Science.gov

Sample records for alface minimamente processada

  1. Pseudo-nitzschia spp. (Bacillariophyceae) and dissolved organic matter (DOM) dynamics in the Ebro Delta (Alfacs Bay, NW Mediterranean Sea)

    NASA Astrophysics Data System (ADS)

    Loureiro, Sofia; Garcés, Esther; Fernández-Tejedor, Margarita; Vaqué, Dolors; Camp, Jordi

    2009-08-01

    Samples were collected during one annual cycle (April 2007-March 2008) at Alfacs Bay (NW Mediterranean Sea) central station in order to assess the influence of organic nutrients in the growth of the microalgae assemblage, with special reference to Pseudo-nitzschia spp. This potentially toxic diatom forms natural and recurrent blooms in the study area. To assess further the relationship between Pseudo-nitzschia spp. and nutrients an enrichment experiment with high molecular weight dissolved organic matter (HMWDOM) was performed with field samples obtained during a Pseudo-nitzschia spp. bloom. HMWDOM was extracted from water collected at Alfacs Bay. Five bioassays were prepared: N + P (seawater with addition of nitrate and phosphate), DOM (addition of HMWDOM), (-N + P) + DOM (nitrogen deficient, with addition of phosphate and HMWDOM), (N + P) + DOM (addition of nitrate, phosphate and HMWDOM), seawater control (without added nutrients), and B + DOM (control of bacteria, without microalgae). The experiment was run in batch mode over 4 days. Results from the field study revealed that the concentrations of organic nutrients mostly surpassed the inorganic pool. Pseudo-nitzschia spp. was the most frequent and abundant taxa of the microalgae community. The micro-planktonic assemblage was arranged according to a seasonal factor (ANOSIM and cluster analysis). DON, nitrate and silicate were the most important abiotic parameters contributing to the dissimilarities between seasons (SIMPER analysis) and thereby potentially influencing the seasonal distribution of microalgae in the representative station. In the experimental investigation, Pseudo-nitzschia cells increased by the end of the experiment in the DOM bioassay but no respective increase was observed for chlorophyll a. This could point to an acquisition of nutrients through the DOM fraction that would conjointly reduce the need of chlorophyll a. The data obtained suggest that organic nutrients may exert an important role

  2. Protective actions of green tea polyphenols and alfacalcidol on bone microstructure in female rats with chronic inflammation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This study investigated the effects of green tea polyphenols (GTP) and alfacalcidol on bone microstructure and strength along with possible mechanisms in rats with chronic inflammation. A 12-week study using a 2 (no GTP vs. 0.5%, w/v GTP in drinking water) × 2 (no alfacalcidol vs. 0.05 ug/kg alfacal...

  3. Thermal oxidation of polycrystalline and single crystalline aluminum nitride wafers (Prop 2003-054)

    SciTech Connect

    Speakman, Scott A; Gu, Z; Edgar, J H; Blom, Douglas Allen; Perrin, J; Chaudhuri, J

    2006-10-01

    Two types of aluminum nitride (AlN) samples were oxidized in flowing oxygen between 900 C and 1150 C for up to 6 h - highly (0001) textured polycrystalline AlN wafers and low defect density AlN single crystals. The N-face consistently oxidized at a faster rate than the Al-face. At 900 C and 1000 C after 6 h, the oxide was 15% thicker on the N-face than on the Al-face of polycrystalline AlN. At 1100 C and 1150 C, the oxide was only 5% thicker on the N-face, as the rate-limiting step changed from kinetically-controlled to diffusion-controlled with the oxide thickness. A linear parabolic model was established for the thermal oxidation of polycrystalline AlN on both the Al- and N-face. Transmission electron microscopy (TEM) confirmed the formation of a thicker crystalline oxide film on the N-face than on the Al-face, and established the crystallographic relationship between the oxide film and substrate. The oxidation of high-quality AlN single crystals resulted in a more uniform colored oxide layer compared to polycrystalline AlN. The aluminum oxide layer was crystalline with a rough AlN/oxide interface. The orientation relationship between AlN and Al{sub 2}O{sub 3} was (0001) AlN//(10{bar 1}0) Al{sub 2}O{sub 3} and (1{bar 1}00) AlN//(01{bar 1}2) Al{sub 2}O{sub 3}.

