian Peninsula during the end of the Middle Pleistocene and there are numerous examples of this species from Late Pleistocene Mousterian and Upper Palaeolithic sites. In this paper, new evidence of reindeer in the east Cantabrian region is presented that further supports the timing of this species’ first appearance, and previous assessments are updated. To date, the presence of this species has been identified at 55 sites in the Iberian Peninsula, nearly as many as those of mammoth (Mammuthus primigenius) and woolly rhinoceros (Coelodonta antiquitatis) combined. Most of the sites with presence of reindeer (50) are located in the Cantabrian region with a clear increase in the density of sites and remains towards the Pyrenees. The remaining five sites with evidence of reindeer are located on the other side of the Pyrenees in the NW corner of Catalonia. In contrast, archaeological evidence of reindeer in the form of art (both parietal and portable) is more scarce and scattered. Evidence for the representation of these animals has been found outside the northern fringe of the Iberian Peninsula, which could reflect either long‐distance cultural communication or the movement of human groups.  相似文献   

Southern dispersal and Palaeoecological implications of woolly rhinoceros (Coelodonta antiquitatis): review of the Iberian occurrences     

Diego J. Álvarez-Lao  Nuria García 《Quaternary Science Reviews》2011,30(15-16):2002-2017

Cold-adapted large mammal populations spread southward during the coldest and driest phases of the Late Pleistocene reaching the Iberian Peninsula. Presence of woolly rhinoceros (Coelodonta antiquitatis) can be identified from 23 Iberian sites, which is compiled and analyzed herein, and the fossil specimens from seven of these sites are described here for first time.Morphological and biometrical analyses demonstrate that the Iberian woolly rhinoceros did not significantly differ from individuals of other European populations, but represent the westernmost part of a continuous Eurasian belt of distribution.The first presence of woolly rhino in the Iberian Peninsula has been identified during the late Middle Pleistocene and early Late Pleistocene. However, the highest abundance of this species is recorded during MIS 3 and 2. The latest Iberian occurrences can be dated around 20 ka BP. The presence of woolly rhinoceros in the Iberian Peninsula correlates with periods of extreme dry and cold climatic conditions documented in Iberian terrestrial and marine sediment sequences.From a palaeobiogeographic point of view, the maximum southern spread of C. antiquitatis on the Iberian Peninsula was registered during the late Middle Pleistocene or early Late Pleistocene, reaching the latitude of Madrid (about 40°N). Subsequently, during MIS 3 and 2, all Iberian finds were restricted to the Northern regions of Iberia (Cantabrian area and Catalonia). The southern expansion of C. antiquitatis during the Late Pleistocene in the Iberian Peninsula reached similar latitudes to other Eurasian regions.The ecological composition of fossil assemblages with presence of woolly rhinoceros was statistically analyzed. Results show that temperate ungulate species are predominant at Iberian assemblages, resulting in a particular mixture of temperate and cold elements different of the typical Eurasian cold-adapted faunal associations. This particular situation suggests two possible explanations: a) Eventual migrations during the coldest time spans, resulting in a mixing of cold and temperate faunas, instead a faunal replacing; b) Persistence of woolly rhinoceros populations in the Iberian Peninsula during interglacial episodes confined at cryptic southern refugia.  相似文献   

Imaging the Moho and Subducted Oceanic Crust at the Isthmus of Tehuantepec, Mexico, from Receiver Functions     

Diego Melgar  Xyoli P��rez-Campos 《Pure and Applied Geophysics》2011,168(8-9):1449-1460

Using teleseismic data recorded along a transect, which we call VEOX (for Veracruz-Oaxaca seismic line), of 46 broadband stations installed across the Isthmus of Tehuantepec in southern Mexico, we obtained receiver functions and stacked them to study the Moho topography and back projected them to visualize the subducted slab geometry beneath the isthmus. We observed a back-azimuth dependent Moho thickness across the transect, particularly beneath the Los Tuxtlas Volcanic Field. Also, we observed the Cocos plate which subducts with an angle of 26° between 140 and 310?km from the trench. Comparison with regional seismicity indicates that it occurs below the oceanic crust.  相似文献