Impacts of urban wastewater discharge on seagrass meadows (Zostera noltii)     

Susana Cabaço  Raquel MachásVasco Vieira  Rui Santos 《Estuarine, Coastal and Shelf Science》2008

The abiotic disturbance of urban wastewater discharge and its effects in the population structure, plant morphology, leaf nutrient content, epiphyte load and macroalgae abundance of Zostera noltii meadows were investigated in Ria Formosa coastal lagoon, southern Portugal using both univariate and multivariate analysis. Four sites were assessed, on a seasonal basis, along a gradient from a major Waste Water Treatment Works (WWTW) discharge to a main navigation channel. The wastewater discharge caused an evident environmental disturbance through the nutrient enrichment of the water and sediment, particularly of ammonium. Zostera noltii of the sites closest to the nutrient source showed higher leaf N content, clearly reflecting the nitrogen load. The anthropogenic nutrient enrichment resulted in higher biomass, and higher leaf and internode length, except for the meadow closest to the wastewater discharge (270 m). The high ammonium concentration (158–663 μM) in the water at this site resulted in the decrease of biomass, and both the leaf and internode length, suggesting a toxic effect on Z. noltii. The higher abundance of macroalgae and epiphytes found in the meadow closest to the nutrient source may also affect the species negatively. Shoot density was higher at the nutrient-undisturbed site. Two of the three abiotic processes revealed by Principal Component Analysis were clearly related to the WWTW discharge, a contrast between water column salinity and nutrient concentration and a sediment contrast between both porewater nutrients and temperature and redox potential. A multiple regression analysis showed that these abiotic processes had a significant effect on the biomass-density dynamics of meadows and on the overall size of Z. noltii plants, respectively. Results show that the wastewater discharge is an important source of environmental disturbance and nutrients availability in Ria Formosa lagoon affecting the population structure, morphology and N content of Z. noltii. This impact is spatially restricted to areas up to 600 m distant from the WWTW discharge, probably due to the high water renewal of the lagoon.  相似文献   

Total Mercury Distribution and Volatilization in Microcosms with and Without the Aquatic Macrophyte Eichhornia Crassipes     

Raquel Rose Silva Correia  Diana Ciannella Martins de Oliveira  Jean Remy Davée Guimar?es 《Aquatic Geochemistry》2012,18(5):421-432

Mercury (Hg) is one of the most toxic pollutants and spreads in the environment according to its affinity to several compartments. Aquatic macrophytes, such as Eichhornia crassipes, are known as sites for accumulation of Hg and methylmercury formation. The objective of this research was to observe Hg distribution among air, water and whole plants of the macrophyte E. crassipes for 17?days. The distribution of a single ²⁰³Hg spike was evaluated by gamma spectrometry. Two experiments, with and without macrophytes, were made, and the compartments analyzed for the presence of Hg were air, 0.2-μm filtered water, suspended and settled particles, roots, leafs, petioles and adsorption on the desiccators walls. ²⁰³Hg was detected in all analyzed compartments, and the highest total Hg concentrations were found in the roots and particles of the incubations with and without macrophytes that retained in average 68 and 34?% of added Hg, respectively. On the other hand, the lowest concentrations were found in air for both incubations, with higher volatilization (up to 2.5?% of added Hg) in the absence of macrophytes. The lower Hg values in leafs and petioles suggest this plant has mechanisms of Hg retention in the roots. Results suggest this macrophyte promotes changes in the Hg cycle since it attracts most Hg present in water and particulate to its roots and settled particles underneath and also reduces Hg volatilization.  相似文献   

Studies of pulsations on sdBs: structural models and frequency calculations     

Raquel Oreiro  Ana Ulla  Fernando Pérez Hernández  James MacDonald  Ramón García  María Rosa Zapatero 《Astrophysics and Space Science》2004,291(3-4):411-418

We have calculated the structural models of sdB stars and their corresponding theoretical frequencies needed to carry out an asteroseismological analysis.  相似文献   

