On the presence of <Emphasis Type="Italic">Stephanodiscus niagarae</Emphasis> Ehrenberg in central Mexico

Stephanodiscus niagarae is frequently reported from late Pleistocene (>10,000 yr BP) sediments in central Mexico, with lower abundances through the Holocene. Its presence in Holocene and modern environments in central Mexico was not well documented until our study, where we report on three populations of S. niagarae, one middle Holocene population with particularly high abundance from the Upper Lerma Basin, and two modern sites, Valle de Bravo and Santa Elena. The three sites are located in the same geographical area, in the State of Mexico. The fossil material dates to ca. 6600–4900 yr BP, with S. niagarae reaching up to 90% of the diatom counts. Stephanodiscus niagarae is present in association with Fragilaria pinnata, F. brevistriata, and Aulacoseira granulata. In Valle de Bravo (ca. 30 m deep) S. niagarae is present in very low numbers in water column and surface sediments samples (<1%); the diatom assemblage is dominated by Fragilaria crotonensis in association with A. granulata, A. granulata var. curvata and Cyclotella ocellata. In Santa Elena, a shallow, intermittent irrigation channel, S. niagarae is the second most abundant alga; the diatom assemblage is dominated by S. niagarae in association with A. granulata, A. granulata var. curvata and F. crotonensis. Both modern sites show a trend to eutrophy and these diatom assemblages are taken as indicative of this trend. It is suggested researchers should be cautions when the presence of S. niagarae in sedimentary records is taken as indicative of deep waters conditions, as the present data show that this species can thrive in rather shallow environments in Mexico.     

Competitive policies for commercial sea ports in the EU

The globalisation of the economy and the need for sustainable growth are having a strong influence on international sea freight transport and its infrastructures. Commercial sea ports, faced with the loss in ‘loyalty’ of their traffic and the appearance of ‘new rules in the game’, are developing new strategies in order to achieve the loyalty of their clients. The present paper is a reflection on the findings generated in recent years in the area of competitive port policies. The main focus is on the formulation of commercial and technological strategies, the new legislative framework and its consequences for the European Union in the context of the future ‘Common Ports Policy’.     

Life cycle of Marphysa sanguinea (Polychaeta: Eunicidae) in the Venice Lagoon (Italy)

The life cycle of a brackish water population of Marphysa sanguinea (Polychaeta Eunicidae), from the Venice Lagoon (Italy), was investigated from April 1993 to August 1994. Marphysa sanguinea is a large‐sized gonochoric species with annual iteroparous strategy and synchronous spawning at population level. The sex‐ratio was close to 1:1. There were no morphological differences between males and females and spawning occurred without epitokal metamorphosis. The gonadial activity was maximum during summer period in both sexes. From May to September in the females, the greater number of immature oocytes could be observed; starting from November immature oocytes decreased and progressively those with a wider diameter increased in number. Spawning took place in April–May and generally not all eggs were spawned, a small proportion being kept as a reserve material for the following gamete production. The pelagic phase (trochophore and metatrochophore stages) was short (2–3 days). The reduction in the dispersal phase, together with the development of a strong anterior musculature, brought to an early acquisition of the benthic habit, which was attained with the construction of the mucous tube inside of which the larva lived. The results highlighted that colonization of brackish environments took place thanks to morphological and physiological features that allow this species to live in a sediment layer characterized by the stability of the physical and chemical characteristics of the substratum.     

Acritarchs of Las Ventanas Formation (Ediacaran, Uruguay): Implications for the timing of coeval rifting and glacial events in western Gondwana

