The Chan Hol cave near Tulum (Quintana Roo,Mexico): evidence for long‐lasting human presence during the early to middle Holocene          下载免费PDF全文

Fabio Hering  Wolfgang Stinnesbeck  Jens Folmeister  Eberhard Frey  Sarah Stinnesbeck  Jerónimo Avilés  Eugenio Aceves Núñez  Arturo González  Alejandro Terrazas Mata  Martha Elena Benavente  Carmen Rojas  Adriana Velázquez Morlet  Norbert Frank  Patrick Zell  Julia Becker 《第四纪科学杂志》2018,33(4):444-454

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Spatio-temporal variability of benthic macroalgae in a coral reef system highly influenced by fluvial discharge: Veracruz,Gulf of Mexico     

Guillermo Horta-Puga  José Luis Tello-Musi  Alejandro Córdova  Adriana Gutiérrez-Carrillo  Jhoan Gutiérrez-Martínez  Aura Aletse Morales-Aranda 《Marine Ecology》2020,41(4):e12596

The Veracruz Reef System, in the southern Gulf of Mexico, is a suitable area for the study of the temporal and spatial variability of macroalgae abundance, at reef settings influenced by the fluvial discharge of the Jamapa River, and by human activities in the city and port of Veracruz. With this purpose, the bottom cover of each morpho-functional group of benthic macroalgae (frondoses, turf, and crustose corallines), and hermatypic corals, was determined at ten selected coral reefs, on a seasonal basis (rainy and dry seasons), for the 2009–2015 period. The average cover of benthic macroalgae was high (53.1%), with turf as the dominant morpho-functional group (31.9%), as in several reef ecosystems in the tropical Atlantic, followed by crustose corallines (15.2%), and frondoses (6.1%). Although turf macroalgae is dominant, due to their high temporal and spatial variability, the Veracruz Reef System could not be considered to be in a stable state, but just in an intermediate unstable equilibrium state, which is highly influenced by a high sediment load. As expected, nearshore reefs presented higher macroalgae covers, and unexpectedly, the outer-shelf reefs presented the highest cover of frondoses. Despite fluvial discharge influence, no differences in cover were found between the rainy and dry seasons. There was a negative and significantly correlation between the cover of frondoses and turf, which suggests that the driver/s of the abundance of these macroalgae, act in opposite ways for each group. Three clusters of reefs, defined by community structure and conservation degree, were determined: nearshore or degraded, offshore or moderately conserved, and conserved; and the entire Veracruz Reef System is considered to be in a moderately state of conservation.  相似文献   

Development of mirrors made of chemically tempered glass foils for future X-ray telescopes     

Bianca Salmaso  Marta Civitani  Claudia Brizzolari  Stefano Basso  Mauro Ghigo  Giovanni Pareschi  Daniele Spiga  Laura Proserpio  Yves Suppiger 《Experimental Astronomy》2015,39(3):527-545

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Filter-feeder macroinvertebrates as key players in culturable bacteria biodiversity control: a case of study with Sabella spallanzanii (Polychaeta: Sabellidae)     

Licciano M  Terlizzi A  Giangrande A  Cavallo RA  Stabili L 《Marine environmental research》2007,64(4):504-513

The present study investigates the effect of the filtering activity of Sabella spallanzanii on the culturable heterotrophic bacterial community through the comparison of the bacterial diversity in transplanted polychaetes and the surrounding seawater. For isolation of culturable heterotrophic bacteria, seawater samples as well as polychaete homogenates were plated in triplicates onto Bacto Marine Agar 2216 (Difco). All the colonies grown were isolated, subcultured and identified by several morphological, biochemical and cultural methods. Some bacterial genera showed higher average abundances in polychaetes than in seawater (i.e. Lucibacterium and Photobacterium). Aeromonas represented a conspicuous component of the bacterial community both in S. spallanzanii and seawater. The presence of Cytophaga and Pseudomonas was also relevant in the examined seawater samples. The selective concentrations of some bacterial genera inside S. spallanzanii either by grazing on bacteria or their capability as bacterial reservoirs, provides evidence for the role of macrobenthic invertebrates as key determinants for microbial diversity.  相似文献   

Depuration dynamics of oysters (Crassostrea gigas) artificially contaminated by Salmonella enterica serovar Typhimurium     

de Abreu Corrêa A  Albarnaz JD  Moresco V  Poli CR  Teixeira AL  Oliveira Simões CM  Monte Barardi CR 《Marine environmental research》2007,63(5):479-489

The State of Santa Catarina produces the greatest quantity of edible mollusks in Brazil. To guarantee sanitary qualify, mollusk cultures should be monitored for contamination by pathogenic microorganisms. A self-purification or "depuration" system that eliminates Salmonella enterica serovar Typhimurium contamination from oysters has been developed and evaluated. The depuration process occurred within a closed system, in which 1000 L of water was recirculated for 24 h. The water was sterilized with ultraviolet (UV) light, chlorine, or both together. Oysters (Crassostrea gigas) artificially contaminated with S. typhimurium were harvested every 6 h. Samples of oyster tissue were excised and both the presence and numbers of bacteria were determined. Combined UV light and chlorine treatments resulted in total elimination of bacteria within 12 h. Polymerase chain reaction detected bacteria in water exposed to the three treatments. This pioneering study is the first of its kind in Brazil and represents a major contribution to commercial mollusk culture in this country.  相似文献   

Annelids in Modern Biology     

Adriana Giangrande  Maria Cristina Gambi 《Marine Ecology》2010,31(3):522-523

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Trace element concentrations in the Mexico‐Belize ejecta layer: A link between the Chicxulub impact and the global Cretaceous‐Paleogene boundary     

