In situ experimental decomposition studies in estuaries: A comparison of Phragmites australis and Fucus vesiculosus     

Marta Lobo Lopes  Patrícia Martins  Fernando Ricardo  Ana Maria Rodrigues  Victor Quintino 《Estuarine, Coastal and Shelf Science》2011,92(4):497-580

The decomposition rates of Phragmites australis and Fucus vesiculosus were experimentally determined in an estuarine system using the leaf-bag technique. The study was conducted in fifteen sites arranged in five areas, extending from freshwater, outside the tidal range, to the marine environment, near the mouth of the estuary. The leaf-bags (5 mm mesh), were set up with 3.0 g of dried substrate, submerged in the experimental sites at day 0 and collected at days 3, 7, 15, 30 and 60, to follow biomass loss. The biomass loss through the leaching phase (day 3) was about 16% for Phragmites australis and 33% for Fucus vesiculosus and was independent of salinity for both substrates. The difference in the remaining biomass between the two species increased with time and the decomposition rates differed along the salinity gradient. For F. vesiculosus, the decomposition rate was highest near the mouth of the estuary, corresponding to the preferential distribution area of the algae, and decreased towards freshwater. For Phragmites australis, the fastest decay was observed in the mid estuary, where Phragmites australis occurs naturally, confirming previous studies. The decomposition rates measured at different time intervals (0–15, 0–30 and 0–60 days) were always higher for the algae and decreased with time for both species. These results indicate that the use of decomposition rates as a measure of ecosystem integrity or quality status in transitional waters will not be straightforward and must take into account, among others, the test species, the study area positioning along the estuarine gradient, and the time interval for the calculation of the decomposition rate.  相似文献   

Benthic habitat mapping: Concerns using a combined approach (acoustic, sediment and biological data)     

Rosa Freitas  Fernando Ricardo  Fbio Pereira  Leandro Sampaio  Susana Carvalho  Miguel Gaspar  Victor Quintino  Ana Maria Rodrigues 《Estuarine, Coastal and Shelf Science》2011,92(4):72

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Relationship between metal levels in the vent mussel Bathymodiolus azoricus and local microhabitat chemical characteristics of Eiffel Tower (Lucky Strike)     

Inês Martins  Richard P. CossonVirginie Riou  Pierre-Marie SarradinJozée Sarrazin  Ricardo S. SantosAna Colaço 《Deep Sea Research Part I: Oceanographic Research Papers》2011,58(3):306-315

The turbulent mixing of hydrothermal hot fluid with cold seawater creates large chemical gradients at a small spatial scale that may induce variable physiological and biochemical adaptations within the vent fauna. The adaptation to such a variable environment by the vent mussel Bathymodiolus azoricus relies on a dual symbiosis hosted in the gills, and digestion of particulate organic matter. The surrounding environment not only provides the necessary energy sources and suspended organic particles for the vent mussel nutrition, but also potentially toxic compounds such as metals. Our main goal was to see if there is a relation between metal accumulation in mussel organs and the chemical characteristics of their close environment. Mussels were collected at six locations in a cold part of the Eiffel Tower fluid-seawater mixing zone, characterized by distinct chemical compositions. Metals (Cd, Cu, Fe and Zn) and metallothioneins were quantified in the gills and digestive gland. The physiological condition of the sampled mussels was also evaluated using tissues and gill indices. Our study indicates that the accumulation of metals in B. azoricus is related to their spatial distribution and linked to fine scale environmental conditions that influence the physiological status of the organism.  相似文献   

Surface atmospheric circulation patterns and associated minimum temperatures in the Maipo and Casablanca valleys, central Chile     

Carlo Montes  Ricardo C. Muñoz  Jorge F. Perez-Quezada 《Theoretical and Applied Climatology》2013,111(1-2):275-284

This paper analyzes the influence of circulation anomalies on the magnitude of minimum air temperature (T _min) at a daily scale in two important agricultural valleys of Chile (Maipo and Casablanca) during the period 2001–2007. A statistical classification of synoptic fields was performed, resulting in eight circulation patterns (CPs, 84 % of explained variance). The corresponding anomalies of T _min (AT_min) of each CP were analyzed in order to understand their synoptic-scale forcing mechanisms. Results showed a direct association between AT_min and the synoptic structure. The average weakening in sea level pressure (SLP) yields positive AT_min, while negative AT_min is associated with a strengthening in SLP. In the latter case, it was also found that a synoptic structure (10.2 % of frequency) corresponding to a migratory high-pressure system passing eastward across the Andes led to the lowest AT_min and a higher probability of frost in both valleys (22 % on average) in winter and springtime.  相似文献   

Laser Ablation in the Synthesis of Zirconium Oxide     

Ricardo Castell  Thierry Poirier 《Astrophysics and Space Science》1997,256(1-2):539-545

Results of an experimental study of the oxidation of a zirconium plasma generated by laser ablation of a metallic target under low pressures of oxygen are presented. The crystallographic identification of the collected product by electronic diffraction shows metastable ZrO cubic phase. The oxidation phenomena are interpreted by thermochemical simulation suggesting a model in accordance with other cases of synthesis of metastable oxides at high temperatures, such as plasma reactors.  相似文献   

A model of characteristic earthquakes and its implications for regional seismicity     

Ricardo López-Ruiz  Miguel Vázquez-Prada  Javier B. Gómez  Amalio F. Pacheco 《地学学报》2004,16(3):116-120