Acritarchs and other organic-walled microfossils occurring in siltstones of the Las Ventanas Formation (Quebrada de Viera and El Perdido members) are systematically described and illustrated. The assemblage includes the following species: Leiosphaeridia tenuissima, Leiosphaeridia minutissima, Lophosphaeridium sp., Soldadophycus bossii, Soldadophycus major, Soldadophycus sp. and Vendotaenia antiqua. The microflora is characterized by low diversity (six species), dominance of L. tenuissima, absence of acanthomorphic acritarchs, and relatively large size of sphaeromorphs, reaching 400 μm in diameter. A number of species are shared with acritarch assemblages preserved in the overlying Arroyo del Soldado Group. Differences between assemblages include the occurrence of abundant Bavlinella faveolata and small size of spheroids in the Arroyo del Soldado Group. The assemblage occurring in Las Ventanas Formation is assigned to the Ediacaran Leiosphere Palynoflora, which spans the interval between the base of the Ediacaran (end of the Marinoan Glaciation, 635 Ma) and the termination of the Gaskiers Glaciation (582 Ma). An early Ediacaran age between 615 and 579 Ma is also supported by available radiometric ages. An extensional setting for Las Ventanas basin is suggested on the basis of the bimodal, synsedimentary volcanism, strong palaeorelief, great thickness of alluvial fan conglomerates and the evolution from continental to open marine environments. Diamictites occurring in the Quebrada de Viera Member are described for the first time, including associated dropstones which suggest a glacial origin. If confirmed, this would be one more example of the association between rifting and glaciation in the Neoproterozoic, coeval with a low-diversity, high-abundance acritarch microflora. A causal relationship between these tectonic, climatic and biologic events is discussed.     

Possibilities of using silicate rock powder:An overview

This study evaluates the on use of crushed rocks(remineralizers)to increase soil fertility levels and which contributed to increase agricultural productivity,recovery of degraded areas,decontamination of water,and carbon sequestration.The use of these geological materials is part of the assumptions of rock technology and,indirectly,facilitates the achievement of sustainable development goals related to soil management,climate change,and the preservation of water resources.Research over the past 50 years on silicate rocks focused on soil fertility management and agricultural productivity.More recently,the combined use with microorganisms and organic correctives have shown positive results to mitigate soil degradation;to expand carbon sequestration and storage;and to contribute to the adsorption of contaminants from water and soil.In this article we show results obtained in several countries and we show that this technology can contribute to the sustainability of agriculture,as well as to reverse global warming.Although mineral nutrients are released more slowly from these types of inputs,they remain in the soil for a longer time,stimulating the soil biota.In addition,they are a technology to soluble synthetic fertilizers replace,since the few nutrients derived from such inputs not consumed by plants are lost by leaching,contaminating groundwater and water resources.In addition,conventional methods rely heavily on chemical pesticides which cause damage to soil’s microfauna(responsible for the decomposition of organic matter and nutrient cycling)and the loss of organic carbon(in the form of dioxide),which is quickly dispersed in the atmosphere.Silicate rock powders are applied in natura,have long-lasting residual effects and reduce greenhouse gas emissions.     

Physical-hydraulic properties of tropical sandy-loam soil in response to rice-husk dust and cattle dung amendments and surface mulching

ABSTRACT

The effects of topsoil addition of rice-husk dust (RHD) and cattle dung (CD), alongside surface mulching with dry grasses/legume, on the infiltration characteristics and intrinsic structural properties of a deep, well-drained soil in southeastern Nigeria are assessed. Treatments are RHD-amended, CD-amended and “unamended”, each plot being either surface-mulched or left bare, with the unamended-bare plots as control. Amendments and mulch were applied at 20 t/ha equivalents. Their effects on the soil’s infiltration characteristics 7 months later were not evident; however, there was a tendency for differences: CD-amended ≥ RHD-amended ≥ unamended and surface-mulched ≥ bare-surface. By contrast, saturated hydraulic conductivity (K_s ) differed thus: CD-mulched ≥ unamended-mulched > the rest. Similar values were recorded for K_s (50.89 cm/h) and final infiltration rate (50.74 cm/h) only under CD-amended plots, which also showed the highest values (43.50 cm/h) for transmissivity of the soil. Soil penetrometer resistance was lowest in CD-amended plots (113.44 kPa) and highest in unamended plots (166.78 kPa). Topsoil addition of cattle dung and surface mulching could increase infiltration, though marginally, and permeability of coarse-textured tropical soils beyond the season of their application when their effects on soil structure have almost waned.     

