Differential reproductive strategies of two bivalves in the Dutch Wadden Sea

Cerastoderma edule and Mya arenaria are two common bivalve species in European waters. Longevity and maximum size are much greater in the latter species. Because comparison of species life-history strategies states that a long life span (i.e. high annual survival) generally goes with lower fecundity, we hypothesise that reproductive output would be lower in M. arenaria than in C. edule. In the present paper, we studied the reproductive strategies of these two species in an intertidal and a subtidal area of the western Dutch Wadden Sea, by following seasonal changes in absolute and relative weights of somatic and gonadal tissues in these bivalves. Starting of spawning was similar in the two species, around May, except for intertidal M. arenaria, which initiated spawning in August. Individual energy investment in reproduction was similar for the two species but, unlike M. arenaria, C. edule spawned completely, releasing all energy of gonadal mass in the form of gametes. Mya arenaria used the gonad not only for reproduction but also for storage. In the intertidal area, we found a trade-off between longevity and reproduction, i.e. maximum reproductive output (expressed as a proportion of body mass) was higher in C. edule than in M. arenaria. However, since body size is larger and life span longer in M. arenaria than in C. edule, mean lifetime reproductive output per individual must be higher in the first than in the latter. Based on the differences in reproductive strategies of these two species, we hypothesise that the negative effects of warming climate on bivalve population dynamics in the Wadden Sea will be stronger in C. edule than in M. arenaria.     

Seismic hazard analysis in zones of time and space interdependence: An application to São Miguel Island,Azores

The Azores Islands are located in the mid-Atlantic region near the triple junction where the Euro-Asiatic-African-American plates join together. Seismic activity in the area is very high, as can be observed either from historical events since the fifteenth century, from present day microseismicity, and from direct and indirect measurements of recent tectonic deformation. Volcanic activity is also present throughout the region. All available information, even data exhibiting low quality, was used to develop hazard models of São Miguel Island. Source zones were established based on both the global tectonic behaviour of the region and on the local active fault structures. Recurrence laws for São Miguel Island, for which historical information seemed quite incomplete, were obtained from the large events in the entire archipelago and from their remarkable pattern of time and space dependence, and complimented by information on long-term fault deformation (for the longer recurrence periods) and on high precision instrumental network (for the very short recurrence periods). Attenuation laws were derived from data on events felt and/or recorded in the Island. Hazard maps were obtained through a modified version of McGuire's algorithm for several geometries of source areas and results compared with the maximum observed intensity of historical events.     

The Amazon river breeze and the local boundary layer: I. Observations

Observations of the diurnal evolution of the planetary boundary layer over the Amazon rain forest, made at sites close to the confluence of the Solimões and Negro rivers (approximately at 3°S, 60°W) near Manaus, Amazonas, Brazil, show the existence of a diurnal rotation of the wind near the surface and the frequent presence of low-level nocturnal wind maxima. These circulations are shown to be plausibly explained as elements of a river and land breeze circulation induced by the thermal contrast between the rivers and the adjacent forest.     

Evolution of polycyclic alkanes in the Espirito Santo Basin

The distributions of polycyclic alkanes were monitored in a Neocomian sequence (well 1-ESS-34) from the Espirito Santo Basin, southeast Brazil. The profiles included, apart from regular hopanes, significant concentrations of 18α(H), 28,30-bisnorhopane and subordinate amounts of gammacerane. Sterane concentrations, normally with hopane/sterane <5, were compatible with other geochemical data indicating a predominantly planktonic/microbial source of the deposited organic matter. Sample maturities ranged from very immature to the onset of oil generation, allowing biomarker distributions to be followed along a broad maturation range. The ability of certain molecular ratios (e.g. C₂₇ 17α(H)/17β(H)hopanes) to reflect a maturity sequence with depth in the closely-spaced strata of the immature upper levels (Jiquiá Stage) showed the value of molecular techniques over classical geochemical methods (e.g. vitrinite reflectance) for the study of immature sequences. The presence in the oils of southern Espirito Santo of 28,30-bisnorhopane, gammacerane and methyl steranes in similar concentrations as in extracts of the deepest levels of the 1-ESS-34 well qualify the Jiquia Stage as the probable source rock of oils accumulated in the basin.     

Aquifer development planning to supply a seaside resort: a case study in Goa,India

Using the hydrogeological and socio-economic data derived from a European Commission research project on the measurement, monitoring and sustainability of the coastal environment, two optimization models have been applied to satisfy the future water resources needs of the coastal zone of Bardez in Goa, India. The number of tourists visiting Goa since the 1970s has risen considerably, and roughly a third of them go to Bardez taluka, prompting growth in the tourist-related infrastructure in the region. The optimization models are non-linear mixed integer models that have been solved using GAMS/DICOPT++ commercial software. Optimization models were used, firstly, to indicate the most suitable zones for building seaside resorts and wells to supply the tourist industry with an adequate amount of water, and secondly, to indicate the best location for wells to adequately supply pre-existing hotels. The models presented will help to define the optimal locations for the wells and the hydraulic infrastructures needed to satisfy demand at minimum cost, taking into account environmental constraints such as the risk of saline intrusion.

