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51.
Coastal areas are typically subjected to a range of stressors, but they now face the additional stressor of climate change, manifested in part by an increased intensity and frequency of extreme weather events. Thus, the Mondego estuary (Portugal) has experienced organic enrichment (eutrophication) issues and these are potentially exacerbated by extreme weather events (floods, droughts and heat waves). In this paper, we explore the impact of interactions of these different stressors on the ecology of the system, specifically on the two key components, the seagrass Zostera noltii and the mud snail Hydrobia ulvae. Extreme events affected different components of the estuarine ecosystem (primary producers and macrofauna) differently. Whilst the floods directly impacted on H. ulvae, by wiping out part of its population, they did not directly affect the biomass of Z. noltii. In contrast, drought events, through their effects on salinity, directly impacted the biomass of Zostera, which had knock-on effects on the dynamics of H. ulvae. We conclude that over the period when the estuary experienced eutrophication, extreme weather events contributed to the overall degradation of the estuary, while during the recovery phase following the introduction of a management programme, those extreme weather episodes delayed the recovery process significantly. 相似文献
52.
P.G. Cardoso D. Raffaelli A.I. Lillebø T. Verdelhos M.A. Pardal 《Estuarine, Coastal and Shelf Science》2008
Marine and coastal environments are among the most ecologically and socio-economically important habitats on Earth. However, climate change associated with a variety of anthropogenic stressors (e.g. eutrophication) may interact to produce combined impacts on biodiversity and ecosystem functioning, which in turn will have profound implications for marine ecosystems and the economic and social systems that depend upon them. 相似文献
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Pietro?Carveni Giuliana?MeleEmail author Santo?Benfatto Sebastiano?Imposa Maria?Salleo Puntillo 《Bulletin of Volcanology》2011,73(6):633-638
Unique volcanic structures, known in the literature as “lava trees” and “tree molds”, have formed at several sites on Mt.
Etna volcano (northeastern Sicily, Italy). They form when a fluid lava flow runs over a tree, wraps around it and, while the
wood burns off, solidifies forming a hollow cast of the tree. The inhabitants of the Etna area call these formations “pietre
cannone” (“cannon stones”) because of their cylindrical shape. The first documentation of lava trees is from Hawaii, but the
first eye-witnessed accounts of their formation are, to our knowledge, from Etna’s 1865 eruption. Although many of the literature
examples of lava trees and tree molds formed in pahoehoe, many of those reported in this work formed in a’a. The sites where
we have found the lava tree molds are located within the territory of the Etna Regional Park; most occur next to walking trails
and have a high potential for geotourism. 相似文献
55.
Solar empirical models based on regression of two variability indices for radiation from the photosphere and chromosphere
fit total solar irradiance (TSI) observations with accuracy comparable to the precision reported for the observations themselves.
However, the physical meaning of the fitting coefficients and their stability during different phases of the solar cycle has
not been examined in detail. We test the stability of the coefficients in regression models of the VIRGO TSI observations
over the nine years from the minimum of Cycle 23 in 1996 through the maximum to 2005. We also show how the coefficients converge
to the ‘`best fit’' using a search in the coefficient space. Analysis of TSI variability in different phases of this cycle
shows little change in regression models as long as the time periods used in the regression are long enough to show the slow
solar cycle variation in TSI. We extend our analysis to TSI observations from ERB, ACRIM2, ACRIM3, DIARAD, and TIM. The regression
models from these time series show large systematic differences in fitting coefficients for the plage and sunspot indices
that we used. These differences are significantly larger than the estimated uncertainties in the coefficients and point to
the difficulty of combining observations from different instruments to create an accurate composite TSI record over several
solar cycles. Our results clearly demonstrate the improvement in precision of TSI measurements from the Nimbus 7 ERB in Cycle
22 to the latest SORCE TIM data in Cycle 23. 相似文献
56.
This article describes a methodology to analyse debris-flow risk in the torrential watersheds of the southern hillside of
Gargano (Puglia—Italy). The approach integrates a stability model that identifies the areas of potential shallow landslides
in different meteorological conditions with a two-dimensional flood routing model that allows hazard mapping and GIS interface.
The results were combined with a susceptibility map that was defined by analyzing the vulnerability conditions and the exposure
of the alluvial fan. The models were calibrated on the 1972, July catastrophic event for which the distribution of rainstorm
intensity was available. The geo-mechanical properties of the debris were studied by field surveys and laboratory tests while
the sediment source areas and the shape of the alluvial cone were obtained using photo-aerial interpretation. The risk conditions
of the areas under consideration were also investigated in order to plan and guide measures aimed at limiting the damage such
hazards may cause. 相似文献
57.
Geomorphic and trench investigations are used toanalyze the seismic potential of the Aremogna-CinqueMiglia fault, an active N- to NW-trending, W-facingnormal fault located in Central Apennines. Wereconstructed a complex 16 km-long, as much as 6m-high, fault scarp that displaces late Holocenesediments in the Aremogna and Cinque Miglia basins.The complex surface expression of the fault, withdouble sub-parallel scarp sections, a change in strikeof about 40° and local complexity showingimportant horizontal component, appears to becontrolled by the presence of older tectoniclineaments. We opened two trenches across the faultscarp, used a quarry exposure, and reinterpreted atrench opened by Frezzotti and Giraudi (1989), to findthe geological evidence for three Holocene surfacefaulting earthquakes on the Aremogna-Cinque Migliafault. Based on radiocarbon dating and stratigraphicand climatic considerations timing of the events isconstrained between 800 B.C. and 1030 A.D., between3735 and 2940 B.C., and between 3540 and 5000 B.C.. The most recent event is not reported in the twomillennia-long Italian Catalogues of HistoricalSeismicity. We suggest that the most recent eventcould be one of the Middle Age earthquakes of unknownorigin for which several felt reports exist in Rome.Moreover, we also consider the hypothesis that one ofthe shocks of the ambiguous September 1349 earthquakesequence could be the Aremogna-Cinque Miglia mostrecent event. Anyway, based on historicalconsideration we indicate A.D. 1349 as the youngestpossible age for this event. Finally, we suggest theAremogna-Cinque Miglia fault is part of the easternsecondary Apennines seismogenic belt. The faultparameters we obtain for this fault (i.e., recurrence interval longer than 2000 yr, verticallong-term slip rate of 0.3–0.5 mm/yr and m 6.5–6.8 forthe event) can be used as a first hand reference tocharacterize the seismic behavior of other faultsalong this section of the Apennines. 相似文献
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60.
D. Raffaelli 《Marine pollution bulletin》1981,12(11):381-382
The usefulness of the ratio of two major meiofaunal taxa, nematodes and copepods, for marine pollution advocated by Raffaelli & Mason has been challenged by Coull, Hicks & Wells. The present paper answers their criticisms and provides additional information relevant for assessing the potential of this ratio for biomonitoring. 相似文献