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81.
Marianne Holmer Núria Marbà Morgane Lamote Carlos M. Duarte 《Estuaries and Coasts》2009,32(3):456-466
Species of the macroalgae Caulerpa sp. are increasingly being observed in meadows of the endemic Mediterranean seagrass Posidonia oceanica, and in particular Caulerpa taxifolia, has been considered as an invasive species leading to seagrass decline. Studies have so far failed to reveal the underlying
mechanisms of the success of the macroalgae, and here, we examine how biogeochemical changes of the environment associated
to indigenous (Caulerpa prolifera) and non-indigenous (Caulerpa racemosa and C. taxifolia) species affect the habitat of P. oceanica. Two of the species (C. prolifera and C. racemosa) affect the sediment biogeochemical conditions by increasing organic matter pools, microbial activity, and sulfide pools
of the sediments, and limited effects were found for C. taxifolia. Biomass of the macroalgae contributed to the extent of impacts, and high sulfide invasion into the seagrasses and regression
of the meadow were pronounced at the location with the highest Caulerpa biomass. This suggests that Caulerpa invasion contributes to seagrass decline probably because Caulerpa thrives better than the seagrasses in the modified environment. 相似文献
82.
Joan Masó Xavier Pons Alaitz Zabala 《International journal of geographical information science》2013,27(6):983-1014
Spatial data infrastructure (SDI) actors have great expectations for the second-generation SDI currently under development. However, SDIs have many implementation problems at different levels that are delaying the development of the SDI framework. The aims of this article are to identify these difficulties, in the literature and based on our own experience, in order to determine how mature and useful the current SDI phenomena are. We can then determine whether a general reconceptualization is necessary or rather a set of technical improvements and good practices needs to be developed before the second-generation SDI is completed. This study is based on the following aspects: metadata about data and services, data models, data download, data and processing services, data portrayal and symbolization, and mass market aspects. This work aims to find an equilibrium between user-focused geoportals and web service interconnection (the user side vs. the server side). These deep reflections are motivated by a use case in the healthcare area in which we employed the Catalan regional SDI. The use case shows that even one of the best regional SDI implementations can fail to provide the required information and processes even when the required data exist. Several previous studies recognize the value of applying Web 2.0 and user participation approaches but few of these studies provide a real implementation. Another objective of this work is to show that it is easy to complement the classical, international standard-based SDI with a participative Web 2.0 approach. To do so, we present a mash-up portal built on top of the Catalan SDI catalogues. 相似文献
83.
AbstractThe Hilhorst model was used to convert bulk electrical conductivity (σb) to pore water electrical conductivity (σp) under laboratory conditions by using the linear relationship between the soil dielectric constant (εb) and σb. In the present study, applying the linear relationship εb–σb to data obtained from field capacitance sensors resulted in strong positive autocorrelations between the residuals of that regression. We were able to derive an accurate offset of the relationship εb–σb and to estimate the evolution of σp over time by including a stochastic component to the linear model, rearranging it to a time-varying dynamic linear model (DLM), and using Kalman filtering and smoothing. The offset proved to vary for each depth in the same soil profile. A reason for this might be the changes in soil temperature along the soil profile.
Editor D. Koutsoyiannis; Associate editor M.D. Fidelibus 相似文献
84.
Magma plumbing beneath Anak Krakatau volcano, Indonesia: evidence for multiple magma storage regions
B?rje Dahren Valentin R. Troll Ulf B. Andersson Jane P. Chadwick Màiri F. Gardner Kairly Jaxybulatov Ivan Koulakov 《Contributions to Mineralogy and Petrology》2012,163(4):631-651
Understanding magma plumbing is essential for predicting the behaviour of explosive volcanoes. We investigate magma plumbing
at the highly active Anak Krakatau volcano (Indonesia), situated on the rim of the 1883 Krakatau caldera by employing a suite
of thermobarometric models. These include clinopyroxene-melt thermobarometry, plagioclase-melt thermobarometry, clinopyroxene
composition barometry and olivine-melt thermometry. Petrological studies have previously identified shallow magma storage
in the region of 2–8 km beneath Krakatau, while existing seismic evidence points towards mid- to deep-crustal storage zone(s),
at 9 and 22 km, respectively. Our results show that clinopyroxene in Anak Krakatau lavas crystallized at a depth of 7–12 km,
while plagioclase records both shallow crustal (3–7 km) and sub-Moho (23–28 km) levels of crystallization. These magma storage
regions coincide with well-constrained major lithological boundaries in the crust, implying that magma ascent and storage
at Anak Krakatau is strongly controlled by crustal properties. A tandem seismic tomography survey independently identified
a separate upper crustal (<7 km) and a lower to mid-crustal magma storage region (>7 km). Both petrological and seismic methods
are sensitive in detecting magma bodies in the crust, but suffer from various limitations. Combined geophysical and petrological
surveys, in turn, offer increased potential for a comprehensive characterization of magma plumbing at active volcanic complexes. 相似文献
85.
