A comparative analysis of time–depth relationships derived from scientific ocean drilling expeditions     

Sauermilch  Isabel  Mateo  Zenon Richard P.  Boaga  Jacopo 《Marine Geophysical Researches》2019,40(4):635-641

Marine Geophysical Research - Time–depth relationships (TDR) are required for correlating geological information from drill sites with seismic reflection profiles. Conventional...  相似文献   

Depth of closure: New calculation method based on sediment data     

Luis Aragonés  Jose Ignacio Pagán  Isabel López  José C.Serra 《国际泥沙研究》2018,33(2):198-207

Obtaining depth of closure (DoC) in an accurate manner is a fundamental issue for coastal engineering, since good results for coastal structures and beach nourishment depend mainly on DoC. Currently, there are two methods for obtaining the DoC, mathematical formulations and profile surveys. However, these methods can incur important errors if one does not take into account the characteristics and morphology of the area, or if one does not have a sufficiently long time series. In this work the DoC is obtained from the break in the trend of the sediment with the depth, that is, in general with the increase of the depth a decrease in the size of the sediment takes place. However, at one point this tendency changes and the size increases, and then decreases again. When comparing the point where the minimum sediment size occurs before the increase, it is observed that the error incurred is small compared to other methods. If the Standard Deviation of Depth Change (SDDC) method is considered as the most accurate method, the error incurred by the proposed method is less than 7%. In addition, it can be seen that the dispersion of the sediment method always occurs outside the zone of bar movement. Whereas in the methods of profiles survey (using 2 cm precision profiles), sometimes the DoC is obtained within the active zone of bar movement. In addition, where the relative minimum of the median sediment size is found, and the sizes of 0.063 and 0.125 mm predominate in the composition of the sample. Therefore, this new method allows the precise location of the DoC to be obtained in a fast and simple way. Furthermore, this method has the advantage that it is not affected by the modifications that may be experienced by both the study area and the cross-shore beach profile.  相似文献   

A Road to Conflict: Stakeholder’s and Social Network Analysis of the Media Portrayals of a Social-Environmental Conflict in Bolivia     

Victoria Reyes-García  Oriol Andrés-Conejero  Álvaro Fernández-Llamazares  Isabel Díaz-Reviriego  José-Luis Molina 《社会与自然资源》2019,32(4):452-472

Society’s understanding of a conflict is mediated by information provided in mass media, for which researchers stress the importance of analyzing media portrays of stakeholders in a conflict. We analyze information from the Bolivian press regarding the construction of a road crossing the Isiboro-Sécure Indigenous Territory and National Park (TIPNIS). Using stakeholder’s and social network analyses, we explore stakeholder’s positions and alliances as represented in the media and contrast it with previous scholarly work. We found that some actors cited as central in scholar analyses of the conflict are largely absent in the media (e.g., private investors, conservationist sector) and that the media tend to present stakeholders as having more homogeneous positions than the academic literature does while also neglecting some important alliances in their account. The media also suggests that Indigenous communities are forging stronger alliances with urban sectors and civil society, alliances not stressed by researchers.  相似文献   

Trends and correlations in annual extreme precipitation indices for mainland Portugal, 1941–2007     

M. Isabel P. de Lima  Fátima Espírito Santo  Alexandre M. Ramos  Ricardo M. Trigo 《Theoretical and Applied Climatology》2015,119(1-2):55-75

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Spatial gradients in plant leaf wax D/H across a coastal salt marsh in southern California     

