Spatial variation in river runoff into a coastal area — An ecological approach

Carbon and nitrogen stable isotopes were used to investigate spatial variation in terrestrial particulate organic matter (POM) input to a coastal area off the Tagus river estuary. Isotopic variation in higher trophic level organisms was also examined, along the coast. This study was carried out in late summer, after a period of 3 months of low river flow. The overall aim was to determine if under such conditions the coastal area is enriched by the river plume and, particularly, if lower secondary productivity should be expected in some areas. Spatial variation was detected as a gradient of decreasing terrestrial input with increasing distance from the river. It was concluded that terrestrial carbon input was also incorporated into higher trophic levels and that organisms with lower mobility are more sensitive to the gradient in terrestrial input. Even in low flow conditions the whole fishing area remained under the influence of the river plume, which still accounted for 24% of the total POM 30 km from the river mouth. Additionally, δ¹⁵N values indicated pollution input from the river Tagus.     

A software tool for monitoring legal minimum length of landings: Case study of a fishery in southern Spain

The regulation of minimum legal size (MLS) of catches is a tool widely applied in the management of fisheries resources, although the MLS does not always coincide with the length at first maturity (LFM). The optimization of this management tool requires a series of quality control in fish markets and transportation. A software application has been developed to make the control of the landings of several target species easier and faster. In order to test and make this tool operational, six species of commercial interest were selected: four species of fish and two species of bivalves. It is proposed to estimate the proportion of illegal specimens in the studied lot from the proportion of illegal individuals found in the samples taken from this lot. The input data for the application are the minimum legal size (MLS) of the species and the total length (TL) of each specimen sampled. The output data is a statistical summary of the percentage of specimens of size less than the legal minimum (TL≤MLS) within different confidence intervals (90%, 95% and 99%). The software developed will serve as a fast, efficient and easy to manage tool that allows inspectors to determine the degree of compliance on MLS control and to make a decision supported by statistical proof on fishing goods.     

Determination of turbidity patterns of the Zhujiang estuarine region,South China,using satellite images and a GIS approach

Landsat MSS images and SPOT HRV data were employed to map the changes in turbidity levels in the Zhujiang estuarine region, South China, during the dry season in the period 1973–1987 at low and high tides. Analysis of turbidity trends and changes in the spatial pattern of high turbidity class was carried out with a GIS software—IDRISI. It was concluded that with the use of OVERLAY and RECLASS functions in the GIS approach a large number of turbidity maps could be easily compared and the turbidity trend determined. The GIS approach further permitted evaluation of the importance of such factors as water depths, mean tidal differences, and water salinity to sedimentation in the study region.     

Predictions for the clustering properties of the Lyman-alpha forest – I. One-point statistics

We present predictions for the one-point probability distribution and cumulants of the transmitted QSO flux in the high redshift Lyman- α forest. We make use of the correlation between the Lyman- α optical depth and the underlying matter density predicted by gravitational instability theory and seen in numerical hydrodynamic simulations. We have modelled the growth of matter fluctuations using the non-linear shear‐free dynamics, an approximation which reproduces well the results of perturbation theory for the cumulants in the linear and weakly non-linear clustering regime. As high matter overdensities tend to saturate in spectra, the statistics of the flux distribution are dominated by weakly non-linear overdensities. As a result, our analytic approach can produce accurate predictions, when tested against N -body simulation results, even when the underlying matter field has root-mean-square fluctuations larger than unity. Our treatment can be applied to either Gaussian or non-Gaussian initial conditions. Here we concentrate on the former case, but also include a study of a specific non-Gaussian model. We discuss how the methods and predictions we present can be used as a tool to study the generic clustering properties of the Lyman- α forest at high redshift. With such an approach, rather than concentrating on simulating specific cosmological models, we may be in a position to directly test our assumptions for the Gaussian nature of the initial conditions, and the gravitational instability origin of structure itself. In a separate paper we present results for two-point statistics.     