Raquel Vaquer-Sunyer Carlos M. Duarte Gabriel Jordà Sergio Ruiz-Halpern 《Estuaries and Coasts》2012,35(5):1182-1192
Hypoxia is emerging as a major threat to marine coastal biota. Predicting its occurrence and elucidating the driving factors are essential to set successful management targets to avoid its occurrence. This study aims to elucidate the effects of warming on the likelihood of hypoxia. High-frequency dissolved oxygen measurements have been used to estimate gross primary production (GPP), net ecosystem production (NEP) and community respiration (CR) in a shallow macroalgae (Caulerpa prolifera) ecosystem in a highly human-influenced closed Mediterranean bay. Daily averaged GPP and CR ranged from 0 to 1,240.9 and 51.4 to 1,297.3?mmol?O2?m?2?day?1, respectively. The higher GPP and CR were calculated for the same day, when daily averaged water temperature was 28.3?°C, and resulted in a negative NEP of ?56.4?mmol?O2?m?2?day?1. The ecosystem was net heterotrophic during the studied period, probably subsidized by allochthonous organic inputs from ground waters and from the surrounding town and boating activity. Oxygen dynamics and metabolic rates strongly depend on water temperature, with lower oxygen content at higher temperatures. The probability of hypoxic conditions increased at a rate of 0.39?% °C?1 (±0.14?% °C?1). Global warming will increase the likelihood of hypoxia in the bay studied, as well as in other semi-enclosed bays. 相似文献
86.
Lidia Romero-Viana Ramon Julià Martin Schimmel Antonio Camacho Eduardo Vicente M. Rosa Miracle 《Climatic change》2011,107(3-4):343-361
We present the first winter (December to March) rainfall reconstruction based in a novel proxy, the thickness of annual calcite laminations preserved in Lake La Cruz (central–eastern Spain). A previous calibration analysis between laminae thickness and the instrumental data series (1950 to present) indicated a highly significant correlation with winter rainfall. Therefore this study attempts the winter rainfall reconstruction since the onset of laminations (1579 a.d.) by means of the calibration function previously developed. The verification analysis between inferred annual values and earlier instrumental data (1859–1949) confirms the suitability of this novel proxy and the reliability of the series reconstructed. The reconstructed series show the fluctuating character of winter rainfall in the western Mediterranean area; interdecadal dry periods alternated with wetter periods following, in a board sense, the pattern recorded by documentary sources in other regions of the Iberian Peninsula. At present times regional winter rainfall anomalies are highly correlated with the phase of the North Atlantic Oscillation (NAO). However the time series analysis showed the dominance of nonstationary components at high frequencies of the climate signal over the last four centuries suggesting that the connection between winter rainfall and the NAO has not been stable over time and also other modes of variability, not only NAO, may have conditioned winter rainfall variability. 相似文献
87.
Bouchra Nechad Aida Alvera-Azcaràte Kevin Ruddick Naomi Greenwood 《Ocean Dynamics》2011,61(8):1205-1214
In situ measurements of total suspended matter (TSM) over the period 2003–2006, collected with two autonomous platforms from
the Centre for Environment, Fisheries and Aquatic Sciences (Cefas) measuring the optical backscatter (OBS) in the southern
North Sea, are used to assess the accuracy of TSM time series extracted from satellite data. Since there are gaps in the remote
sensing (RS) data, due mainly to cloud cover, the Data Interpolating Empirical Orthogonal Functions (DINEOF) is used to fill
in the TSM time series and build a continuous daily “recoloured” dataset. The RS datasets consist of TSM maps derived from
MODIS imagery using the bio-optical model of Nechad et al. (Rem Sens Environ 114: 854–866, 2010). In this study, the DINEOF
time series are compared to the in situ OBS measured in moderately to very turbid waters respectively in West Gabbard and
Warp Anchorage, in the southern North Sea. The discrepancies between instantaneous RS, DINEOF-filled RS data and Cefas data
are analysed in terms of TSM algorithm uncertainties, space–time variability and DINEOF reconstruction uncertainty. 相似文献
88.
