Modelling nutrient mass balance in a temperate meso-tidal estuary: Implications for management     

João Magalhães Neto  Mogens René Flindt  João Carlos Marques  Miguel Ângelo Pardal 《Estuarine, Coastal and Shelf Science》2008

Although mitigation programmes have been implemented in huge eutrophied estuarine systems, satisfactory results are not always immediately achieved. External loadings are reduced but the nutrient pools still existing in the sediments (due to decades of external supply) start to deplete only slowly, to reach the lower steady state level related to the new external loading. In the Mondego Estuary, this situation could be seen from the mass balance calculations including different nutrient fractions (dissolved, SPM and bound in vegetation). Different nutrient fractions quantified over the year showed the retention capacity and supplying capacity of these estuarine systems, and also the seasonal dynamics those fractions can present. External loading of nitrogen was largely dominated by DIN, but after its incorporation by benthic primary producers nitrogen export occurred essentially as SPM-N. Phosphorus loading was dominated by SPM-P, but during warmer periods P-efflux increased DIP concentration inside the system and was afterwards exported through the outer boundary. Although nutrients bound in vegetation were not significant to total mass balance, depending on the occurrence of occasional macroalgal blooms, the vegetation fraction can significantly increase its contribution to the overall balance.  相似文献   

Rebuilding viable spawner patches of the overfished Spisula solida (Mollusca: Bivalvia): a preliminary contribution to fishery sustainability     

Joaquim  Sandra; Gaspar  Miguel B.; Matias  Domitilia; Ben-Hamadou  Radhouan; Arnold  William S. 《ICES Journal of Marine Science》2008,65(1):60-64

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High gene flow promotes the genetic homogeneity of the fish goby Pomatoschistus marmoratus (Risso, 1810) from Mar Menor coastal lagoon and adjacent marine waters (Spain)     

Carlos Vergara‐Chen  Mercedes González‐Wangüemert  Concepción Marcos  Ángel Pérez‐Ruzafa 《Marine Ecology》2010,31(2):270-275

The extreme environmental variability of coastal lagoons suggests that physical and ecological factors could contribute to the genetic divergence among populations occurring in lagoon and open‐coast environments. In this study we analysed the genetic variability of lagoon and marine samples of the sand goby, Pomatoschistus marmoratus (Risso, 1810) (Pisces: Gobiidae), on the SW Spain coast. A fragment of mitochondrial DNA control region (570 bp) was sequenced for 196 individuals collected in five localities: Lo Pagan, Los Urrutias and Playa Honda (Mar Menor coastal lagoon), and Veneziola and Mazarrón (Mediterranean Sea). The total haplotype diversity was h = 0.9424 ± 0.0229, and the total nucleotide diversity was π = 0.0108 ± 0.0058. Among‐sample genetic differentiation was not significant and small‐scale patterns in the distribution of haplotypes were not apparent. Gene flow and dispersal‐related life history traits may account for low genetic structure at a small spatial scale. The high genetic diversity found in P. marmoratus increases its potential to adapt to changing conditions of the Mar Menor coastal lagoon.  相似文献   

A description of chloride cell and kidney tubule alterations in the flatfish Solea senegalensis exposed to moderately contaminated sediments from the Sado estuary (Portugal)     

Pedro M. Costa  Sandra Caeiro  Mrio S. Diniz  Jorge Lobo  Marta Martins  Ana M. Ferreira  Miguel Caetano  Carlos Vale  T. ngel DelValls  M. Helena Costa 《Journal of Sea Research》2010,64(4):465-472