Rainfall patterns in the Southern Amazon: a chronological perspective (1971–2010)     

Nathan S. Debortoli  Vincent Dubreuil  Beatriz Funatsu  Florian Delahaye  Carlos Henke de Oliveira  Saulo Rodrigues-Filho  Carlos Hiroo Saito  Raquel Fetter 《Climatic change》2015,132(2):251-264

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Coffee growth,pest and yield responses to free-air CO2 enrichment     

Raquel Ghini  André Torre-Neto  Anamaria F. M. Dentzien  Oliveiro Guerreiro-Filho  Regiane Iost  Flávia R. A. Patrício  Jeanne S. M. Prado  Roberto A. Thomaziello  Wagner Bettiol  Fábio M. DaMatta 《Climatic change》2015,132(2):307-320

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The influence of environmental variability of a coastal lagoon ecosystem on genetic diversity and structure of white seabream [Diplodus sargus (Linnaeus 1758)] populations          下载免费PDF全文

Raquel Hernández‐García  Irene Muñoz  Antonio López‐Capel  Concepción Marcos  Ángel Pérez‐Ruzafa 《Marine Ecology》2015,36(4):1144-1154

As coastal lagoons serve as nursery areas for some marine and estuarine fish, selective pressures of these brackish or hypersaline lagoons may influence the genetic structure of species and populations. We examined spatial and temporal genetic patterns at eight microsatellite loci in white seabream [Diplodus sargus (Linnaeus 1758)] recruits from the Mar Menor (Southeast Spain) and compared these loci with those in coastal populations from the open sea, observing a high degree of genetic diversity and spatio‐temporal genetic stability. However, the results suggest the presence of subpopulations or genetic substructures in the Mar Menor D. sargus population that could be interpreted as a homogeneous mixture of individuals from three differentiated subpopulations in the Mediterranean and evidence of the Wahlund effect. It also suggests that D. sargus adults return to their original spawning habitat, thus conserving the genetic differences among the respective populations over time. Overall, this study demonstrates the importance of the Mar Menor coastal lagoon as a nursery area for the conservation of genetic diversity of D. sargus populations.  相似文献   

Arabia Terra,Mars: Tectonic and Palaeoclimatic Evolution of a Remarkable Sector of Martian Lithosphere     

Anguita  Francisco  Anguita  Jorge  Castilla  Gabriel  De La Casa  Miguel-Angel  Domínguez  José-María  Herrera  Raquel  Llanes  Pilar  López  Mónica  Martínez  Vicente 《Earth, Moon, and Planets》1997,77(1):55-72

A regional geologic study of Arabia Terra, a densely cratered area of Mars northern hemisphere, has revealed the individuality of this province. This is best expressed by an equatorial belt with a crater age distinctly younger as compared to the northern part of Arabia Terra and to Noachis Terra to the south. We interpret this as an incipient back-arc system provoked by the subduction of Mars lowlands under Arabia Terra during Noachian times. The regional fracture patterns are also best explained in this manner, making it unnecessary to appeal to a rotational instability of the planet, which is not supported by the palaeoclimatic indicators in the area. This model could be the first regional-scale confirmation of Sleep's (1994) hypothesis of a limited plate consumption as an explanation of the martian dichotomy. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Igneous garnet and amphibole fractionation in the roots of island arcs: experimental constraints on andesitic liquids   总被引：12，自引：8，他引：4  

Raquel Alonso-Perez  Othmar Müntener  Peter Ulmer 《Contributions to Mineralogy and Petrology》2009,157(4):541-558