A spectroscopic method for identifying terrestrial biocarbonates and application to Mars

Searching for traces of extinct and/or extant life on Mars is one of the major objectives for remote-sensing and in situ exploration of the planet. In previous laboratory works we have investigated the infrared spectral modifications induced by thermal processing on different carbonate samples, in the form of fresh shells and fossils of different ages, whose biotic origin is easily recognizable. The goal was to discriminate them from their abiotic counterparts. In general, it is difficult to identify biotic signatures, especially when the organisms inducing the carbonate precipitation have low fossilization potential (i.e. microbes, bacteria, archaea). A wide variety of microorganisms are implicated in carbonate genesis, and their direct characterization is very difficult to evaluate by traditional methods, both in ancient sedimentary systems and even in recent environments.In the present work we apply our analysis to problematic carbonate samples, in which there is no clear evidence of controlled or induced biomineralization. This analysis indicates a very likely biotic origin of the aragonite samples under study, in agreement with the conclusion previously reported by Guido et al. (2007) who followed a completely different approach based on a complex set of sedimentary, petrographic, geochemical and biochemical analyses. We show that our method is reliable for discriminating between biotic and abiotic carbonates, and therefore it is a powerful tool in the search for life on Mars in the next generation of space missions to the planet.     

Diffuse reflectance of altered olivine grains: Remote sensing detection and implications for Mars studies

The study of Mars linked to its climatic history, the presence of water and possible forms of life on the planet, are becoming more and more important in recent years. In this paper we present laboratory reflection measurements on olivine samples which are believed to be the product of alteration induced by their coexistence with water. The reflection spectra have been obtained in the wavelength range from 0.2 to and for different grain sizes; they exhibit, among various bands, some of which due to H₂O and OH^-, a characteristic absorption feature at about , whose emission wings at 0.56 and near have relative strengths which are size dependent and well correlated. The identification of such feature in the observed spectra of Mars would provide useful information about the grain size of the Martian regolith and, in association with other bands, also about the possible presence of olivine altered by water in the past.     

Topology and Dynamics of the 12 December 1980 Magnetic Cloud Event

In this work we have performed an analysis of the interplanetary magnetic field and plasma parameters associated with the 12th December 1980 shock–magnetic cloud event. The study was complemented by including a detailed analysis of the energetic particles fluxes, spectral indexes and directional information. Locally, the magnetic cloud had a latitude of 48°, longitude of 220° and a radius of 0.15 AU. The maximum approach of the ISEE-3 spacecraft to the magnetic cloud axis was 0.047 AU. Moreover, our results suggest that, when encountered by the spacecraft, the magnetic cloud was expanding at a rate of roughly r ₁/r ₀=1.5 (r ₁ is the final radius and r ₀ the initial one) and that it had been expanding during 59 hr. We have also found evidence which indicates that the particle injection inside the cloud depended on the particle energy and pitch angle. These features also suggest that the energetic particle bi-directional fluxes could not be produced by mirroring in the magnetic cloud feet. Instead we think that these fluxes could be generated by the intrinsic properties of the injection mechanism.     

MIDI observations of 1459 Magnya: First attempt of interferometric observations of asteroids with the VLTI

The Very Large Telescope Interferometer (VLTI) of the European Southern Observatory (ESO) can be used to obtain direct determination of the sizes and the albedos of asteroids. We present results of the first attempt to carry out interferometric observations of asteroids with the Mid Infrared Interferometric Instrument (MIDI) at the VLTI. Our target was 1459 Magnya. This is the only V-type asteroid known to exist in the outer main-belt, and its IRAS-albedo turns out to be rather low for an object of this taxonomic class. Interferometric fringes were not detected, very likely due to the fact that the flux emitted by the asteroid was lower than expected and below the MIDI threshold for fringe detection. However, by fitting the Standard Thermal Model to the N-band infrared flux measured by MIDI in photometric mode and to the visible absolute magnitude, obtained from quasi-simultaneous B- and V-band photometric observations, we have derived a geometric visible albedo of 0.37±0.06 and an effective diameter of 17±1 km. This new estimate of the albedo differs from that previously obtained by IRAS and is more consistent with the V-type taxonomic classification of 1459 Magnya.