The effects of sediment-bound contaminants on kidney and gill chloride cells were surveyed in juvenile Solea senegalensis exposed to fresh sediments collected from three distinct sites of the Sado Estuary (Portugal) in a 28-day laboratorial assay. Sediments were analyzed for metallic contaminants, polycyclic aromatic hydrocarbons and organochlorines as well as for total organic matter, redox potential and fine fraction. The potential for causing adverse biological effects of each surveyed sediment was assessed by comparison of contaminant levels to available guidelines for coastal sediments, namely the Threshold Effects Level (TEL) and the Probable Effects Level (PEL). The Sediment Quality Guideline Quotient indices (SQGQ) were calculated to compare the overall contamination levels of the three stations. A qualitative approach was employed to analyze the histo/cytopathological traits in gill chloride cells and body kidney of fish exposed to each tested sediment for 0, 14 and 28 days. The results showed that sediment contamination can be considered low to moderate and that the least contaminated sediment (from a reference site, with the lowest SQGQ) caused lesser changes in the surveyed organs. However, the most contaminated sediment (by both metallic and organic xenobiotics, with highest SQGQ) was neither responsible for the highest mortality nor for the most pronounced lesions. Exposure to the sediment presenting an intermediate SQGQ, essentially contaminated by organic compounds, caused the highest mortality (48%) and the most severe damage to kidneys, up to full renal necrosis. Chloride cell alterations were similar in fish exposed to the two most contaminated sediments and consisted of a pronounced cellular hypertrophy, likely involving fluid retention and loss of mitochondria. It can be concluded that sediment contamination considered to be low or moderate may be responsible for severe injury to cells and parenchyma involved in the maintenance of osmotic balance, contributing for the high mortality levels observed. The results suggest that sediment-bound organic contaminants such as PAHs (polycyclic aromatic hydrocarbons) and PCBs (polychlorinated biphenyls) may be very toxic to the analyzed organs, especially the kidney, even when present in low-risk concentrations.  相似文献   

The Main Belt Comets and ice in the Solar System     

Colin Snodgrass  Jessica Agarwal  Michael Combi  Alan Fitzsimmons  Aurelie Guilbert-Lepoutre  Henry H. Hsieh  Man-To Hui  Emmanuel Jehin  Michael S. P. Kelley  Matthew M. Knight  Cyrielle Opitom  Roberto Orosei  Miguel de Val-Borro  Bin Yang 《Astronomy and Astrophysics Review》2017,25(1):5

We review the evidence for buried ice in the asteroid belt; specifically the questions around the so-called Main Belt Comets (MBCs). We summarise the evidence for water throughout the Solar System, and describe the various methods for detecting it, including remote sensing from ultraviolet to radio wavelengths. We review progress in the first decade of study of MBCs, including observations, modelling of ice survival, and discussion on their origins. We then look at which methods will likely be most effective for further progress, including the key challenge of direct detection of (escaping) water in these bodies.  相似文献   

Seasonal variations in lipid composition of the hydrothermal vent mussel Bathymodiolus azoricus from the Menez Gwen vent field     

Ana Colaço  Catarina Prieto  Ana Martins  Miguel Figueiredo  Virginie Lafon  Margarida Monteiro  Narcisa M. Bandarra 《Marine environmental research》2009,67(3):146-152

Specimens of the hydrothermal mussel Bathymodiolus azoricus collected in Menez Gwen hydrothermal vent field (NE Atlantic) during 2002–2003 were examined for feeding patterns variations through three seasons. The fatty acid profile and lipid classes of the mussels were studied, together with the MODIS/AQUA-derived near-surface chlorophyll a to test the hypothesis that surface productivity might be related to the feeding patterns of this species. The lipid levels showed pronounced seasonal fluctuations with the highest values occurring in January and August. Seasonal variations in lipid classes and fatty acid composition of neutral and polar lipids in the mussels are presented. Differences in the fatty acid profile of lipid classes in different seasons suggest that the higher energy requirements in summer and winter were supplied by bacterial biomarkers ω7 MUFA (monounsaturated fatty acids), whereas ω6 PUFA (polyunsaturated fatty acids) and NMI (non-methylene-interrupted) fatty acids predominated during the spring. The MODIS/AQUA data show marked seasonal variability and an anomalous peak during January of 2003, although this cannot be directly linked to lipid composition variation.  相似文献   

A weight of evidence approach for quality assessment of sediments impacted by an oil spill: The role of a set of biomarkers as a line of evidence     

Carmen Morales-Caselles  Inmaculada Riba  T. Ángel DelValls 《Marine environmental research》2009,67(1):31-37

In an attempt to incorporate both line of evidence (LOE) and classical weight of evidence (WOE) approaches for the assessment of sediment quality, a set of biomarkers were analyzed in target tissues of two invertebrate species after 28 days of exposure to sediments impacted by oil (derived from the tanker Prestige (2002)). The integration of biomarkers with sediment contamination, acute toxicity and benthic alteration parameters provides an “early warning” tool which not only indicates the environmental quality of an area, but also constitutes an advisory tool for potential ecological risks. The selected biomarkers provide information about the first biological responses due to the presence of contaminants in the environment providing predictable reports about further effects to the ecosystem. The present study demonstrates that the use of a set of biomarkers as part of a WOE approach designed to assess contaminated sediments contributes added value to the classical LOE and allows characterization of the environmental status of the studied area in a more precise and accurate way.  相似文献   

Sandy beach macrofaunal communities on the western coast of Portugal – Is there a steady structure under similar exposed conditions?     

