Search results for "Shallow"
showing 10 items of 144 documents
Factors controlling hydrochemical and trophic state variables in 86 shallow lakes in Europe
2003
In order to disentangle the causes of variations in water chemistry among European shallow lakes, we performed standardised sampling programs in 86 lakes along a latitudinal gradient from southern Spain to northern Sweden. Lakes with an area of 0.1 to 27 000 ha and mean depth of 0.4–5.6 m located in low to high altitudes were investigated within the EC project ECOFRAME 1–4 times during June–October 2000–2001. Several variables like conductivity, alkalinity, abundance of submerged plants, concentrations of suspended solids, total nitrogen and phosphorus were latitude-dependent decreasing from south to north. Secchi depth, concentrations of total nitrogen, total phosphorus, suspended solids, …
The shallow seagrass system in Southern Mediterranean (Sicily, Italy): a large sink of organic matter available to upper consumers.
2006
The effects of human activities related to salt production on the global complexity of a shallow hyperhaline system (Sicily, Italy) were investigated. This through monitoring dynamics of some physical, chemical and trophic factors recognised as main constraints for the origin of organic matter and its availability to apex consumers. The system was dominated by seagrass Ruppia cirrhosa and large stands of macroalga Chaetomorpha linum; isopods and gasteropods were the most abundant taxa among benthic organisms, while Aphanius fasciatus and Atherina boyeri represented up to 90% of all catch among the small resident fishes. Ruppia could function as a multidimensional framework able to increase …
A coupled stability and eco-hydrological model to predict shallow landslides
2011
Knowledge of spatio-temporal dynamics of soil water content, groundwater and infiltration processes is of considerable importance for the understanding and prediction of landslides. Rainfall and consequent water infiltration affect slope stability in various ways, mainly acting on the pore pressure distribution whose increase causes a decrease of the shearing resistance of the soil. For such reasons rainfall and transient changes in the hydrological systems are considered the most common triggers of landslides. So far, the difficulty to monitor groundwater levels or soil moisture contents in unstable terrain have made modeling of landslide a complex issue. At the present, the availability o…
Shallow ocean oxygen decline during the end-Triassic mass extinction
2022
The end-Triassic mass extinction (ETME) was associated with intensified deep-water anoxia in epicontinental seas and mid-depth waters, yet the absolute oxygenation state in the shallow ocean is uncharacterized. Here we report carbonate-associated iodine data from the peritidal Mount Sparagio section (Southern Italy) that documents the ETME (~ 200 Ma) in the western Tethys. We find a sharp drop in carbonate I/(Ca + Mg) ratios across the extinction horizon and persisting into the Early Jurassic. This records local dissolved oxygen and iodate decline in the near-surface ocean of low-latitude Tethys due to the development of depleted oxygen concentrations. Consequently, during the ETME even sha…
Approximate Osher–Solomon schemes for hyperbolic systems
2016
This paper is concerned with a new kind of Riemann solvers for hyperbolic systems, which can be applied both in the conservative and nonconservative cases. In particular, the proposed schemes constitute a simple version of the classical Osher-Solomon Riemann solver, and extend in some sense the schemes proposed in Dumbser and Toro (2011) 19,20. The viscosity matrix of the numerical flux is constructed as a linear combination of functional evaluations of the Jacobian of the flux at several quadrature points. Some families of functions have been proposed to this end: Chebyshev polynomials and rational-type functions. Our schemes have been tested with different initial value Riemann problems f…
Flow resistance ofPosidonia oceanicain shallow water
2006
Management of coastal waters and lagoons by mathematical circulation models requires determination of the hydraulic resistance of submerged vegetation. A plant typical of sandy coastal bottoms in the Mediterranean Sea is Posidonia oceanica, which is constituted by very thin and flexible ribbon-like leaves, about 1 cm wide and up to 1.5 m long, and usually covers the bottom with a density of 500-1000 plants/ m2. From the hydraulic viewpoint, P. oceanica constitutes a particular roughness, because, as the velocity increases, the leaves bend more and more until they lie down on the bottom. Although P. oceanica is widespread, in the technical literature it is difficult to find indications about…
Eustasy and sea water Sr composition: application to high-resolution Sr-isotope stratigraphy of Miocene shallow-water carbonates
2007
Oceanic 87 Sr/ 86 Sr-isotope ratios are strongly influenced by rates of silicate weathering and therefore linked not only to glaciation but also to sea-level change. The present study combines analysis of sequence stratigraphy and basin architecture with Sr-isotope stratigraphy in Miocene shallow-water sediments in southern Portugal and Crete (Greece). The common method is to use smoothed global sea water Sr-isotope reference curves but here a different approach is chosen. Instead, measured Sr-isotope curves are correlated with unsmoothed reference curves by identification of similar fluctuations in the order of several 100 kyr. Transgressive intervals are characterized by increasing Sr-iso…
The genus Ruppia L. (Ruppiaceae) in the Mediterranean region: An overview
2015
Abstract This paper reviews the current knowledge on the diversity, distribution and ecology of the genus Ruppia L. in the Mediterranean region. The genus Ruppia, a cosmopolitan aquatic plant complex, is generally restricted to shallow waters such as coastal lagoons and brackish habitats characterized by fine sediments and high salinity fluctuations. In these habitats Ruppia meadows play an important structural and functional role. Molecular analyses revealed the presence of 16 haplotypes in the Mediterranean region, one corresponding to Ruppia maritima L., and the others to various morphological forms of Ruppia cirrhosa (Petagna) Grande, all together referred to as the “R. cirrhosa s.l. co…
Simulation of the Propagation of Tsunamis in Coastal Regions by a Two-Dimensional Non-Hydrostatic Shallow Water Solver
2017
Due to the enormous damages and losses of human lives in the inundated regions, the simulation of the propagation of tsunamis in coastal areas has received an increasing interest of the researchers. We present a 2D depth-integrated, non- hydrostatic shallow waters solver to simulate the propagation of tsunamis, solitary waves and surges in coastal regions. We write the governing continuity and momentum equations in conservative form and discretize the domain with unstructured triangular Generalized Delaunay meshes. We apply a fractional- time-step procedure, where two problems (steps) are consecutively solved. In the first and in the second step, we hypothesize a hydrostatic and a non-hydro…
Asociaciones de Ostrácodos del Mioceno Temprano—Medio de Loma Negra (Bardenas Reales de Navarra, Cuenca del Ebro): Evolución Paleoambiental de un Med…
2014
LOWER-MIDDLE MIOCENE OSTRACOD ASSEMBLAGES OF LOMA NEGRA (BARDENAS REALES DE NAVARRA, EBRO BASIN): PALAEOENVIRONMENTAL EVOLUTION OF A LACUSTRINE SYSTEM. The palaeoenvironmental evolution of the Loma Negra section (Bardenas Reales de Navarra, Ebro Basin) during the lower-middle Miocene, is studied for the first time. The paleoen- vironmental interpretation is based on the recovered ostracod assemblages and the sedimentology. The lower part of this section is composed by red, yellow and grey mudstones, and with Paralimnocythere sp. as the most abundant ostracod taxon. The lithological features and the fau- nistic assemblage allows the interpretation of a paleoenvironment with the development o…