Erosion‐initiated stromatolite and thrombolite formation in a present‐day coastal sabkha setting     

Andreas Paul  Stephen W. Lokier  Angela Sherry  Luiza Lessa Andrade  Wesley M. Court  Cees van der Land  Kirsten E. Dutton  Ian M. Head 《Sedimentology》2021,68(1):382-401

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Groundwater response to climate variability in Mediterranean type climate zones with comparisons of California (USA) and Portugal     

Malmgren  Katherine A.  C. Neves  Maria  Gurdak  Jason J.  Costa  Luis  Monteiro  Jos&#; P. 《Hydrogeology Journal》2022,30(3):767-782

Hydrogeology Journal - Aquifers are a fundamental source of freshwater, yet they are particularly vulnerable in coastal regions with Mediterranean type climate, due to both climatic and...  相似文献   

Geochronology,sediment provenance,and fossil emplacement at Sumidouro Cave,a classic late Pleistocene/early Holocene Paleoanthropological site in eastern Brazil     

Luís B. Pil  Augusto S. Auler  Walter A. Neves  Xianfeng Wang  Hai Cheng  R. Lawrence Edwards 《Geoarchaeology》2005,20(8):751-764

Peter Wilhelm Lund's (1845a) heavily debated suggestion of a contemporaneity between Paleo‐Indians and extinct Pleistocene fauna at Sumidouro Cave was re‐examined through detailed sedimentological and geochronological analyses of sediment and both human and faunal remains. Sources of the cave's sediment include both entrances as well as ceiling fissures. Non‐human fossils, on the other hand, were probably carried by floodwater through the once more‐spacious swallet entrance. Seasonal flooding reworked and mixed these two highly asynchronous assemblages. U‐series and radiocarbon ages indicate that there are at least two distinct episodes of sediment input in the cave, at ˜240,000 yr B.P. and ˜8000 yr B.P. Human remains represent a later emplacement event, probably at ˜8400 cal yr B.P. Although the human remains are of considerable age, the cave's complex stratigraphy, flooding dynamics, and extensive removal of the cave's filling during earlier excavations do not allow the determination of an unequivocal co‐existence between Paleo‐Indians and extinct megafauna at the site. © 2005 Wiley Periodicals, Inc.  相似文献   

Experimental and computational synergy for modelling an advanced gas-cooled reactor core under seismic excitation     

Luiza Dihoru  Olafur Oddbjornsson  Ben Cannell  Adam J. Crewe  Tony Horseman  Matt Dietz  Colin A. Taylor 《地震工程与结构动力学》2020,49(13):1308-1328

The advanced gas-cooled reactors (AGRs) are the backbone of the United Kingdom's nuclear generation fleet, producing approximately 17% of the country's electricity. Their safety cases are supported by thorough inspection and monitoring of their graphite cores and extensive theoretical, analytical, and experimental studies. This paper presents a unique, highly innovative and technically challenging earthquake engineering project that has provided vital evidence to underpin the seismic safety assessments of the AGRs. Two modelling approaches, one experimental (a multilayer array physical model), and one numerical (a SOLFEC nonsmooth contact dynamics computational model) have been developed to investigate the seismic behaviour of an aged graphite core. The synergetic relationship between the two approaches is a product of insightful collaborative learning between the University of Bristol and Atkins, with the experiments providing material parameters and validation data and the computer simulations feeding array design and test schedule recommendations to the physical model. The predictive capabilities of the physical and the numerical models are tested by direct comparison and the good agreement between the results has increased the confidence in both. The model's versatility allows a variety of core scenarios to be tested that can explore in detail the AGR core behaviour in seismic conditions.  相似文献   

Understanding how environmental heterogeneity and elevation drives the distribution of woody communities across vegetation types within the campo rupestre in South America     

Marcelo Leandro BUENO  Vanessa Leite REZENDE  Luiza Fonseca A.DE PAULA  Joo Augusto Alves MEIRA-NETO  José Roberto Rodrigues PINTO  Andreza Viana NERI  Vanessa PONTARA 《山地科学学报》2021,(5):1192-1207