Isabel C. Romero  Sarah J. Feakins 《Organic Geochemistry》2011,42(6):618-629

Coastal salt marsh ecosystems contain strong environmental gradients that are anticipated to influence the D/H ratios recorded in the leaf waxes of salt-tolerant plants. We characterized the molecular and hydrogen isotopic composition of alkanes in plant and sediment samples as well as the D/H ratios of environmental and plant waters across an elevation and inundation gradient in a southern Californian, coastal salt marsh. We sampled the dominant salt marsh plant species: Salicornia virginica, Arthrocnemum subterminale and Jamuea carnosa (all succulents), as well as Monanthochloe littoralis and Limonium californicum (nonsucculents). Plant xylem water hydrogen isotopic compositions indicate a shift in source waters from meteoric influences at upland sites (δD value −20‰) to seawater dominated values (0‰) at lowland areas. We found leaf water D enrichment relative to xylem water ranging from mean δD values of +54‰ (upland) to +28‰ (lowland), interpreted as a reduction of transpiration with increasing inundation time. This has the effect of increasing the net fractionation between source water and leaf wax product across the environmental gradient from mean values of −101‰ (upland) to −134‰ (lowland), with an attenuated signal recorded in the δD values of plant leaf wax n-alkanes (−122‰ to −136‰). These results constrain the hydrogen isotopic composition of salt marsh organic matter that may contribute to marine carbon budgets of the Santa Barbara Basin, and further indicate the potential for plant leaf waxes to resolve paleoenvironmental change, including sea level change, in sediment cores from salt marsh ecosystems.  相似文献   

Patterns of rare earth and other trace elements in different size fractions of clays of Campanian–Maastrichtian deposits from the Portuguese western margin (Aveiro and Taveiro Formations)     

Rosa Marques  M. Isabel Prudêncio  M. Isabel Dias  Fernando Rocha 《Chemie der Erde / Geochemistry》2011,71(4):337-347

The Upper Cretaceous (Campanian–Maastrichtian) Taveiro and Aveiro Formations belong to the northern sector of the Lusitanian basin (Portuguese western margin). The Taveiro Formation was deposited in alluvial fans, including mud flow beds, lakes and sinuous rivers. The Aveiro Formation was deposited in a flat region with low hydrodynamics channels, with the formation of a barrier island-tidal system. The reconstruction of this sedimentary basin may be difficult due to its complex architecture. This work aims a methodology to be used in the reconstruction of Cretaceous sedimentary environments of the Lusitanian basin, through the establishment of geochemical patterns of different size fractions of those deposits. Chemical analysis was performed by instrumental neutron activation analysis (INAA), and the mineralogical composition obtained by X-ray diffractometry (XRD). The whole rock and different size fractions (? ≥ 125 μm, 63–125 μm, 20–63 μm, 2–20 μm and ? < 2 μm) of selected samples were studied aiming the rare earth elements (REE) and other trace elements distribution and its correlation with the grain size and mineralogy.The results obtained for the studied Cretaceous sediments showed that REE patterns and other trace elements distribution in the different size fractions may be used as a tool to differentiate deposits within and between sedimentary formations. Within the Taveiro Formation, REE are concentrated in the silt fractions (20–63 μm and 2–20 μm) of the Reveles deposit, and in the clay size fraction of S. Pedro deposit, which is richer in kaolinite. The 1st transition elements, particularly Zn, are correlated with the presence of smectite in the clay fraction of Reveles deposit. In the sand and silt size fractions (>2 μm) of samples from Taveiro Formation correlations were found between: Ga and 1st transition elements, and phyllosilicates; Cs and mica; and Rb and Ba, and K–feldspars.The Bustos deposit (Aveiro Formation) samples are very fine-grained and with a high proportion of the fine silt fraction where REE are concentrated, especially the heavy ones. Incorporation of MREE, Co and U in carbonates of the coarser fraction appears to occur. The abundances of the 1st transition elements, Ga and As, are correlated with phyllosilicates.Significant differences were found in the trace elements patterns of the various analysed size fractions of the Lusitanian basin of Cretaceous sediments, between and even within formations, which can be used as a methodological approach for a fine paleogeographic reconstruction.  相似文献   

Effects of seawater acidification on early development of the intertidal sea urchin Paracentrotus lividus (Lamarck 1816)     

Laure Moulin  Ana Isabel Catarino  Thomas Claessens  Philippe Dubois 《Marine pollution bulletin》2011,62(1):48-54

The effect of pH ranging from 8.0 to 6.8 (total scale - pH_T) on fertilization, cleavage and larval development until pluteus stage was assessed in an intertidal temperate sea urchin. Gametes were obtained from adults collected in two contrasting tide pools, one showing a significant nocturnal pH decrease (lowest pH_T = 7.4) and another where pH was more stable (lowest pH_T = 7.8). The highest pH_T at which significant effects on fertilization and cleavage were recorded was 7.6. On the contrary, larval development was only affected below pH_T 7.4, a value equal or lower than that reported for several subtidal species. This suggests that sea urchins inhabiting stressful intertidal environments produce offspring that may better resist future ocean acidification. Moreover, at pH_T 7.4, the fertilization rate of gametes whose progenitors came from the tide pool with higher pH decrease was significantly higher, indicating a possible acclimatization or adaptation of gametes to pH stress.  相似文献   

