Distribution and abundance patterns of flatfishes in the Sado estuary, Portugal

The flatfish community of the Sado estuary was studied based on beam trawl catches in six sampling areas. Temperature and salinity were recorded during surveys and sediment composition was determined at each sampling area. A total of 12 species were identified (1 Bothidae, 1 Pleuronectidae, and 10 Soleidae).Dicologoglossa hexophthalma (Bennett 1831),Microchirus ocellatus (Linnaeus 1758), andSynaptura lusitanica (Capello 1868) were new records to this estuarine system.Monochirus hispidus Rafinesque, 1814, was the most abundant species (about 80% of the total individuals caught). Community structure reflected both spatial and temporal patterns. A longitudinal abundance pattern was noticed with some species much more abundant in outer estuarine areas, namelyM. hispidus, Arnoglossus laterna (Walbaum 1792), andBuglossidium luteum (Risso 1810), while others, such asSolea solea (Linnaeus 1758) andSolea senegalensis Kaup, 1858, presented the highest densities in inner areas. Besides temperature and salinity gradients, species distribution was also influenced by sediment composition. Seasonal variation was mainly determined by the different periods of juvenile peak abundance according to the species which emphasize the role of the estuary as a nursery ground for several flatfish species.     

Analytical approximate wave form for asymmetric waves

A simple analytical formulation that reproduces a skewed, nonlinear near-bed wave orbital velocity is presented. It contains four free parameters, where two are solely related to the velocity and acceleration skewnesses. The equation is compared with other models and is validated against field and laboratory experiments. The results reveal that it can simulate a wide range of nonlinear wave shapes, reproducing satisfactorily the measured nonlinear wave particle velocity. Also, the new expression overcomes some limitations of the other models. The new formulation is therefore capable of being used in many engineering applications that require the use of representative wave forms.     

Contrasts in genetic structure and historical demography of marine and riverine populations of Atherina at similar geographical scales

In this paper, we compare the genetic structure and the historical demography of two populations of the sand smelt Atherina boyeri from the rivers Tagus and Mondego (Portugal) with two groups of samples of the closely related marine Atherina presbyter collected on the shore at comparable latitudes. A. presbyter is a pelagic marine inshore fish, while A. boyeri is typically found in coastal lagoons, estuaries and freshwaters bodies. Analysis of mtDNA control region sequences showed that the marine A. presbyter did not display signs of genetic differentiation between sites some hundreds of kilometers apart. On the contrary, A. boyeri showed clear differences between populations. The populations of A. boyeri showed a much lower genetic diversity and younger coalescence times when compared with A. presbyter. We suggest that these differences reflect the interplay between differences in ecology between the two species and the historical impact of the glaciations. While A. presbyter likely moved to the south evading the cold periods, A. boyeri probably went extinct and its populations in Western Europe are recent recolonizations from western Mediterranean refugia.     

Post-Jurassic tectono-sedimentary evolution of the Northern Lusitanian Basin (Western Iberian margin)

Seismic reflection and well stratigraphic data are used to investigate the post‐Jurassic evolution of the Northern Lusitanian Basin, offshore west Iberia. Stratigraphic correlations between 11 exploration wells were attained in order to characterize the variations in depositional facies associated with salt tectonics. Latest Triassic–Hettangian salt, which generated multiple salt pillows during the Jurassic rifting, was reactivated after the early Aptian in two main phases. The first phase stretches from the late Turonian to the Maastrichtian. The second relates to Miocene tectonic inversion. The compression of the post‐salt overburden caused the amplification of Jurassic detachment folds, forming barriers to the westward progradation of sediment into distinct salt‐withdrawal sub‐basins. Particularly during the Miocene, thin‐skinned overburden shortening was accommodated by growing salt structures that suffered thrusting and extrusion. This structural style contrasts with that of salt‐scarce areas where a simple westerly tilted, fault‐bounded monocline was generated.     

Elemental and Single Particle Aerosol Characterisation at a Background Station in Kazakhstan

Aerosol sampling in Kazakhstan was performed at a remote astronomical observatory in the Tien Shan mountain region. The background character of the site was considered by comparing the elemental concentrations, obtained by Energy Dispersive X-Ray Fluorescence (EDXRF), with those reported for other remote stations. On the basis of the variability of the elemental concentrations and the source of origin, the elements could be classified into two main groups. These findings, complemented with enrichment factor calculations revealed the first group of elements to be originating mainly from local sources, and the second group to be related to long-range transport of anthropogenic aerosol. Automated individual particle analysis by electron probe X-ray microanalysis (EPXMA) and subsequent cluster analysis resulted in the identification of 12 distinct aerosol particle types. Relative particle type abundances were converted to absolute abundances by estimating the particle number concentrations for the detected particles, exploring the seasonal particle variation. Based on the absolute abundances, a strong seasonal pattern was found for Si-Al-Fe-, Si-, Ca-S-Si-, Ca-Si-, Fe-Si- and Ti-Si-rich particles. These particle types can mainly be attributed to the local soil source. For most of the remaining particle types, a completely different seasonal trend was found, which can be related to anthropogenic emissions. Their abundance in winter can be related to long-range transport of anthropogenic aerosols. As a result, these data can be representative for the Tien Shan site and may be useful to climate modellers and environmentalists.     

Traditional fisherfolk and no-take protected areas: The Peixe Lagoon National Park dilemma

This study challenges the ‘National Park’ as the appropriate management model for the Peixe Lagoon area in southern Brazil through an investigation of local fisherfolk livelihoods and traditional ecological knowledge. We argue that top-down management policies implemented through a non-participatory process, which have resulted in conflict between government officials and fisherfolk, disregarded the fisherfolk’s cultural practices and particular knowledge, thereby violating their rights as traditional people. Multiple suggestions are provided to achieve environmental conservation schemes without compromising the local traditional fishing livelihoods.     

The effects of sample scheduling and sample numbers on estimates of the annual fluxes of suspended sediment in fluvial systems

Since the 1970s, there has been both continuing and growing interest in developing accurate estimates of the annual fluvial transport (fluxes and loads) of suspended sediment and sediment‐associated chemical constituents. This study provides an evaluation of the effects of manual sample numbers (from 4 to 12 year^?1) and sample scheduling (random‐based, calendar‐based and hydrology‐based) on the precision, bias and accuracy of annual suspended sediment flux estimates. The evaluation is based on data from selected US Geological Survey daily suspended sediment stations in the USA and covers basins ranging in area from just over 900 km² to nearly 2 million km² and annual suspended sediment fluxes ranging from about 4 Kt year^?1 to about 200 Mt year^?1. The results appear to indicate that there is a scale effect for random‐based and calendar‐based sampling schemes, with larger sample numbers required as basin size decreases. All the sampling schemes evaluated display some level of positive (overestimates) or negative (underestimates) bias. The study further indicates that hydrology‐based sampling schemes are likely to generate the most accurate annual suspended sediment flux estimates with the fewest number of samples, regardless of basin size. This type of scheme seems most appropriate when the determination of suspended sediment concentrations, sediment‐associated chemical concentrations, annual suspended sediment and annual suspended sediment‐associated chemical fluxes only represent a few of the parameters of interest in multidisciplinary, multiparameter monitoring programmes. The results are just as applicable to the calibration of autosamplers/suspended sediment surrogates currently used to measure/estimate suspended sediment concentrations and ultimately, annual suspended sediment fluxes, because manual samples are required to adjust the sample data/measurements generated by these techniques so that they provide depth‐integrated and cross‐sectionally representative data. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.