The campo rupestre sensu lato is a vegetation type that occurs in South American mountains, supports a distinctive flora characterized by high rates of endemism, high herbaceous species richness and often-neglected but also species-rich of the arboreal stratum. We aimed to investigate how environmental factors and elevation are associated with the distribution and diversity of woody species in different rupestrian vegetation types across South America. Using a database of 2,049 woody species from 185 sites across four vegetation types within the campo rupestre, we assessed how the vegetation types were grouped according to their floristic composition and number of shared indicator species, as well as by using different beta diversity indices. The most important variables from a set of 27 variables(e.g. altitude, geo-edaphic and climatic) explaining species distribution were identified using redundancy analysis(RDA) and variation partitioning methods. The distribution of vegetation types was related to both environmental and spatial fractions, with a set of 17 variables retained(e.g. rockiness, grass cover and temperature seasonality as the most important variables). There was an association between the floristic composition of each vegetation type and the elevation range. Although the identified vegetation types are floristically related, they are distinguished by exclusive and habitat-specialist woody species. This uniqueness of vegetation types should be considered in terms of complementarity for the conservation of campos rupestres.  相似文献   

The autonomous <Emphasis Type="Italic">Simpatico</Emphasis> system for real-time continuous water-quality and current velocity monitoring: examples of application in three Portuguese estuaries     

Erwan Garel  Susana Nunes  João Magalhães Neto  Rodrigo Fernandes  Ramiro Neves  João Carlos Marques  Óscar Ferreira 《Geo-Marine Letters》2009,29(5):331-341

This technical paper describes an autonomous recording system with remote data access for the continuous, long-term in situ monitoring of water quality and discharge, as well as current velocity. The Simpatico system has been recently deployed in three estuaries in Portugal (Mondego and Tagus in July 2007; Guadiana in March 2008), highly suitable to illustrate its multifaceted potential applications: surveillance of the effects of mitigation measures to combat eutrophication (lower Mondego Estuary); real-time implementation of boundary conditions for a water modelling system (upper Tagus Estuary); study of dam-induced impacts in terms of water quality, water discharge and sediment budgets (mouth of the Guadiana Estuary). An extract of recorded data serves as an example to discuss data reliability, as well as field maintenance of the system, with implications for labour and operational costs. The use of a new generation of copper-based anti-biofouling kits significantly reduced the need for field maintenance operations. Other examples of possible application of the system include the assessment of gas accumulation in coastal waters.  相似文献   

Effects of a nuclear power plant thermal discharge on habitat complexity and fish community structure in Ilha Grande Bay, Brazil   总被引：1，自引：0，他引：1  

Tatiana Pires Teixeira  Leonardo Mitrano Neves  Francisco Gerson Araújo   《Marine environmental research》2009,68(4):188-195

Fish communities and habitat structures were evaluated by underwater visual censuses a rocky location impacted by thermal discharge (I) and at two control locations, one in a Sargassum bed (C1) and the other in a rocky shore with higher structural complexity (C2). Habitat indicators and fish communities exhibited significant differences between the impacted and control locations, with the impacted one showing a significant decrease in fish species richness and diversity, as well as a decrease in benthic cover. At the I location, only 13 fish species were described, and the average water temperature was 32 ± 0.4 °C, compared with 44 species at C1 (25.9 ± 0.3 °C) and 33 species at C2 (24.6 ± 0.2 °C). Significant differences in fish communities among locations were found by ANOSIM with Eucinostomus argenteus, Mugil sp. and Haemulon steindachneri typical of location I, while Abudefduf saxatilis, Stegastes fuscus and Malacoctenus delalandi were typical of the control locations. Our study shows that thermal pollution alters benthic cover and influences fish assemblages by altering composition and decreasing richness.  相似文献   

Paleolimnologically inferred eutrophication of a shallow, tropical, urban reservoir in southeast Brazil     

Sandra Costa-B?ddeker  Helen Bennion  Tatiane Araújo de Jesus  Ana Luiza S. Albuquerque  Rubens C. L. Figueira  Denise de C. Bicudo 《Journal of Paleolimnology》2012,48(4):751-766