  4. Hydrodynamic response in a microtidal and shallow bay under wind and seiche events

    NASA Astrophysics Data System (ADS)

    Cerralbo, Pablo; Grifoll, Manel; Espino, Manuel

    2016-04-01

    In this contribution we investigate the hydrodynamic response in Alfacs Bay (semi-enclosed bay in The Ebro Delta, NW Mediterranean Sea). The bay is micro-tidal, with a mixed tidal regime and a persistent hydrographic structure during most of the year (salty layer in the bottom and freshwater layer on top due to freshwater input from rice fields). Short-term response to energetic wind events was identified in the T/S and water velocity observations, sometimes inverting the estuarine circulation or developing one-layered flow. In comparison to previous investigations in Alfacs Bay, we observed that water current variability, and also maximum velocities, were directly related to the development of surface standing waves (i.e. seiches). Mixing mechanisms versus buoyancy sources are studied through adimensional numbers, potential energy anomaly equation and numerical model (ROMS), proving the leading freshwater contribution to stratification, enhanced by heat fluxes in summer. On the other hand, mixing is directly related to winds, mainly in winter and early spring when both buoyancy forces are lower. Seiche induced mixing is suggested as an eventual mechanism that may break the stratification within the Bay under special circumstances. Finally, the role of freshwater contribution to the estuarine circulation is analyzed as a possible mechanism influencing the water residence time in the bay and the different ecological problems associated.

  5. Modeling circulation patterns induced by spatial cross-shore wind variability in a small-size coastal embayment

    NASA Astrophysics Data System (ADS)

    Cerralbo, Pablo; Espino, Manuel; Grifoll, Manel

    2016-08-01

    This contribution shows the importance of the cross-shore spatial wind variability in the water circulation in a small-sized micro-tidal bay. The hydrodynamic wind response at Alfacs Bay (Ebro River delta, NW Mediterranean Sea) is investigated with a numerical model (ROMS) supported by in situ observations. The wind variability observed in meteorological measurements is characterized with meteorological model (WRF) outputs. From the hydrodynamic simulations of the bay, the water circulation response is affected by the cross-shore wind variability, leading to water current structures not observed in the homogeneous-wind case. If the wind heterogeneity response is considered, the water exchange in the longitudinal direction increases significantly, reducing the water exchange time by around 20%. Wind resolutions half the size of the bay (in our case around 9 km) inhibit cross-shore wind variability, which significantly affects the resultant circulation pattern. The characteristic response is also investigated using idealized test cases. These results show how the wind curl contributes to the hydrodynamic response in shallow areas and promotes the exchange between the bay and the open sea. Negative wind curl is related to the formation of an anti-cyclonic gyre at the bay's mouth. Our results highlight the importance of considering appropriate wind resolution even in small-scale domains (such as bays or harbors) to characterize the hydrodynamics, with relevant implications in the water exchange time and the consequent water quality and ecological parameters.

  6. Liquid chromatography coupled with tandem mass spectrometry to characterise trace levels of cyanobacteria and dinoflagellate toxins in suspended solids and sediments.

    PubMed

    Rivetti, Claudia; Gómez-Canela, Cristian; Lacorte, Silvia; Barata, Carlos

    2015-02-01

    Microcystins, anatoxins and okadaic acid are toxins produced by freshwater cyanobacteria and marine dinoflagellates. These toxins have been the responsible for the illness and death of biota and humans. To determine their presence in water during blooms, sensitive analytical methods are needed. In this study, we have developed a new liquid chromatography tandem mass spectrometry (LC-MS/MS) method for fast multiresidue determination of five toxins in suspended material and sediment samples. For each target compound, two selected reaction monitoring (SRM) transitions were optimised. Chromatographic conditions were optimised considering that the compounds analysed had different chemical structure and chromatographic behaviour. Using a Luna C18 column and specific SRM transitions, five phytotoxins were resolved. Method detection limits (MDL) for anatoxin-a, microcystins RR, LR and YR and okadaic acid were 7.1, 3.3, 81.7, 102.8 and 28.8 ng g(-1) dry weight in sediment, respectively. The developed analytical method was successfully applied to analyse the presence of toxins in suspended solids and sediment from Ebro River (NE Spain) and Ebro delta-associated lagoons. Anatoxin-a was detected downstream of the Riba-Roja reservoir with levels ranging from 20 to 1120 ng g(-1) dry weight of suspended solids. Okadaic acid was only detected in three samples collected in the Alfacs Bay (Ebro delta, Spain) affected by Dinophysis blooms in 2012.

