Does the Phaeocystis bloom affect the diel migration of the suprabenthos community?     

Dauvin JC  Desroy N  Denis L  Ruellet T 《Marine pollution bulletin》2008,56(1):77-87

The suprabenthos comprises all bottom-dependent animals, mainly crustaceans (including decapods and peracarids), which perform--with varying amplitude, intensity and regularity--seasonal or daily vertical migrations above the sea floor. The presence of organisms in the Benthic Boundary Layer is determined by two general factors: (1) organism behaviour, which depends on the light penetration in the water column and (2) boundary-layer hydrodynamics. In the coastal zone of the eastern English Channel, during the spring Phaeocystis bloom, the presence of gelatinous colonies modifies the penetration of light in the water column, which may seriously affect the abundance and/or the behaviour of the suprabenthos community. To clarify this point, 19 suprabenthic hauls were taken with a modified Macer-GIROQ sledge both during the day and during the night, from March to June 2002 (i.e., before, during and after the bloom). Two sites, located in the coastal and offshore areas of the Ophelia medium sand macrobenthic community were investigated. The bloom had no effect on species richness and abundance in either site. However, the diel migrations of some dominant species--such as the cumaceans Pseudocuma longicornis and Pseudocuma similis, the mysid Gastrosaccus spinifer and the amphipod Stenothoe marina--were modified. During the bloom, diurnal and nocturnal suprabenthic abundances were similar, and in the absence of bloom, species remained benthic during the day. The permanent presence of suprabenthic species in the Benthic Boundary Layer could have a consequence on their predation by fish (mainly juveniles which preferentially consume small crustaceans in their diet), unless fish behaviour and predation efficiency--especially for visual predators--are also disturbed by changes in light intensity.  相似文献   

Effects of heavy metal contamination on the macrobenthic fauna in estuaries: the case of the Seine estuary   总被引：2，自引：0，他引：2  

Dauvin JC 《Marine pollution bulletin》2008,57(1-5):160-169

Heavy metal contamination levels are generally higher in estuaries than in the open sea. Some estuaries, the Seine estuary for example, have particularly high pollution levels of metals, yet continue to support a very high benthic biomass and remain quite productive. Measurements of sediment contamination are highly variable due to diverse chemical analysis methods, sediments origin and sources of contaminants found in the estuaries. Salinity appears to be the principal factor controlling contaminant distribution in the sediment and the overlying and/or interstitial waters; it also affects the bioavailability of contaminants in estuarine sediments. Of course, the response to contaminants varies greatly among species and assemblages. Trace metals explain only a small part of the variation in benthic community structure. Some species, such as the shrimp Crangon crangon, appears vulnerable to metal pollution, while other species, such as Scrobicularia plana, are able to tolerate quite high levels of cadmium in their tissue. This paper demonstrates the wide variability of benthic responses to contamination, which is probably due to the high spatio-temporal heterogeneity of the estuary. To reduce the problems due the heterogeneity and variability observed to date in the available results, it will be necessary to encourage integrated estuarine studies, in which sedimentologists, chemists, and biologists work together on the same campaigns at the same sites.  相似文献   

The Bronze Age occupation of the Black Sea coast of Georgia—New insights from settlement mounds of the Colchian plain     

Hannes Laermanns  Mikheil Elashvili  Giorgi Kirkitadze  Christopher P. Loveluck  Simon Matthias May  Daniel Kelterbaum  Revaz Papuashvili  Helmut Brückner 《Geoarchaeology》2024,39(3):335-350

Along the lower course of the Rioni and several minor rivers, more than 70 settlement mounds (local name: Dikhagudzuba) have been identified by field surveys and remote sensing techniques. They give evidence of a formerly densely populated landscape in the coastal lowlands on the Colchian plain (western Georgia) and have been dated to the Bronze Age. As yet, limited information is available on their internal architecture, the chronology of the different layers and their palaeoenvironmental context. Based on archaeological sources, remote sensing measurements of three mounds and sediment cores from one mound and its closer surroundings, our study presents a review of the relevant literature and reveals the internal structure, distribution and spatial extent of the mounds. Geochemical and sedimentological analyses of element contents (X-ray fluorescence) and granulometry helped to identify different stratigraphical layers and differentiate between natural facies and anthropogenic deposits; using the Structure-from-Motion technique the mounds' dimensions were calculated. The studied settlement mounds had relatively small dimension (varying from 30 to 100 m in diameter) and were similar in their stratigraphy. Measurement of elements that can identify types of human activity, notably metals and phosphorus, suggest changing intensities of human occupation, pastoral agriculture and metalworking through the occupation sequence. According to the ¹⁴C chronology, the formation of the settlements occurred during the first half of the second millennium B.C., which confirms the archaeological interpretation of their Bronze Age origin. The narrow age difference between the lowermost and uppermost anthropogenic layers indicates an intentional construction of the mounds, rather than a successive accumulation of construction debris due to the disintegration of loam bricks by weathering. Therefore, they are indeed mounds and not tells. It is most likely that the characteristic circular moats that surround them were the source of their construction material. Fluvial and alluvial processes in a warm and humid climate dominated the environment of the mounds.  相似文献   