We studied the eutrophication history of a tropical shallow reservoir in the S?o Paulo metropolitan region, southeast Brazil. We analyzed grain size, geochemistry, diatom assemblages, and land-use records in a sediment core from the reservoir to infer its trophic state history during the last ~110?years (1894?C2005). Eighty diatom species were observed in the core and shifts in the relative abundances of planktonic and benthic taxa indicate major limnological changes associated with complex interactions between hydrologic factors and eutrophication. Discostella stelligera was associated with deforestation and water physical changes whereas Aulacoseira granulata, a species abundant throughout the core, was mostly associated with high flux conditions and erosion events, regardless of trophic state. Eutrophication was triggered by construction of the city zoo (1958) and installation of the S?o Paulo State Department of Agriculture (1975) within the Gar?as watershed, and increasing loads of untreated sewage from these institutions. The data suggest that deterioration in water quality began after ~1975 and markedly accelerated after ~1990. The reservoir has been hypereutrophic since 1999. Steady increases in geochemical proxies for trophic state, along with a decrease in C/N ratios, indicated higher nutrient concentrations and the prevalence of autochthonous production towards the core top. Appearance of Achnanthidium catenatum ~1993 highlighted the onset of a marked eutrophication phase. The subsequent dominance of Planothidium rostratum and Cyclotella meneghiniana suggested a sharp shift to a hypereutrophic state since 1999. Land-use history proved valuable for validating the chronology and interpreting anthropogenic impacts. Multi-proxy analysis of the sediment record provided an effective tool for tracking ecological shifts in the reservoir ecosystem. This study provides the first reconstruction of lake eutrophication history in Brazil and highlights the importance of hydrological/physical changes as drivers of diatom assemblage shifts in reservoirs, which may confound trophic state inferences based on shifts in the planktonic/benthic diatom ratio.  相似文献   

Spatial variability and temporal stability of throughfall in a eucalyptus plantation in the hilly lowlands of southeastern Brazil   总被引：2，自引：0，他引：2  

Anderson Mululo Sato  André de Souza Avelar  Ana Luiza Coelho Netto 《水文研究》2011,25(12):1910-1923

Throughfall has been widely studied in forests but there is a scarcity of studies that focus on the spatial variability and temporal stability of throughfall in eucalyptus plantations. We examined throughfall in a daily basis in a 2·5‐year eucalyptus plantation in southeastern Brazil using three sample arrangements: (1) close to tree trunks (CT) and in the central point between trunks (BT), (2) four‐radial layout centred in tree trunk and (3) eight‐radial layout. Throughfall was spatially non‐uniform and varied according to the spatial monitoring arrangement: accumulated throughfall/precipitation ratio of 146% (CT) and 85% (BT) in arrangement 1, mean throughfall of 88% in arrangement 2, 84% (hilltop) and 85% (side slope) in arrangement 3. The highest throughfall values, spatial variability and persistence of dry and wet conditions were found close to eucalyptus trunks. Often accumulated throughfall close to trunks exceeded rainfall, especially for long‐duration rainfall > 5 mm. The ‘funnel effect’ was consistently observed in all three arrangements and we speculate that the high throughfall concentration and temporal stability are related to canopy structures of eucalyptus. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Structure and dynamics of distinct fish assemblages in three reaches (upper,middle and lower) of an open tropical estuary in Brazil     

Leonardo M. Neves  Tatiana P. Teixeira  Francisco G. Araújo 《Marine Ecology》2011,32(1):115-131

We collected fishes and environmental variables in three zones (upper, middle and lower) of a small open tropical estuary during flood tide. The aim was to test for differences in fish assemblages along a gradient from freshwater to marine waters and to detect any seasonal variation in fishes and environmental variables across these zones. A total of 111 species (18 in the upper, 50 in the middle and 66 in the lower estuary) were recorded, forming three distinct fish assemblages, with the family Eleotridae dominating in the upper, Gerreidae in the middle, and Sciaenidae in the lower estuary. Only two species (Geophagus brasiliensis in the upper and the middle zones, and Eucinostomus argenteus in the middle and the lower zones) composed more than 1% of the total number of individuals in more than a single zone. Short‐term (tidal) changes in salinity in the middle estuary were associated with different assemblages in the three estuarine zones, even in winter, when the differences in salinity are lowest between the middle and the lower zones. Seasonal variation in salinity was irrelevant, except in a protected sidewater lagoon in the middle estuary. Low salinity seasonal change may be related to the lack of seasonal variation in the structure of fish assemblages in all estuarine zones.  相似文献