  7. Seasonal uncoupling of demographic processes in a marine clonal plant

    NASA Astrophysics Data System (ADS)

    Mascaró, O.; Romero, J.; Pérez, M.

    2014-04-01

    In temperate regions, climatic factors impose a general seasonal pattern on seagrass growth that can be observed in leaf growth rates and, in small species, also in shoot density. Large variations in shoot density suggest a strong temporal uncoupling between shoot recruitment and shoot mortality, and the dependence of each of these processes on different drivers. Here we examine seasonal patterns of recruitment and mortality in the seagrass Cymodocea nodosa, one of the species most sensitive to seasonal forcing in the Mediterranean. We sampled two local populations submitted to different nutrient availability in Alfacs Bay (NW Mediterranean) and determined recruitment and mortality rates, as well as other plant traits, on a monthly basis. Our results confirm the hypothesized uncoupling, with maximum mortality 2 months after maximum recruitment. Whereas timing of recruitment was associated with light availability, and was supported by carbohydrate remobilisation, mortality was related to high water temperatures and probably also to light limitation in late summer due to self-shading. In the high-nutrient population, algal overgrowth caused further light deprivation, with mortality rates higher than in the low-nutrient population. It is emphasised that the demographic balance of the studied populations was negative for most of the year, with the exception of August and September. Therefore, caution is necessary when overall population trends are inferred from single annual sampling events.

  8. Cosmopolitan distribution of the large composite microbial mat spirochete, Spirosymplokos deltaeiberi

    NASA Technical Reports Server (NTRS)

    Margulis, L.; Navarrete, A.; Sole, M.

    1998-01-01

    Inocula from organic-rich black muds immediately underlying intertidal laminated microbial mats dominated by Microcoleus chthonoplastes yielded large, variable diameter spirochetes. These unusual spirochetes, previously reported only from the Alfacs Peninsula at the delta of the Ebro river in northeast Spain, contain striking arrays of cytoplasmic granules packed into their protoplasmic cylinders. On several occasions, both in summer and winter, the huge spirochetes were recognized in samples from mats growing in the Sippewissett salt marsh at Woods Hole Massachusetts. They were also seen in similar samples from microbial mats at North Pond, Laguna Figueroa, Baja California Norte, Mexico. The identity of these spirochetes was confirmed by electron microscopy: number and disposition of flagella, composite structure, measurements of their distinctive cytoplasmic granules. The granules, larger, more conspicuous and present in addition to ribosomes, are hypothesized to contain ATPases. As culture conditions worsen, these spirochetes retract into membrane-bounded round bodies in which they form refractile inclusions. From morphology and behavior we conclude the North American spirochetes from both Atlantic and Pacific intertidal microbial mats are indistinguishable from those at the delta of the Ebro river. We conclude a cosmopolitan distribution for Spirosymplokos deltaeiberi.