Regional seismicity (i.e. that averaged over large enough areas over long enough periods of time) has a size–frequency relationship, the Gutenberg–Richter law, which differs from that found for some seismic faults, the Characteristic Earthquake relationship. But all seismicity comes in the end from active faults, so the question arises of how one seismicity pattern could emerge from the other. The recently introduced Minimalist Model of Vázquez‐Prada et al. of characteristic earthquakes provides a simple representation of the seismicity originating from a single fault. Here, we show that a Characteristic Earthquake relationship together with a fractal distribution of fault lengths can accurately describe the total seismicity produced in a region. The resulting earthquake catalogue accounts for the addition of both all the characteristic and all the non‐characteristic events triggered in the faults. The global accumulated size–frequency relationship strongly depends on the fault length fractal exponent and, for fractal exponents close to 2, correctly describes a Gutenberg–Richter distribution with a b exponent compatible with real seismicity.  相似文献   

Streamflow dynamics in a Mediterranean temporary river     

Joan Estrany  Celso Garcia  Ricardo Alberich 《水文科学杂志》2013,58(5):717-736

Abstract

Mediterranean rivers are characterized by the irregularity of flow, harsh hydrological fluctuations and a profound transformation as the result of human activity. In this study, we investigate the streamflow response of a Mediterranean temporary river in which different groundwater, agriculture and urban contributions play an important role. Streamflow was measured at three nested gauging stations installed along Na Borges River, a lowland agricultural catchment (319 km²) on the island of Mallorca. Based on two hydrological years (2004/05 and 2005/06), potential evapotranspiration and surface water–groundwater interaction generated a succession of four different hydrological periods playing an important role in baseflow dynamics. The runoff coefficients were very low (<5%). At the event scale, groundwater also controlled runoff response, being very different according to hydrogeology, antecedent conditions and human impacts. During dry seasons, wastewater and karstic spring discharges maintain an influent regime into some streams. As a result, intense rainstorms in late summer generated water volumes over the impervious urban surfaces involved, with the result that quickflow was significant because the hydrological pathways were active. Citation Estrany, J., Garcia, C. & Alberich, R. (2010 Estrany, J., Garcia, C. and Batalla, R. J. 2010. Hydrological response of a small Mediterranean agricultural catchment. J. Hydrol., 380(1-2): 180–190. doi:10.1016/j.jhydrol.2009.10.035[Crossref] , [Google Scholar]) Streamflow dynamics in a Mediterranean temporary river. Hydrol. Sci. J. 55(5), 717–736.   相似文献   

Pilocarpus microphyllus seedling growth threatened by climate change: an ecophysiological approach     

Amaral  Genilda Canuto  Pezzopane  José Eduardo Macedo  de Souza Nóia Júnior  Rogério  Martínez  Manuel Fernández  Fonseca  Mariana Duarte Silva  Gibson  Elbya Leão  Toledo  João Vitor  Pezzopane  José Ricardo Macedo  Klippel  Valéria Hollunder  Xavier  Talita Miranda Teixeira 《Theoretical and Applied Climatology》2022,147(1-2):347-361

Theoretical and Applied Climatology - The climate change endangers many species of the Amazon Forest. An example, in the endangered medicinal species Pilocarpus microphyllus (popularly known as...  相似文献   

Constraining Sources of Organic Matter to Tropical Coastal Sediments: Consideration of Nontraditional End-members     

R. A. Briggs  K. C. Ruttenberg  B. T. Glazer  A. E. Ricardo 《Aquatic Geochemistry》2013,19(5-6):543-563

Molar organic carbon to total nitrogen to organic phosphorus (OC:TN:OP) ratios are used in tandem with carbon isotopic values to constrain sources of organic matter (OM) to marine sediments in a tropical coastal embayment. Analysis of end-members specific to the study site indicates that the bulk OM pool cannot be modeled as a simple mixture of two end-members (terrestrial vs. marine OM), but rather reflects a more complex, multicomponent mixture. Mangrove, coral reef ecosystems, and bacterial biomass contribute OM to tropical coastal marine sediments that is compositionally distinct from traditional marine and terrestrial end-members and thus preclude the application of a classical two end-member mixing model of the sort that has been used traditionally in sediments from temperate environments. A survey of elemental ratios and carbon isotopic values of potential OM end-members reported in the literature, as well as depth profiles before and after whole-core incubation experiments conducted as part of this study, were used to evaluate the strength of OC:TN versus OC:OP ratios as OM source indices. Our study suggests that OC:TN ratios are a weaker indicator of OM source than OC:OP ratios, because: (1) the more restricted dynamic range of OC:TN ratios prevents clear distinction of terrestrial-from marine-derived OM, and (2) post-depositional changes in OC:TN ratios occur during diagenesis, obscuring the source signature of initially deposited OM. The fidelity of OM indices during early diagenesis underscores the importance of quantifying OP in sediments to assess sedimentary OM source.  相似文献   

A Note on Solar Cycle Length During the Medieval Climate Anomaly     

José M. Vaquero  Ricardo M. Trigo 《Solar physics》2012,279(1):289-294

The growing interest in the Medieval Climate Anomaly (MCA) and its possible link to anomalous solar activity has prompted new reconstructions of solar activity based on cosmogenic radionuclides. However, these proxies do not sufficiently constrain the total solar irradiance (TSI) range and are often defined at low temporal resolution, inadequate to infer the solar-cycle length (SCL). We have reconstructed the SCL (average duration of 10.72±0.20 years) during the MCA using observations of naked-eye sunspot and aurora sightings. The solar activity was probably not exceptionally intense, supporting the view that internal variability of the coupled ocean–atmosphere system was the main driver of the MCA.  相似文献