Simultaneous horst-basin formation and magmatism during Late Variscan transtension: evidence from 40Ar/39Ar and 207Pb/206Pb geochronology in the Ruhla Crystalline Complex     

A. Zeh  M. A. Cosca  H. Brätz  M. Okrusch  M. Tichomirowa 《International Journal of Earth Sciences》2000,89(1):52-71

40 Ar/³⁹Ar–mica and ²⁰⁷Pb/²⁰⁶Pb–zircon dates are presented and combined with existing P–T data and the sedimentary record. These data indicate that the RCC was faulted into three segments which underwent different exhumation histories during the Late Carboniferous/Early Permian. The eastern segment shows ⁴⁰Ar/³⁹Ar–biotite data of336 ±4 and 323±3 Ma. Furthermore, it is intruded by the Thuringian Hauptgranite dated at 337±4 Ma by the ²⁰⁷Pb/²⁰⁶Pb single zircon method. At approximately 300 Ma rocks of the eastern segment were finally exposed and, subsequently, subsided as part of the Oberhof pull-apart basin, filled by Late Carboniferous/Early Permian molasse sediments and volcanic rocks (296–285 Ma; Goll 1996). A similar Late Carboniferous evolution is inferred for the western segment, since it is also overlain by Upper Carboniferous volcanic rocks. In contrast to the eastern and western segments, distinctly younger intrusion and cooling ages were recorded for the central segment of the RCC (⁴⁰Ar/³⁹Ar muscovite: 311±3 Ma; ⁴⁰Ar/³⁹Ar biotite: 293–288±3 Ma) that was intruded by the Trusetal Granite, the Ruhla Granite and Brotterode Diorite (²⁰⁷Pb/²⁰⁶Pb single zircon: 298±2, 295±3, 289±4 Ma, respectively). These young data are unique in the MGCR and testify that plutonic activity and cooling of basement rocks took place simultaneously with basin formation and volcanism in the eastern and western segments. Overlying Upper Permian (Zechstein) and Triassic sediments indicate final exposure of the central segment by approximately 260 Ma, as a part of the Ruhla-Schleusingen Horst. Combination of these results with P–T data from the contact aureole of the Trusetal granite indicate that the central segment was unroofed by at least 8.5 km during the Late Carboniferous. The Late Carboniferous/Early Permian horst-basin formation, documented in the RCC, is due to dextral transtensional movements along the NW-trending Franconian fault system. It may have been enhanced by mantle upwelling widespread in Central Europe during the Early Permian that also caused intensive magmatism in the Thuringian Forest region. Received: 2 February 1999 / Accepted: 15 November 1999  相似文献   

An Overview of Geodetic Volcano Research in the Canary Islands     

José Fernández  Pablo J. González  Antonio G. Camacho  Juan F. Prieto  Guadalupe Brú 《Pure and Applied Geophysics》2015,172(11):3189-3228

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Linking social capacities and risk communication in Europe: a gap between theory and practice?     

Corina H?ppner  Rebecca Whittle  Michael Bründl  Matthias Buchecker 《Natural Hazards》2012,64(2):1753-1778

Although both improved risk communication and the building of social capacities have been advocated as vital ways to increase societies?? resilience towards natural hazards across the world, the literature has rarely examined the ways in which these two concepts may integrate in theory and practice. This paper is an attempt to address this gap in a European context. It begins with a conceptual discussion that unites the literature on risk communication with the literature on social capacity building. We then use the insights from this discussion as a basis to conduct a review of 60 risk communication practices from across Europe. This review indicates a gap between theory and practice because, whilst the literature highlights the importance of integrated and coordinated communication campaigns featuring both a one-way transfer and a two-way dialogue between the public, stakeholders and decision-makers, the majority of the communication practices reviewed here appear to be relatively disparate initiatives that rely on one-way forms of communication. On the basis of these findings, we conclude by making some recommendations for the way in which such practices could be improved in order to be more supportive of social capacities across Europe.  相似文献   

An efficient stochastic approach for building footprint extraction from digital elevation models     

O. Tournaire  M. Brédif  D. Boldo  M. Durupt 《ISPRS Journal of Photogrammetry and Remote Sensing》2010,65(4):317-327

In the past two decades, building detection and reconstruction from remotely sensed data has been an active research topic in the photogrammetric and remote sensing communities. Recently, effective high level approaches have been developed, i.e., the ones involving the minimization of an energetic formulation. Yet, their efficiency has to be balanced by the amount of processing power required to obtain good results.In this paper, we introduce an original energetic model for building footprint extraction from high resolution digital elevation models (≤1 m) in urban areas. Our goal is to formulate the energy in an efficient way, easy to parametrize and fast to compute, in order to get an effective process still providing good results.Our work is based on stochastic geometry, and in particular on marked point processes of rectangles. We therefore try to obtain a reliable object configuration described by a collection of rectangular building footprints. To do so, an energy function made up of two terms is defined: the first term measures the adequacy of the objects with respect to the data and the second one has the ability to favour or penalize some footprint configurations based on prior knowledge (alignment, overlapping, …). To minimize the global energy, we use a Reversible Jump Monte Carlo Markov Chain (RJMCMC) sampler coupled with a simulated annealing algorithm, leading to an optimal configuration of objects. Various results from different areas and resolutions are presented and evaluated. Our work is also compared with an already existing methodology based on the same mathematical framework that uses a much more complex energy function. We show how we obtain similarly good results with a high computational efficiency (between 50 and 100 times faster) using a simplified energy that requires a single data-independent parameter, compared to more than 20 inter-related and hard-to-tune parameters.  相似文献   