  9. Heavy metal content in oysters (Crassostrea gigas) cultured in the Ebro Delta in Catalonia, Spain.

    PubMed

    Ochoa, Victoria; Barata, Carlos; Riva, M Carmen

    2013-08-01

    The aim of this study was to determine heavy metal content (As, Cd, Cu, Hg, Cd, Pb, and Zn) in oysters transplanted in Ebro Delta bays (Alfacs and Fangar) where oysters are traditionally cultured for human consumption. Metal body burdens were monitored weekly during the period of maximal agriculture activity from May to June in 2008 and 2009. Results indicate that regardless of the high levels of metals reported in biota living in Ebro River, metal levels in oysters from both bays were similar to those found in unpolluted areas and far below the maximum limits of tolerance recommended by the European Commission. Nevertheless, metal accumulation patterns in oysters differentiate two sources of pollution: one coming from agriculture activities within the Ebro's delta for As, Cd, Cu, and Zn and other coming from Ebro River probably related to industrial activities upstream (Hg, Pb) or to lead shot pellets form hunting activities (Pb). Reported results, thus, are in concern with previous studies and indicate that metallic pollutants do not affect oysters cultures in Ebro Delta associated bays. PMID:23325313

  10. Understanding the spatio-temporal variability of phytoplankton biomass distribution in a microtidal Mediterranean estuary

    NASA Astrophysics Data System (ADS)

    Artigas, M. L.; Llebot, C.; Ross, O. N.; Neszi, N. Z.; Rodellas, V.; Garcia-Orellana, J.; Masqué, P.; Piera, J.; Estrada, M.; Berdalet, E.

    2014-03-01

    Understanding the spatio-temporal variability of phytoplankton in aquaculture zones is necessary for the prevention and/or prediction of harmful algal bloom events. Synoptic cruises, time series analyses of physical and biological parameters, and 3D modeling were combined to investigate the variability of phytoplankton biomass in Alfacs Bay at basin scale. This microtidal estuary located in the NW Mediterranean is an important area of shellfish and finfish exploitation, which is regularly affected by toxic outbreaks. Observations showed the existence of a preferential phytoplankton accumulation area on the NE interior of the bay. This pattern can be observed throughout the year, and we show that it is directly linked to the physical forcing in the bay, in particular, the interplay between freshwater input and wind-induced turbulence. Both drivers affect the strength of the estuarine circulation, explaining nearly 75% of the variability in phytoplankton biomass. More cells are retained when stratification is weakened and the estuarine circulation reduced, while flushing rates are higher during times of increased stratification and stronger estuarine flow. This has been confirmed by using a 3D hydrodynamic model with Eulerian tracers. Nutrients, while important to support phytoplankton populations, have been found to play only a secondary role in explaining this variability at basin scale.

  11. Citizens and satellites: Assessment of phytoplankton dynamics in a NW Mediterranean aquaculture zone

    NASA Astrophysics Data System (ADS)

    Busch, Julia A.; Price, Ivan; Jeansou, Eric; Zielinski, Oliver; van der Woerd, Hendrik J.

    2016-05-01

    Ocean colour measurements from space are well suited to assess phytoplankton dynamics over broad spatial scales. Closer to the coast however, the quality of these data degrades as a result of the loading of sediments and dissolved matter from terrestrial runoff, the influences of land reflection on atmospheric correction and sea-bottom reflection, which compromise their use in coastal management actions. Recently, the enabling of citizens to provide environmental observations has gained recognition as a way for enhancing the spatio-temporal coverage of satellite observations. In the FP7 funded EU project "Citclops" (Citizens' observatory for coast and ocean optical monitoring), a smart phone app for the classification of water colour, simplified to 21 hues of the Forel Ule (FU) scale, is developed. In this study we examine two bays in the Ebro Delta (NW Mediterranean) where satellite data, hyperspectral measurements, and observations with the citizen tool for colour comparison were available. FU values and their corresponding novel colorimetric parameter, the hue colour angle, were derived in the bay at 12 stations with the traditional FU scale and one automated in-situ radiometric system at the Alfacs Bay aquaculture site. Both methods complied well during the study course of May-June 2011. These measurements were further compared to data from Full Resolution MERIS (Medium Resolution Imaging Spectrometer) satellite images. The quality of the retrieved hue angle varies over the image. For high-quality sites, MERIS hue colour angles and FU values gave a good estimate of seasonal algal dynamics in the bays over the year 2011, while ground measurements revealed colour changes over short space- and time frames, which are indicative of the fast dynamics of phytoplankton in the area that could not be fully resolved with MERIS data. The use of FU values and hue colour angle of water will allow a simple integration of data from hyperspectral measurements, MERIS