Sílvia C. Gonalves  Pedro M. Anastcio  Miguel A. Pardal  Patrícia G.Cardoso  Susana M. Ferreira  Joo C. Marques 《Estuarine, Coastal and Shelf Science》2009,81(4):555-568

The structure of macrofaunal communities at two similar exposed sandy beaches on the western coast of Portugal was monitored for approximately 18 months by sampling all the beach area, from the shoreline to the base of the dunes. The beaches’ physical environment, as well as community density and composition, seasonal variations and the potential relationships between biological data and environmental parameters were studied. The two beaches had similar exposure to wave action, but differed in terms of sediment grain size, extent of the intertidal area, sediment moisture content and, especially, in the potential food availability in the form of allochthonous debris. Differences were observed with regard to the communities’ structure, namely regarding composition and relative contribution of the dominant species. Seasonality, especially temperature variations, and the interaction between seasons and the beach zones (supralittoral vs. intertidal) also had a strong influence on communities: controlling dominant species’ density and the horizontal distribution of the dominant species, and promoting a differential utilization of the beach by several resident macrofaunal animals. The present study allows the identification of key species in exposed sandy beaches of western Portugal and demonstrates that a steady community structure does not persist in the similarly exposed conditions observed, which may be mainly a response to distinct detritus subsidies, combined with differences in sediment grain size, sediment moisture content and extent of the intertidal area.  相似文献   

Characteristic friction coefficient and scale effects in oscillatory porous flow     

Dulce María Pérez-Romero  Miguel Ortega-Sánchez  Antonio Moñino  Miguel A. Losada 《Coastal Engineering》2009

This work presents a simple method to evaluate the performance of a porous breakwater when it is impinged with normal incidence by a non-breaking monochromatic wave train. It is based on: 1) a potential flow model for wave interaction with permeable structures and 2) a set of experimental tests on a rectangular porous structure with uniform granular distribution. A characteristic friction diagram is obtained considering wave energy balance in a control volume, minimising the error between the numerical model and the experimental results for the wave transmission coefficient. Results show that, for large breakwater widths, the reflection process reaches a saturation regime before the waves exit the structure at a distance from the seaside between the interval 0.2 < x/L < 0.45. For larger breakwater widths, the reflection coefficient is almost constant (except for “resonant” conditions) and wave transmission decreases exponentially. Under such conditions, the wave propagation through the porous medium depends on the relative diameter D/L and the porosity of the material; the dependence on the relative breakwater width B/L and the ratio diameter wave height D/H is weak. This diagram intends to be useful for preliminary engineering studies of breakwater's efficiency and performance and as an adequate selection criteria of the experimental stone diameter to minimize scale effects in laboratory studies.  相似文献   

Late pleistocene/early holocene environments and climates,fauna, and human occupation in the argentine altiplano     

Jorge Fernndez  Vera Markgraf  Hctor O. Panarello  Miguel Albero  Fernando E. Angiolini  Susana Valencio  Mirta Arriaga 《Geoarchaeology》1991,6(3):251-272

The Barro Negro site (23°S lat., 65°37′W long.) in the Altiplano (Puna) of northwestern Argentina contains a well stratified sequence of remains of Hippidion, the American extinct horse, camelids, and archaeological materials, which is the focus of this study. In addition to establishing a reliable chronology, paleoenvironmental information was obtained based on analyses of pollen and stable isotopes (oxygen and carbon) from bone and marl. The data indicate that Hippidion was present at the site between 12,000 and 10,000 yr B. P., at a time when Altoandean grasslands had expanded to lower elevations. By 10,000 yr B.P., when modern semi-arid sub-puna scrub had replaced the Altoandean grasslands, only camelids (Lama or Vicugna) were present, simultaneous with the first evidence of local human occupation. This suggests that a climatic shift from cool and moist (winter rain regime) to warm and dry (summer rain regime) conditions took place simultaneously with the disappearance of the American horse and the appearance of camelids and man.  相似文献