To evaluate the role of garnet and amphibole fractionation at conditions relevant for the crystallization of magmas in the roots of island arcs, a series of experiments were performed on a synthetic andesite at conditions ranging from 0.8 to 1.2 GPa, 800–1,000°C and variable H₂O contents. At water undersaturated conditions and fO₂ established around QFM, garnet has a wide stability field. At 1.2 GPa garnet + amphibole are the high-temperature liquidus phases followed by plagioclase at lower temperature. Clinopyroxene reaches its maximal stability at H₂O-contents ≤9 wt% at 950°C and is replaced by amphibole at lower temperature. The slopes of the plagioclase-in boundaries are moderately negative in space. At 0.8 GPa, garnet is stable at magmatic H₂O contents exceeding 8 wt% and is replaced by spinel at decreasing dissolved H₂O. The liquids formed by crystallization evolve through continuous silica increase from andesite to dacite and rhyolite for the 1.2 GPa series, but show substantial enrichment in FeO/MgO for the 0.8 GPa series related to the contrasting roles of garnet and amphibole in fractionating Fe–Mg in derivative liquids. Our experiments indicate that the stability of igneous garnet increases with increasing dissolved H₂O in silicate liquids and is thus likely to affect trace element compositions of H₂O-rich derivative arc volcanic rocks by fractionation. Garnet-controlled trace element ratios cannot be used as a proxy for ‘slab melting’, or dehydration melting in the deep arc. Garnet fractionation, either in the deep crust via formation of garnet gabbros, or in the upper mantle via formation of garnet pyroxenites remains an important alternative, despite the rare occurrence of magmatic garnet in volcanic rocks.  相似文献   

A new biostratigraphic correlation for Late Cretaceous–Paleocene strata of the Gulf of Guinea: Evidence from dinoflagellate cysts     

Raquel Sánchez-Pellicer  Edwige Masure  Loïc Villier 《Comptes Rendus Geoscience》2017,349(1):32-41

A new biostratigraphic correlation for Late Cretaceous and Palaeocene strata of the Côte d’Ivoire–Ghana continental margin has been developed from the identification of significant dinoflagellate cyst events in ODP Hole 959D. The Late Cretaceous stage boundaries are mostly consistent with previous studies. However, the Maastrichtian/Danian boundary is placed much lower than previously recognized on the basis of the first occurrences of Carpatella cornuta and Damassadinium californicum. The base of the Selandian is recognized from the last occurrence of Cerodinium diebelii and the first occurrence of Adnatosphaeridium multispinosum. The base of the Thanetian is recognized from the first occurrence of Areoligera gippingensis. The rarity of the age-marker taxa is the main reason for different age determinations among studies of the same section.  相似文献   

Monitoring of the groundwater chemical status in the Azores archipelago (Portugal) in the context of the EU water framework directive   总被引：1，自引：0，他引：1  

José Virgílio Cruz  Dina Pacheco  Raquel Cymbron  Sandra Mendes 《Environmental Earth Sciences》2010,61(1):173-186

A main challenge associated to EU Water Framework Directive corresponds to groundwater monitoring, both quantitative and chemical. The need for monitoring was also stressed by the Azores Water Plan. Monitoring of the chemical status of groundwater in Azores started in 2003 and has been progressively enlarged to all islands, totalizing 72 springs and 32 wells. A large number of parameters are analysed biannually, as major, minor and trace elements, pesticides and total hydrocarbons, as well as microbial indicators. Spring waters are mainly from HCO₃–Na type; instead water from wells is predominantly from the Cl–Na type, been differences attributed to their respective hydrogeologic framework. Springs discharge mainly from perched-water bodies, been influenced mainly from CO₂ in soils, silicate weathering, and seawater spraying and aerosols. Wells are in basal bodies, therefore subject to seawater intrusion influence, and 9% of Cl analyses made in wells exceed the standard value. Heavy metals, metalloids, hydrocarbons and pesticides all comply with standard values. Agriculture pollution also influences groundwater quality, as revealed by both NO₃ and PO₄ content, been the guide value exceeded respectively in 8 and 9% of the analyses. Despite the discontinuous variation of coliforms over time microbial indicators present an impact on water quality.  相似文献