Palaeoceanographic changes in the North Atlantic during the Mid‐Pleistocene Transition (MIS 31–19) as inferred from planktonic foraminiferal and calcium carbonate records     

Iván Hernández‐Almeida  Francisco Javier Sierro  José‐Abel Flores  Isabel Cacho  Gabriel Michael Filippelli 《Boreas: An International Journal of Quaternary Research》2013,42(1):140-159

Marine sediments from the Integrated Ocean Drilling Project (IODP) Site U1314 (56.36°N, 27.88°W), in the subpolar North Atlantic, were studied for their planktonic foraminifera, calcium carbonate content, and Neogloboqudrina pachyderma sinistral (sin.) δ¹³C records in order to reconstruct surface and intermediate conditions in this region during the Mid‐Pleistocene Transition (MPT). Variations in the palaeoceanography and regional dynamics of the Arctic Front were estimated by comparing CaCO₃ content, planktonic foraminiferal species abundances, carbon isotopes and ice‐rafted debris (IRD) data from Site U1314 with published data from other North Atlantic sites. Site U1314 exhibited high abundances of the polar planktonic foraminifera N. pachyderma sin. and low CaCO₃ content until Marine Isotope Stage (MIS) 26, indicating a relatively southeastward position of the Arctic Front (AF) and penetration of colder and low‐salinity surface arctic water‐masses. Changing conditions after MIS 25, with oscillations in the position of the AF, caused an increase in the northward export of the warmer North Atlantic Current (NAC), indicated by greater abundances of non‐polar planktonic foraminifera and higher CaCO₃. The N. pachyderma sin. δ¹³C data indicate good ventilation of the upper part of the intermediate water layer in the eastern North Atlantic during both glacial and interglacial stages, except during Terminations 24/23, 22/21 and 20/1. In addition, for N. pachyderma (sin.) we distinguished two morphotypes: non‐encrusted and heavily encrusted test. Results indicate that increases in the encrusted morphotype and lower planktonic foraminiferal diversity are related to the intensification of glacial conditions (lower sea‐surface temperatures, sea‐ice formation) during MIS 22 and 20.  相似文献   

Growth and feeding patterns of European anchovy (Engraulis encrasicolus) early life stages in the Aegean Sea (NE Mediterranean)     

Ignacio A. Catalán  Arild Folkvord  Isabel Palomera  Gemma Quílez-Badía  Fotini Kallianoti  Anastasios Tselepides  Argyris Kallianotis 《Estuarine, Coastal and Shelf Science》2010

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Enzymatic activity in the rhizosphere of Spartina maritima: potential contribution for phytoremediation of metals   总被引：2，自引：0，他引：2  

Reboreda R  Caçador I 《Marine environmental research》2008,65(1):77-84

Extracellular enzymatic activity (EEA) of five enzymes (peroxidase, phenol oxidase, beta-glucosidase, beta-N-acetylglucosaminidase and acid phosphatase) was analysed in sediments colonised by Spartina maritima in two salt marshes (Rosário and Pancas) of the Tagus estuary (Portugal) with different characteristics such as sediment parameters and metal contaminant levels. Our aim was a better understanding of the influence of the halophyte on microbial activity in the rhizosphere under different site conditions, and its potential consequences for metal cycling and phytoremediation in salt marshes. Acid phosphatase and beta-N-acetylglucosaminidase presented significantly higher EEA in Rosário than in Pancas, whereas the opposite occurred for peroxidase. This was mainly attributed to differences in organic matter between the two sites. A positive correlation between root biomass and EEA of hydrolases (beta-glucosidase, beta-N-acetylglucosaminidase and acid phosphatase) was found, indicating a possible influence of the halophyte in sediment microbial function. This would potentially affect metal cycling in the rhizosphere through microbial reactions.  相似文献