Deeply Penetrating Banded Zonal Flows in the Solar Convection Zone     

Howe R  Christensen-Dalsgaard J  Hill F  Komm RW  Larsen RM  Schou J  Thompson MJ  Toomre J 《The Astrophysical journal》2000,534(2):L163-L166

We discuss the spectrum arising from synchrotron emission by fast cooling (FC) electrons, when fresh electrons are continually accelerated by a strong blast wave, into a power-law distribution of energies. The FC spectrum has so far been described by four power-law segments divided by three break frequencies nusa相似文献   

Use of multimetric indices to classify estuaries with different hydromorphological characteristics and different levels of human pressure     

Chainho P  Chaves ML  Costa JL  Costa MJ  Dauer DM 《Marine pollution bulletin》2008,56(6):1128-1137

The assessment of estuaries based on benthic communities is widely used to determine impacts caused by human pressure and is one of the required tools for the implementation of the European Water Framework Directive (WFD). Our study compared multimetric approaches (B-IBI and TICOR) to assess the benthic condition of three Portuguese estuaries (Mondego, Tejo, and Mira rivers) with different levels of natural and human induced stress. Benthic community condition was classified into quality status categories of the WFD and compared for consistency with a priori status categories based upon physical-chemical criteria. Both multimetric indices discriminated equally well between locations classified above or below the good status category but were unable to provide good separation between other quality classes (high/good, moderate, poor/bad). Metrics included in these indices are greatly affected by natural stress and we recommend the development of habitat-specific thresholds to increase the discriminatory ability of any benthic condition index.  相似文献   

Impact of discards of beam trawl fishing on the nematode community from the Tagus estuary (Portugal)     

Franco MA  Steyaert M  Cabral HN  Tenreiro R  Chambel L  Vincx M  Costa MJ  Vanaverbeke J 《Marine pollution bulletin》2008,56(10):1728-1736

The impact of dead discards, originating from beam trawl fishing on the nematode community from the Tagus estuary was investigated in terms of vertical distribution of the dominant nematode groups. Sediment cores were collected from a mud-flat from the Tagus estuary. Crangoncrangon (Linnaeus, 1758) carcasses were added to the surface of the cores, simulating the settling of dead discards on the sediment. The vertical distribution of the dominant nematode groups was determined up to 4 cm deep at four different moments in time post deposition (0, 2, 4 and 6 h) and compared to control cores. The C.crangon addition to the sediment led to the formation of black spots and therefore oxygen depleted areas at the sediment surface. The Chromadora/Ptycholaimellus group, normally dominant at the surface layer, migrated downwards due to their high sensibility to toxic conditions. Sabatieria presented the opposite trend and became the dominant group at the surface layer. Since Sabatieria is tolerant to oxygen stressed conditions and high sulphide concentrations, we suggest that it migrated opportunistically towards an unoccupied niche. Daptonema, Metachromadora and Terschellingia did not show any vertical migration, reflecting their tolerance to anoxic and high sulphidic conditions. Our study showed that an accumulation of dead discards at the sediment surface might therefore alter the nematode community vertical distribution. This effect is apparently closely related to toxic conditions in the sediment, induced by the deposition of C.crangon at the sediment surface. These alterations might be temporal and reflect an adaptation of the nematode community to dynamic intertidal environments.  相似文献   

A 130 year record of pollution in the Suances estuary (southern Bay of Biscay): implications for environmental management     

Irabien MJ  Cearreta A  Leorri E  Gómez J  Viguri J 《Marine pollution bulletin》2008,56(10):1719-1727

Geochemical composition (Al, Zn, Pb, Cd, Cu, Ni, Cr and As) and foraminiferal assemblages in surface and core sediments were determined to assess the current situation and the recent environmental transformation of the Suances estuary (southern Bay of Biscay, Spain). Dating of the historical record has been achieved using isotopic analysis (²¹⁰Pb, ¹³⁷Cs) and two benchmark events such as the beginning of the mineral exploitation in the Reocín Pb-Zn deposits and the evolution of the chlor-alkali industry (inputs of Hg). Concentrations of Zn, Pb and Cd in both surface and core samples are remarkably higher than background values, reflecting the existence of significant amounts of polluted materials. The dramatic environmental impact of this pollution is clearly recorded by the change of the foraminiferal assemblages that even reach an afaunal stage during recent decades. Application of two different sets of Sediment Quality Guidelines confirm that they exert potential risk to the environment, and therefore if dredged they should need specific management measures.The results provide a reference database to monitor future environmental changes in the Suances estuary, particularly as regards the contaminated sediment storage and the re-colonization by autochtonous meiofauna.  相似文献   

Efficacy of adapted estuarine fish-based multimetric indices as tools for evaluating ecological status of the marine environment     

Henriques S  Pais MP  Costa MJ  Cabral H 《Marine pollution bulletin》2008,56(10):1696-1713

The assessment of ecological status of marine fish communities required by the marine strategy framework directive (MSFD) emphasises the need for fish-based ecological indices in marine waters. In this study we adapt five estuarine multimetric indices to the marine environment and apply them in three types of substrates, analysing the metrics responsible for the obtained patterns of ecological status. The results show inefficiency of the community degradation index (CDI) and the biological health index (BHI) in ecological status assessment and disagreement between the estuarine biotic integrity index (EBI), the estuarine fish community index (EFCI) and the transitional fish classification index (TFCI). Analysis of individual metrics suggests lack of representativeness and consideration for the particularities of each substrate’s typical fish communities. None of the tested indices were efficient on the marine environment, urging the need for new marine indices that account for differences between types of substrate and depth.  相似文献   