Secular Variation in the Composition of Basalts: an Index to Mantle Evolution

At the same Mg-number, a decrease is observed in the averagecontent of Ni, Co, and Cr in basalts between 2.5 and 2.0 b.y.Such decreases can be accounted for by smaller degrees of meltingin the mantle in response to falling geotherms. In terms ofpartially compatible (e.g. Ti, Zr, Nb, Y) and incompatible elements(e.g. Rb, Sr, Ba), Archean basalts are similar to modern island-arcbasalts although they are relatively enriched in Th and Zr anddepleted in Al. The upper concentration limit of partially compatibleand incompatible elements increases in basalts between 2?5 and1.0 b.y. Basalts with large concentrations of these elementsdo not appear to have been produced during the Archean and becomeimportant in the geologic record only after 1?0 b.y. ago. Varyingdegrees of melting, fractional crystallization, or crustal contaminationare not capable of accounting for these changes, and an increasingimportance of enriched mantle sources seems necessary. A greater availability of enriched mantle sources after theArchean may reflect recycling of ancient enriched mantle orcontinental sediments into the mantle during catastrophic continentalgrowth at 2.7 b.y.     

Os Isotopes and the Origin of the Tasmanian Dolerites

New Os isotope data obtained for oxides separated from samplesof the Jurassic dolerites of Tasmania (Australia) are used toconstrain the petrogenesis of the Ferrar continental flood basaltprovince. It is proposed here that the unradiogenic initialOs ratio (¹⁸⁷Os/¹⁸⁸Os = 0·145 ± 0·049 2     

Winter severity in Europe: The fourteenth century

The fourteenth century is known to include a period of winter cooling in Central and Western Europe, but its timing and magnitude are not clearly established. An attempt to obtain a coherent picture from verified documentary evidence yielded 2133 records from a region covering Central Europe and Northern Italy, mostly originating from the Monumenta Germaniae Historica. Temperatures were assessed using semi-quantitative indices on the basis of proxy information on snow-cover, ice and untimely activity of vegetation. Results: A run of cold winters from 1303 to 1328 was followed by a run of average winters up to 1354. Then winter temperatures were extremely variable up to 1375. For the rest of the century they fluctuated somewhat below the average of the twentieth century. The pattern in the first five decades is compared to that in the Late Maunder Minimum (1675–1715). The possible role of forcing factors (variations in solar output, North Atlantic Deep Water formation) is briefly discussed.     

Elasticity of polycrystalline stishovite

Ultrasonic data for the velocities of SiO₂-stishovite have been determined as a function of pressure to 10 kbar at room temperature for polycrystalline specimens hot-pressed at pressures P = 120kbar and temperatures T = 900°C. These cylindrical specimens are 2 mm in diameter and 0.9–1.4 mm long and have a grain size less than 10 μm. Compressional and shear wave velocities were measured both parallel and perpendicular to the axis of pressing and were found to be isotropic at 10 kbar with ν_p = 11.0 ± 0.2km/sec andν_s = 6.9 ± 0.3km/sec; this shear velocit is substantially higher than that of Mizutani et al. (1972) perhaps due to the presence of crack orientations in their specimen which affected ν_s but not ν_p. The Murnaghan P-V trajectories calculated from the ultrasonic data [bulk modulus K_s = 2.5 ± 0.3Mbar and assuming (?K_s/?P)_T = 6 ± 2] are consistent with recent hydrostatic compression data and with the shock wave compression data above 600 kbar. The combined evidence from the data of the ultrasonic and hydrostatic compression techniques suggests that the most probable value of the bulk modulus of stishovite at zero pressure is close to the upper limit of the uncertainty of our ultrasonically determined value, K₀ = 2.7?2.8Mbar. Elasticity data for rutile-type oxides are not compatible with normal K_s-V₀ systematics perhaps due to the neglect of non-central forces in the lattice model. These new stishovite data would make it impossible to satisfy the elasticity-density data of the lower mantle using an oxide mixture with either olivine or pyroxene stoichiometry.     

A procedure for identifying significant environmental aspects in sea ports

A new methodology has been designed to identify and rank the significant environmental aspects in sea ports. The main objective of the Strategic Overview of Significant Environmental Aspects (SOSEA) is to help port managers to identify significant environmental aspects and to reinforce the awareness about them in order to prioritise work in environmental management. Developed in close collaboration with port environmental managers and tested in a set of ports, it is a user-friendly tool that can be applied in approximately half a working day. It is based on ISO 14001 vocabulary and requirements and it can be considered as the base for the implementation of any Environmental Management System for port communities.