Ben Ameur W Ben Hassine S Eljarrat E El Megdiche Y Trabelsi S Hammami B Barceló D Driss MR 《Marine environmental research》2011,72(5):258-264
Concentrations of ten polybrominated diphenyl ethers (PBDEs) and eight methoxylated polybrominated diphenyl ethers (MeO-PBDEs) in mullet (Mugil cephalus) and sea bass (Dicentrarchus labrax) collected from the Bizerte Lagoon and the Mediterranean Sea were investigated. To the best of our knowledge, this is the first report of these compounds in marine fishes from Tunisia. The PBDE mean concentrations in fish from Bizerte Lagoon were 45.3 and 96.2 ng g(-1) lw respectively in mullet and sea bass, while the concentrations of these compounds in mullet and sea bass from Mediterranean Sea were 7.80 and 27.9 ng g(-1) lw respectively. MeO-PBDE concentrations in mullet and sea bass from Bizerte Lagoon ranged from 6.46 to 286 ng g(-1) lw and from 49.4 to 798 ng g(-1) lw respectively, while the concentrations of these compounds in mullet and sea bass from Mediterranean Sea ranged from 190 to 401 ng g(-1) lw and from 353 to 578 ng g(-1) lw respectively. The total PBDEs and total MeO-PBDEs concentration in fish from Bizerte Lagoon were similar or slightly lower than those reported for other species from other locations around the world. 相似文献
89.
Paolo D’Adda Andrea Zanchi Maria Bergomi Fabrizio Berra Marco G. Malusà Annalisa Tunesi Stefano Zanchetta 《International Journal of Earth Sciences》2011,100(5):1095-1113
The Triassic succession of the central Southern Alps (Italy) is stacked into several units bounded by south-verging low-angle
thrust faults, which are related to two successive steps of crustal shortening. The thrust surfaces are cut by high-angle
extensional and strike-slip faults, which controlled the emplacement of hypabissal magmatic intrusions that post-date thrusts
motions. Intrusion ages based on SHRIMP U–Pb zircon dating span between 42 ± 1 and 39 ± 1 Ma, suggesting close time relationships
with the earliest Adamello intrusion stages and, more in general, with the widespread calc-alkaline magmatism described in
the Southern Alps. Fission-track ages of magmatic apatites are indistinguishable from U–Pb crystallization ages of zircons,
suggesting that the intrusion occurred in country rocks already exhumed above the partial annealing zone of apatite (depth < 2–4 km).
These data indicate that the central Southern Alps were already structured and largely exhumed in the Middle Eocene. Although
we describe minor faults affecting magmatic bodies and local reactivations of older structures, no major internal deformations
have occurred in the area after the Bartonian. Neogene deformations were instead concentrated farther south, along the frontal
part of the belt. 相似文献
90.
We determined the weather type, according to the Jenkinson and Collison procedure, of the 22 646 days in the 1948-2009 period for the western Mediterranean basin. The analysis is based upon the surface pressure values of the NCEP/NCAR reanalysis, for a grid of nine points with extreme vertices at 45º N, 5º W and 35º N, 15º E, which provides a broad synoptic catalogue for this region. We analyzed the trends of the types and their different groupings during the same period. The most frequent type is U (undetermined), with an annual average of approximately 100 days (99.4, 27.2%), followed by type A (anticyclone), with 75.5 days/ year (20.7%), and C (depression), with 67.8 days/year (18.6%). The high frequency of type U is due to the habitual pressure of baric fields with a low gradient over Mediterranean waters in the warm half of the year. According to their directions, the types from the west are the most frequent and those from the south, the least. The monthly regime of the most frequent types and groupings is quite regular; type C groups, as well as advective and cyclonic curvature groups, present summertime minima and maxima in the cold half of the year, whereas the opposite occurs with types U and A. The main statistically significant annual trends in the 1948-2009 period involve a decrease in type A (–4.19 days/decade, that is, –29.0%) and an increase in type U, the cyclonic types and those presenting an easterly component. On comparing the 31-yr sub-periods 1948-1978 and 1979-2009, the tendencies of A and U were confirmed, and increases can generally be seen in the types presenting an easterly component and a decrease in those with a westerly component. The variation in type A ranged from 2490 days in the first sub-period to 2192 in the second one (p = 0.000), mainly concentrated in summer and autumn. This evident reduction of type A coincides, paradoxically, with an increase in the sea surface pressure variable (+0.31 hPa/decade) throughout the 62 years of analysis. The negative trend found in type A differs from the results of some studies. The different analysis periods, the different scales or areas of study and the variety of methods used to determine the weather types can account for the fact that these results are discordant. Moreover, warming over the last few decades in the waters of the western Mediterranean basin, as well as the clearly cyclogenetic character of the gulfs of Lion and Genoa, might account for the decrease in type A and the increase in the cyclonic curvature types. 相似文献