Acute Disturbance of Lake Pontchartrain Benthic Communities by Hurricane Katrina     

Michael A. Poirrier  Zoe Rodriguez del Rey  Elizabeth A. Spalding 《Estuaries and Coasts》2008,31(6):1221-1228

In 2005, Hurricane Katrina produced a distinct, acute ecological disturbance of the benthic invertebrate community of Lake Pontchartrain, LA, USA. The bivalve Rangia cuneata and other community dominants were lost from 50% (815 km²) of the lake bottom. The storm surge directly killed benthic organisms and produced salinity stratification that caused episodes of detrimental low dissolved oxygen concentration at depths >3.7 m. Past disturbance of the bottom by shell dredging and intrusion of higher salinity bottom water through deep shipping channels appears to have contributed to the severity of this impact. Colonization by tolerant opportunistic taxa occurred, but low rainfall after Katrina has slowed the recovery of the typical rangia community. A decrease in water transparency and an increase in turbidity and chlorophyll a were associated with the loss of clam biomass. Other hurricanes may have produced less obvious but similar effects on smaller spatial and temporal scales.  相似文献   

Further evidence for magnetic susceptibility as a proxy for the evaluation of heavy metals in mining wastes: case study of Tlalpujahua and El Oro Mining Districts     

Juan Morales  María del Sol Hernández-Bernal  Pedro Corona-Chávez  Avto Gogichaishvili  Francisco Bautista 《Environmental Earth Sciences》2016,75(4):309

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Progress and Challenges in Coupled Hydrodynamic-Ecological Estuarine Modeling     

Neil K. Ganju  Mark J. Brush  Brenda Rashleigh  Alfredo L. Aretxabaleta  Pilar del Barrio  Jason S. Grear  Lora A. Harris  Samuel J. Lake  Grant McCardell  James O’Donnell  David K. Ralston  Richard P. Signell  Jeremy M. Testa  Jamie M. P. Vaudrey 《Estuaries and Coasts》2016,39(2):311-332

Numerical modeling has emerged over the last several decades as a widely accepted tool for investigations in environmental sciences. In estuarine research, hydrodynamic and ecological models have moved along parallel tracks with regard to complexity, refinement, computational power, and incorporation of uncertainty. Coupled hydrodynamic-ecological models have been used to assess ecosystem processes and interactions, simulate future scenarios, and evaluate remedial actions in response to eutrophication, habitat loss, and freshwater diversion. The need to couple hydrodynamic and ecological models to address research and management questions is clear because dynamic feedbacks between biotic and physical processes are critical interactions within ecosystems. In this review, we present historical and modern perspectives on estuarine hydrodynamic and ecological modeling, consider model limitations, and address aspects of model linkage, skill assessment, and complexity. We discuss the balance between spatial and temporal resolution and present examples using different spatiotemporal scales. Finally, we recommend future lines of inquiry, approaches to balance complexity and uncertainty, and model transparency and utility. It is idealistic to think we can pursue a “theory of everything” for estuarine models, but recent advances suggest that models for both scientific investigations and management applications will continue to improve in terms of realism, precision, and accuracy.  相似文献   

The rise of the diptera‐microbial mat interactions during the Cenozoic: consequences for the sedimentary record of saline lakes     

M. Esther Sanz‐Montero  José‐Pedro Calvo  M. Angeles García del Cura  Concepción Ornosa  Raimundo Outerelo  J. Pablo Rodríguez‐Aranda 《地学学报》2013,25(6):465-471

Shoreline gypsiferous sediments of an inland lake in central Spain furnishes valuable insight into reconstructions of early sedimentary changes related to shore fly–microbial mat interactions in fossil gypsum precipitating saline lake systems. The association of adult and larval forms of Ephydra (Diptera) with microbial matgrounds overlying the lake margin results in the formation of gypsiferous meniscate back‐filled burrows that provide an analogue for recurring, extensively developed trace fossils that occur in Cenozoic, but not older, lacustrine gypsum rocks. In this setting, sediment burrowing by ephydridae hinders significant preservation of microbialites. The overwhelming rise of Diptera at the onset of the Cenozoic resulted in extensive feeding and dwelling activity and contributed to reshape the saline aquatic habitat where microbial mats thrived, thus leading to the formation of specific trace fossils that are illustrative of the existence of microbes in the paleoenvironment.  相似文献   