Semantic Enablement for Spatial Data Infrastructures   总被引：4，自引：0，他引：4  

Krzysztof Janowicz  Sven Schade  Arne Bröring  Carsten Keßler  Patrick Maué  Christoph Stasch 《Transactions in GIS》2010,14(2):111-129

Building on abstract reference models, the Open Geospatial Consortium (OGC) has established standards for storing, discovering, and processing geographical information. These standards act as a basis for the implementation of specific services and Spatial Data Infrastructures (SDI). Research on geo‐semantics plays an increasing role to support complex queries and retrieval across heterogeneous information sources, as well as for service orchestration, semantic translation, and on‐the‐fly integration. So far, this research targets individual solutions or focuses on the Semantic Web, leaving the integration into SDI aside. What is missing is a shared and transparent Semantic Enablement Layer for SDI which also integrates reasoning services known from the Semantic Web. Instead of developing new semantically enabled services from scratch, we propose to create profiles of existing services that implement a transparent mapping between the OGC and the Semantic Web world. Finally, we point out how to combine SDI with linked data.  相似文献   

High resolution characterization of northwest Mediterranean coastal waters thermal regimes: To better understand responses of benthic communities to climate change     

Nathaniel Bensoussan  Jean-Claude Romano  Jean-Georges Harmelin  Joaquim Garrabou 《Estuarine, Coastal and Shelf Science》2010

In the North West Mediterranean (NWM), mass mortality events (MME) of long-lived benthic species that have occurred over the last two decades have been related to regional warming trend. Gaining robust data sets on thermal regimes is critical to assess conditions to which species have adapted, detect extreme events and critically evaluate biological impacts. High resolution temperature (T) time series obtained during 1999–2006 from 5 to 40 m depth at four contrasted sites of the NWM were analyzed: Area Marina Protegida de les Illes Medes (NE Spain), Riou (Marseilles, France), Parc National de Port-Cros (France), and Réserve Naturelle de Scandola (Corsica, France). The seasonal pattern showed winter T around 11–13 °C, and summer T mainly around 22–24 °C near surface to 18–20 °C at depth. Stratification dynamics showed recurrent downwellings (>40 m) at Medes, frequent observation (1/3rd of the summer) of deep and cold upwelled waters at Riou, while Scandola exhibited stable summer stratification and highest suprathermoclinal T. Port-Cros showed an intermediate regime that oscillated between Riou and Scandola depending on the occurrence of northern winds. Data distribution study permitted to identify and to characterize 3 large scale positive anomalies concomitant with the mass mortality outbreaks of summers 1999, 2003 and 2006. The analysis of biological surveys on gorgonian populations showed significant impacts during the 3 years with temperature anomalies. Besides the degree of impact showed inter-annual differences which could be related to different T conditions concomitant to mortality events, from slight increase in T extreme of only 1–2 °C over short duration, to lengthened more classical summer conditions. Our results therefore support the hypothesis that shallow NWM populations of long-lived benthic species are living near their upper thermal thresholds. Given actual trends and projections in NWM, the repetition of new MMEs in the next decades is extremely likely. In such context, the acquisition of dedicated high resolution T series proves to be crucial for increasing our detection, understanding and forecasting abilities.  相似文献   

Spatial autocorrelation and data uncertainty in the American Community Survey: a critique     

Paul H. Jung  Jean-Claude Thill  Michele Issel 《International journal of geographical information science》2019,33(6):1155-1175

ABSTRACT

We argue that the use of American Community Survey (ACS) data in spatial autocorrelation statistics without considering error margins is critically problematic. Public health and geographical research has been slow to recognize high data uncertainty of ACS estimates, even though ACS data are widely accepted data sources in neighborhood health studies and health policies. Detecting spatial autocorrelation patterns of health indicators on ACS data can be distorted to the point that scholars may have difficulty in perceiving the true pattern. We examine the statistical properties of spatial autocorrelation statistics of areal incidence rates based on ACS data. In a case study of teen birth rates in Mecklenburg County, North Carolina, in 2010, Global and Local Moran’s I statistics estimated on 5-year ACS estimates (2006–2010) are compared to ground truth rate estimates on actual counts of births certificate records and decennial-census data (2010). Detected spatial autocorrelation patterns are found to be significantly different between the two data sources so that actual spatial structures are misrepresented. We warn of the possibility of misjudgment of the reality and of policy failure and argue for new spatially explicit methods that mitigate the biasedness of statistical estimations imposed by the uncertainty of ACS data.  相似文献