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Résumé A l’aide de données hydrogéologiques et socio-économiques, dérivées d’un projet de recherche de la Commission Européenne sur l’étude, la surveillance et la durabilité de l’environnement c?tier, deux modèles d’optimisation ont été appliqués en vue de satisfaire les besoins futurs en ressources en eau de la zone c?tière de Bardez au Goa en Inde. Le nombre de touristes qui visitent le Goa depuis les années 70 a considérablement augmenté et environ un tiers d’entre eux se rend à Bardez taluka, ce qui encourage la croissance des infrastructures liées au tourisme dans la région. Les modèles d’optimisation sont des modèles non linéaires mixtes en nombres entiers qui ont été résolus en utilisant le logiciel commercial GAMS/DICOPT++. Les modèles d’optimisation ont été utilisés pour indiquer premièrement les zones les plus appropriées pour construire des stations balnéaires et des puits pour approvisionner en quantité d’eau suffisante l’industrie touristique, et deuxièmement pour indiquer la meilleure localisation de puits pour l’alimentation des h?tels préexistants. Les modèles présentés aideront à définir les localisations optimales des puits et des infrastructures hydrauliques nécessaires à la satisfaction de la demande à un co?t minimum, tout en prenant en compte les contraintes environnementales, tel que le risque d’intrusion saline.

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Resumen Se han aplicado dos modelos de optimización en base a datos socio-económicos e hidrogeológicos derivados de un proyecto de investigación de la Comisión Europea sobre medición, monitoreo y sostenibilidad del ambiente costero para satisfacer las necesidades futuras de recursos hídricos de la zona costera de Bardez en Goa, India. El número de turistas que visita Goa desde la década de 1970′s ha subido considerablemente y cerca de un tercio de ellos van a Bardez taluka impulsando el crecimiento en la infraestructura turística de la región. Los modelos de optimización son modelos de números enteros mixtos no-lineales que se han resuelto usando el programa comercial GAMS/DICOPT++. Los modelos de optimización se usaron, primero para indicar las zonas más adecuadas para la construcción de centros de diversión en las márgenes del océano y pozos para abastecer la industria turística con una adecuada cantidad de agua, y segundo, para indicar la mejor localización de pozos para el abastecimiento de hoteles pre-existentes. Los modelos que se presentan ayudarán a definir las localizaciones óptimas para los pozos y las infraestructuras hidráulicas necesarias para satisfacer la demanda al mínimo costo, tomando en consideración restricciones ambientales tal como el riesgo de intrusión salina.

     

Scalar advection schemes for ocean modelling on unstructured triangular grids

Several schemes for scalar advection on unstructured triangular grids are assessed for possible use in ocean modelling applications. Finite element, finite volume and finite volume–element approaches are evaluated. A series of tests, including a numerical order of convergence analysis, idealized rotating cone and cylinder experiments, and transport of a tracer through the Stommel Gyre representation of ocean basin-scale circulation, are carried out. Volume element Eulerian–Lagrangian and third-order Runge-Kutta discontinuous Galerkin schemes are recommended for use in tracer studies. Taylor–Galerkin and second-order Runge–Kutta discontinuous Galerkin are found to be robust and accurate second-order schemes. When positivity is required, a fluctuation redistribution scheme was found to be an easily implemented, accurate, and computationally efficient approach. Responsible editor: Phil Dyke     

Lateritic nickel deposits of Brazil

Many nickel deposits are known in Brazil, accounting for about 350 · 10⁶ tons of ore with an average of 1.5% Ni. All are of the lateritic type. These deposits are scattered throughout the country, being rarer in the Northeastern Region and in the South, below 25 °S latitude. They are mainly associated with mafic-ultramafic massifs of large dimensions and ultramafic alkaline complexes, and occur in climatic regions of contrasting seasons. The weathering profile developed over the fresh rock consists, from bottom to top, of the following horizons: altered rock, coarse saprolite, argillaceous saprolite, ferruginous saprolite and lateritic overburden. The thickness of each horizon varies from one deposit to another, the whole profile generally exceeding 20 m. The saprolitic horizons with inherited minerals (serpentine, chlorite) or neoformed minerals (smectites) constitute the silicated nickel ore and are thicker were climatic conditions are drier; the ferruginous upper horizons made up of iron oxide-hydroxides are more developed in more humid regions. In Brazil, the silicated ore generally prevails over the oxidized ore. The main Ni-bearing minerals are serpentine, smectite, garnierite and goethite. The lateritic nickel deposits of Brazil may be correlated with two erosion surfaces, corresponding to the Sul Americano (Lower Tertiary) and Velhas (Upper Tertiary) levelling cycles. The degree of dismantling of the higher and more ancient surface and the consequent development of the Velhas Surface control the position of the nickel accumulation in the landscape. Thus, the deposits may be found either in the lowlands or in the highlands, where they are always covered by a silcrete layer. The alteration profiles in the Brazilian lateritic nickel deposits are broadly similar to those described elsewhere in the world. However, they present two characteristic features: the silicated ore prevails over the oxidized ore, and a silicified layer covers the profies developed on the highlands.     

地下水水源保护区范围计算的KLF法及其在徐州张集地区的应用

详细介绍了地下水水源保护区范围的计算方法:Krijgsman-Lobo-Ferreira(KLF)法,分别推导出了正水流梯度方向、负水流梯度方向和垂直于地下水流方向保护区范围的计算公式,并就方法的适用性及参数取值等问题进行了探讨.在徐州张集地区应用的结果表明,KLF法提供了一种计算地下水保护区范围的便捷、科学、有效的方法,计算结果对于确定地下水源保护区范围及有效保护地下水源具有实际意义.