Dissolved DMSO production via biological and photochemical oxidation of dissolved DMS in the Ross Sea,Antarctica     

Daniela A. del Valle  David J. Kieber  Dierdre A. Toole  John Bisgrove  Ronald P. Kiene 《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(2):166-177

Dimethylsulfoxide (DMSO) is an important degradation product of the climate-influencing gas dimethylsulfide (DMS). In the Ross Sea, Antarctica, dissolved DMSO (DMSOd) concentrations exhibited substantial seasonal and vertical variations. Surface water DMSOd concentrations in pre-bloom waters were very low (<1 nM) but increased rapidly up to 41 nM during the spring Phaeocystis antarctica bloom (late November). Increases in DMSOd concentrations lagged by several days increases in DMS concentrations. Although DMSOd concentrations reached relatively high levels during the spring bloom, concentrations were generally higher (36.3–60.6 nM) during summer (January), even though phytoplankton biomass and DMS concentrations had decreased by that time. During both seasons, DMSOd concentrations were substantially higher within the surface mixed layer than below it. DMSOd production from biological DMS consumption (BDMSC) was higher during late November (3.4–5.2 nM d^?1) than during the summer (0.7–2.4 nM d^?1); therefore, production via BDMSC alone could not explain the higher DMSOd concentrations encountered during the summer. Mixed layer-integrated DMSOd production from BDMSC was 2.5–13.7 times greater than production from dissolved DMS photolysis during the P. antarctica bloom, while photolysis contributed 1.3 times more DMSO than BDMSC before the bloom. The DMSO yield from BDMSC was consistently higher within the upper mixed layer than at depths below. Experimental incubations with water from the mixed layer showed that exposure to full spectrum sunlight for 72 h caused an increase in the DMSO yield whereas exposure to only photosynthetically active radiation did not. This suggests that ultraviolet radiation is a potential factor shifting the fate of biologically consumed DMS toward DMSO. In general, the highest DMSO yields from BDMSC were in samples with slow biological DMS turnover, whereas fast turnover favored sulfate rather than DMSO as a major end-product. This study provides the first detailed information about DMSOd distribution and production in the Ross Sea and points to DMSOd as an important biological and photochemical degradation product of DMS and a major reservoir of methylated sulfur in these polar surface waters.  相似文献   

Oceanographic conditions in North and Northwest Iberia and their influence on the Prestige oil spill     

Ruiz-Villarreal M  González-Pola C  Diaz del Rio G  Lavin A  Otero P  Piedracoba S  Cabanas JM 《Marine pollution bulletin》2006,53(5-7):220-238

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ENSO signals in South America: rains and floods in the Paraná River region during colonial times   总被引：1，自引：0，他引：1  

María del Rosario Prieto 《Climatic change》2007,83(1-2):39-54

Several studies show that the El Niño-Southern Oscillation (ENSO) is an important factor in determining interannual rainfall variability in South America. This signal is detected in the region including Northeastern Argentina, Uruguay and part of southern Brazil, in the form of excessive rains and big floods in the regional rivers. To check that this relationship was similar in the past the objectives of this paper were to construct a time series of large floods in the Paraná River region from documentary records, during the sixteenth to eighteenth centuries, and to evaluate the relationship between that historical record of extreme floods, the ENSO documentary evidence (Ortlieb, The Documented Historical Record of El Niño Events in Perú: An Update of the Quinn Record (Ortlieb, sixteenth through nineteenth centuries, Diaz and Markgraf, (eds.), El Niño and the southern oscillation. Multiscale variability and global and regional Impacts. Cambridge University Press, pp. 207–295, 2001; Quinn and Neal, The historical record of El Niño events, Bradley and Jones (eds.), Climate since a.d. 1500, Routledges, pp. 623–648, 1992) and the temperature index of the Pacific Ocean (Mann ME et al., Global temperature patterns in past centuries: an interactive presentation, IGBP pages/world data center for paleoclimatology data contribution series #2000-075. NOAA/NGDC Paleoclimatology Program, Boulder CO, USA, 2000). Considering that the period 1904–2000, where 11 out of 16 floods occurred during El Niño events, it can be concluded that the proportion of years with exceptional flow volume in the Paraná River in years with El Niño events in the seventeenth and eighteenth centuries was relatively lower than that of the twentieth century. The reason for this difference is discussed.  相似文献   