Comparative petroleum hydrocarbons levels and biochemical responses in mussels from hydrothermal vents (Bathymodiolus azoricus) and coastal environments (Mytilus galloprovincialis)     

Serafim A  Lopes B  Company R  Ferreira AM  Bebianno MJ 《Marine pollution bulletin》2008,57(6-12):529-537

Aliphatic hydrocarbons and PAHs in the whole soft tissues of Bathymodiolus azoricus from three Mid-Atlantic Ridge hydrothermal vents (Menez-Gwen, Lucky Strike and Rainbow), and Mytilus galloprovincialis from three contaminated coastal sites in South Portugal were analysed, and its effects on the digestive gland microsomes mixed-function oxygenase system (MFO) were assessed. Aliphatic hydrocarbons levels were present in the same magnitude in both coastal and hydrothermal environments, while the UCM (unresolved complex mixture) for coastal mussels were higher than in vent mussels. In general, significantly higher PAHs concentrations were found in coastal mussels, compared to B. azoricus where low molecular weight PAHs (2-3 rings) represented the majority of PAHs contrarily to what was observed in M. galloprovincialis. The MFO components were present in both mussel species, and were detected in vent mussels for the first time. However this system seems to have different roles in species from these contrasting environments. In coastal mussels MFO responded to hydrocarbon contamination while response in hydrothermal organisms appeared to be related mainly to endogenous factors.  相似文献   

Does heavy oil pollution induce bacterial diseases in Japanese flounder Paralichthys olivaceus?     

Song JY  Nakayama K  Murakami Y  Jung SJ  Oh MJ  Matsuoka S  Kawakami H  Kitamura S 《Marine pollution bulletin》2008,57(6-12):889-894

As basic research for the effect of heavy oil on the fish immune system, in this study, the number of leukocyte was counted in Japanese flounder Paralichthys olivaceus, after exposure to heavy oil at a concentration of 30 g/8L for 3 days. To compare the numbers of bacteria in the skin mucus between oil-exposed and control fish, viable bacteria were enumerated by counting colony forming unit (CFU). Compared with 5.79+/-1.88 x 10(7)leukocytes/mL in the controls, the exposed fish demonstrated higher counts, averaging 1.45+/-0.45 x 10(8)cells/mL. The bacterial numbers of control fish were 4.27+/-3.68 x 10(4)CFU/g, whereas they were 4.58+/-1.63 x 10(5)CFU/g in the exposed fish. The results suggest that immune suppression of the fish occurred due to heavy oil stressor, and bacteria could invade in the mucus, resulting in the increasing leukocyte number to prevent infectious disease.  相似文献   

Long-term reactive solute transport in an aquitard using a centrifuge model     

Timms WA  Hendry MJ 《Ground water》2008,46(4):616-628

Characterizing and predicting reactive solute transport in low hydraulic conductivity ( K ) clay-rich media is challenging because the very long transport time for solutes renders conventional column tests impractical. In this study, a centrifugation technique was developed to assess the transport of a simple aqueous solution (NaCl) by accelerating flow by centrifugal force through low K (1.1 × 10⁻¹¹ m/s) core samples. Duplicate cores (52-mm length × 33-mm diameter) were centrifuged at 330 × g for 90 d to model the migration of saline pore water (0.5 M NaCl) under in situ conditions through an approximately 17-m-thick clay prototype over approximately 24,000 years. A PHREEQC one-dimensional reactive solute transport code simulated effluent breakthrough of the NaCl during centrifugation, with best-fit cation exchange coefficients similar to batch tests. The calibrated code was used to predict solute profile development over the long term in the prototype or simulated field-scale conditions. Chromatographic separation of solutes due to ion exchange was evident over several meters in the simulated prototype and the field profile. The applicability of centrifugation methods to predict transport of more complex suites of reactive solutes over the long term is yet to be verified.  相似文献   

越南中新世滨海炭酸盐岩隆     

Maya.  MJ 陈泓君 《海洋地质》1999,(3):69-72

越南滨海碳酸盐岩多种多样,其中,受巨大的断层控制并因抬升而遭受广泛淋滤作用的大岩隆可以形成最好的储层。多数具有等储集性能的储发育于分布范围很广的台地相和断层下盘顶部的小岩隆中。本文讨论各种不同类型碳酸盐岩的岩层,岩相,成岩作用和储层性质。  相似文献   

Spatial variation of metal bioaccumulation in the hydrothermal vent mussel Bathymodiolus azoricus   总被引：1，自引：0，他引：1  

Cosson RP  Thiébaut E  Company R  Castrec-Rouelle M  Colaço A  Martins I  Sarradin PM  Bebianno MJ 《Marine environmental research》2008,65(5):405-415

The variability of the bioaccumulation of metals (Ag, Cd, Cu, Fe, Mn and Zn) was extensively studied in the mussel Bathymodiolus azoricus from five hydrothermal vent sites inside three main vent fields of increasing depth along the Mid-Atlantic Ridge: Menez Gwen, Lucky Strike and Rainbow. Metal bioaccumulation varied greatly between vent fields and even between sites inside a vent field with B. azoricus showing a great capacity to accumulate metals. The bioaccumulation of these metals also varied significantly among tissues. The main target was the gills where metals were mainly associated with soluble compounds whereas in the digestive gland they were mainly associated with insoluble compounds. Storage of metals under insoluble forms in B. azoricus seems to be a major pathway for the detoxification of both essential and non-essential metals. Mussels from the studied fields can be discriminated following their metallic load but the segregation relies partially on the composition of the metal-enriched fluids.  相似文献