Jane Wigforss‐Lange  Vivi Vajda  Adriana Ocampo 《Meteoritics & planetary science》2007,42(11):1871-1882

Abstract— Four exposures of Chicxulub impact ejecta along the Mexico‐Belize border have been sampled and analyzed for major and trace element abundances. The ejecta deposits consist of a lower spheroid bed, containing clay and dolomite spheroids, and an upper diamictite bed with boulders and clasts of limestone and dolomite. The matrix of both beds is composed of clay and micritic dolomite. The rare earth element (REE) compositions in the matrix of both units show strong similarities in concentrations and pattern. Furthermore, the Zr/TiO₂ scatter plot shows a linear correlation indicating one source. These results indicate that the basal spheroid bed has the same source and was generated during the same event as the overlying diamictite bed, which lends support to a single‐impact scenario for the Albion Formation ejecta deposits. The elevated concentrations of non‐meteoritic elements such as Sb, As, U, and Zn in the matrix of the lower spheroid bed are regarded to have been derived from the sedimentary target rocks at the Chicxulub impact site. The positive Eu and Ce anomalies in clay concretion and in the matrix of the lower part of the spheroid bed in Albion Island quarry is probably related to processes involved in the impact, such as high temperature and oxidizing conditions. Analogous trace element anomalies have been reported from the distal Cretaceous‐Paleogene (K/T) boundary clay layer at different sites. Thus, the trace element signals, reported herein, are regarded to support a genetic link between the Chicxulub impact, the ejecta deposits along the Mexico‐Belize border, and the global K/T boundary layer.  相似文献   

An observational study of heat fluxes and their relationships with net radiation     

Dario Camuffo  Adriana Bernardi 《Boundary-Layer Meteorology》1982,23(3):359-368

Experimental evidence indicates that the diurnal behaviour of the fluxes of heat into the ground and into the atmosphere versus the net flux of radiation can be modelled by closed curves, the hourly values folowing one another in either a clockwise or counter clockfashion. A general formulation to express the different heat fluxes as a function of net radiation is proposed. This relationship between the different heat fluxes and can be expressed as a sum of three terms: the first indicates a direct proportionality to , the second gives the deviation from linearity and depends on /t, and the third gives the value of the flux when = 0. The formulae are then expressed as a function of time and the ratios between the heat fluxes and are evaluated. A comparison with the approximations generally used shows that the latter may be considered as particular cases of the more general equations proposed here.  相似文献   

Destructive effects of oxygen starvation and ash falls on benthic life: A pilot study     

Maria Bianca Cita  Massimo Podenzani 《Quaternary Research》1980,13(2):230-241

A quantitative study on faunal density and faunal diversity was carried out on benthic foraminifers from 15 samples of two eastern Mediterranean deep-sea cores. Samples were taken beneath, within, and above three distinctive levels well correlatable for over 1000 km: (a) Sapropel S-5, late Pleistocene in age, correlative with marine isotopic stage 5e and with the Tyrrhenian transgression, with an interpolated age of ～ 125,000 yr: (b) the “Ischia” tephra Y-5, the most widespread ash layer of the eastern Mediterranean, correlative with the transition from isotopic stages 3 to 2 and having an interpolated age of ～ 35,000 yr; and (c) Sapropel S-1, Holocene in age, correlative with the Flandrian transgression, radiometrically dated at ～8000 yr B.P. The most severe effects on benthic life were induced by stagnation (a). Deglaciation corresponding to Termination II was so rapid that the benthic assemblages could not adapt themselves to the too-rapidly decreasing oxygen levels and were entirely destroyed. More than 1000 yr after the termination of stagnant conditions no recolonization had yet started. The lesser disturbance was induced in the benthic community by the ash fall (b). The faunal destruction was ephemeral in duration and the colonizing population did not differ from that predating the ash fall. A progressive faunal change, with increasing abundance of taxa tolerant to low oxygen levels, was recorded beneath Sapropel S-1 (c). The recolonizing assemblage differs from the previously existing one, and is more similar to those recorded from the floor of the Mediterranean.  相似文献   

Sediment hosted lead–zinc deposits of the Neoproterozoic Bambuí Group and correlative sequences, São Francisco Craton, Brazil: A review and a possible metallogenic evolution model   总被引：3，自引：0，他引：3  

Aroldo Misi  Sundaram S.S. Iyer  Carlos Eduardo S. Coelho  Colombo C.G. Tassinari  Washington J.S. Franca-Rocha  Ion de Abreu Cunha  Adriana S. Rocha Gomes  Tolentino Flvio de Oliveira  Joo Batista G. Teixeira  Valter Mnaco C. Filho 《Ore Geology Reviews》2005,26(3-4):263-304

The Proterozoic sediment-hosted Zn–(Pb) sulfide and non-sulfide deposits of the São Francisco Craton, Brazil, are partially syn-diagenetic and epigenetic and were probably formed during extensional events. The majority of the deposits occur within shallow water dolomites. The Pb isotopic data of sulfides are relatively homogeneous for individual deposits and plot above the upper crust evolution curve of the Plumbotectonic model. Some of the deposits are characterized by highly radiogenic lead (²⁰⁶Pb/²⁰⁴Pb ≥ 21) originating from the highly radioactive crust of the São Francisco Craton. Pb and S isotopic data suggest the sources of metal and sulfur for the deposits to be the basement rocks and seawater sulfates in the sediments, respectively. The relatively high temperatures of formation (100 to 250 °C) and moderate salinity (3% to 20% NaCl equiv.) of the primary fluid inclusions in the sphalerite crystals suggest the participation of basinal mineralizing fluids in ore formation. The steep paleo-geothermal gradient generated by the radioactively enriched basement rocks probably assisted in heating up the circulating mineralizing fluids.  相似文献