Exoplanet status report: Observation, characterization and evolution of exoplanets and their host stars     

H. Lammer  A. Hanslmeier  J. Schneider  I. K. Stateva  M. Barthelemy  A. Belu  D. Bisikalo  M. Bonavita  V. Eybl  V. Coudé du Foresto  M. Fridlund  R. Dvorak  S. Eggl  J. -M. Grießmeier  M. Güdel  E. Günther  W. Hausleitner  M. Holmström  E. Kallio  M. L. Khodachenko  A. A. Konovalenko  S. Krauss  L. V. Ksanfomality  Yu. N. Kulikov  K. Kyslyakova  M. Leitzinger  R. Liseau  E. Lohinger  P. Odert  E. Palle  A. Reiners  I. Ribas  H. O. Rucker  N. Sarda  J. Seckbach  V. I. Shematovich  A. Sozzetti  A. Tavrov  M. Xiang-Grüß 《Solar System Research》2010,44(4):290-310

After the discovery of more than 400 planets beyond our Solar System, the characterization of exoplanets as well as their host stars can be considered as one of the fastest growing fields in space science during the past decade. The characterization of exoplanets can only be carried out in a well coordinated interdisciplinary way which connects planetary science, solar/stellar physics and astrophysics. We present a status report on the characterization of exoplanets and their host stars by reviewing the relevant space- and ground-based projects. One finds that the previous strategy changed from space mission concepts which were designed to search, find and characterize Earth-like rocky exoplanets to: A statistical study of planetary objects in order to get information about their abundance, an identification of potential target and finally its analysis. Spectral analysis of exoplanets is mandatory, particularly to identify bio-signatures on Earth-like planets. Direct characterization of exoplanets should be done by spectroscopy, both in the visible and in the infrared spectral range. The way leading to the direct detection and characterization of exoplanets is then paved by several questions, either concerning the pre-required science or the associated observational strategy.  相似文献   

Modeling the Acid–Base Surface Properties of Aquatic Sediments     

L. Borgnino  M. G. Garcia  M. V. del Hidalgo  M. Avena  C. P. De Pauli  M. A. Blesa  P. J. Depetris 《Aquatic Geochemistry》2010,16(2):279-291

We propose a model that explains the acid–base surface properties of clastic sediments from two Argentinean reservoir lakes. The model uses potentiometric titration data sets and fixed parameters such as the apparent stability constants and reaction stoichiometries of acid–base equilibriums involving known mineral phases. The model considers that sediments act as a set of independent sorption surfaces, such as organic matter, clay silicate, and iron (hydr)oxides, thus the acid–base equilibrium and the correspondent protolytic constants are represented by a humic acid, a Na-illite, and a poor crystalline Fe-hydr(oxide). In agreement with experimental data, the model predicts that all sediment samples show a similar charging behavior, increasing the negative charge as the pH increases. The net charge of sediments is controlled by the presence of negatively charged minerals and/or organic matter coatings. This reveals the great influence of clays and organic matter functional groups on the acid–base surface properties of sediments, and consequently on the surface reactivity toward contaminant transport.  相似文献   

Extinction techniques and impact on dust property determination     

D. Froebrich  C. del Burgo 《Monthly notices of the Royal Astronomical Society》2006,369(4):1901-1910

The near-infrared (NIR) extinction power-law index (β) and its uncertainty is derived from three different techniques based on star counts, colour excess and a combination of them. We have applied these methods to Two Micron All Sky Survey (2MASS) data to determine maps of β and NIR extinction of the small cloud IC 1396 W. The combination of star counts and colour excess results in the most reliable method to determine β. It is found that the use of the correct β map to transform colour excess values into extinction is fundamental for column density profile analysis of clouds. We describe how artificial photometric data, based on the model of stellar population synthesis of the Galaxy, can be used to estimate uncertainties and derive systematic effects of the extinction methods presented here. We find that all colour excess based extinction determination methods are subject to small but systematic offsets, which do not affect the star counting technique. These offsets occur since stars seen through a cloud do not represent the same population as stars in an extinction-free control field.  相似文献