Search results for "Reef"

Influence of artificial reefs on the surrounding infauna: Analysis of meiofauna

2002

We adopted a bottom-up approach in studying the effect of two artificial reefs in contrasting environmental conditions (sandy-mud and meso-eutrophic in the Adriatic Sea versus coarse sands and oligotrophic in the Tyrrhenian Sea) on the surrounding environment by assessing changes in the meiofauna. The spatial distribution of meiofaunal assemblages was established along a transect running from within each reef to well outside its direct sphere of influence, along with information on the trophic conditions of sediments (chloropigments, proteins, carbohydrates and total organic matter). Although total densities were significantly higher in the Adriatic than in the Tyrrhenian, the meiofauna dis…

A facies distribution model controlled by a tectonically inherited sea bottom topography in the carbonate rimmed shelf of the Upper Tithonian–Valangi…

2016

The Upper Tithonian–Valanginian shallow-water carbonates outcropping in the Palermo Mts (NW Sicily) consist of several facies associations reflecting different depositional environments of a carbonate rimmed shelf, pertaining to the Southern Tethyan continental margin. The reconstructed depositional model, based on the sedimentological features, cyclic facies arrangement and biota distribution, shows that a wide protected lagoon, dominated by algae, molluscs and scattered patch reefs, was bordered landward by a tidal flat, where stromatolitic algal mats were cyclically subaerial exposed, and seaward by a marine sand belt and reef complex. Oolitic packstone-grainstone lithofacies, cyclically…

New data on the Upper Triassic reefs of Western Sicily: stratigraphic constraints for the paleogeographic reconstruction of the Sicanian and Trapanes…

2005

Sea level rise in the Mediterranean Sea: High resolution constraints from vermetid reefs

2009

The Mediterranean Sea (MS), is extremely sensitive to rising sea-levels (SL) as attested by drowned archeological remains from the Roman Period [2]. Due to the absence of coral reefs, evidence for recent and Holocene SL change has so far mainly been restricted to coastal cores [1] archeological remains [2] and submerged speleothem deposits. Vermetid reefs are an extremely sensitive high resolution carbonate archive [3,4] and they are mainly formed in the lower intertidal zone by gregarious and sessile gastropods belonging to the genus Dendropoma (family Vermetidae). Since their interval of growth is restricted to the tidal zone, they can be used as precise SL proxies (about ±0.1 m in low ra…

Temporal dynamic of biofilms enhances the settlement of the central-Mediterranean reef-builder Dendropoma cristatum (Biondi, 1859).

2021

Abstract Research on marine invertebrate settlement provides baseline knowledge for restoration technique implementation, especially for biogenic engineers with limited dispersion ability. Previously, we determined that the maturity of a biofilm strongly enhances the settlement of the vermetid reef-builder Dendropoma cristatum. To elucidate settlement-related biofilm features, here we analyse the structure and composition of marine biofilms over time, through microscopic observations, eukaryotic and prokaryotic fingerprinting analyses and 16S rDNA Illumina sequencing. The vermetid settlement temporal increase matched with the higher biofilm coverage on the substratum and the reduction of th…

CONSERVATION NEEDS FOR THE VERMETID REEFS IN THE MEDITERRANEAN SEA

2015

Vermetid reefs are intertidal bioconstructions typical of many subtropical and temperate coastal areas worldwide. Distributed in the warmest waters of the Mediterranean Sea, the reefs are built by the vermetid gastropod Dendropoma petraeum and the coralline alga Neogoniolithon brassica-florida, two species included in the annexes of the Berna Convention. Vermetid reefs provide a wide set of ecosystem services, such as coastal protection from erosion, regulation of sediment transport and accumulation, serving as carbon deposit and increasing biodiversity at the intertidal level. Despite its vulnerability to several threats, such as pollution, spread of invasive species, ocean acidification a…

Discrimination of coral reflectance spectra in the Red Sea

2002

Benthic populations can potentially be mapped from remotely acquired spectral imagery, provided that they have distinctive reflectance signatures. We examined the spectral reflectance characteristics of 14 genera of Red Sea coral using a submersible spectroradiometer. Coral spectra varied quantitatively and qualitatively over the depth interval 5–20 m. Tissue pigment content had a larger effect on reflectance than colony morphology. Ten coral genera could be discriminated with a statistical probability of 52% on the basis of their absolute reflectance. Six groups of two to three coral genera could be discriminated with a probability of 60% on the basis of their rates of change in reflectanc…

Le Quaternaire franc-comtois. Essai chronologique et paléoclimatique.

1982

Le but de ce travail est d'établir le cadre chronologique et paléoclimatique du Quaternaire en Franche-Comté à partir de l'étude des formations édifiées au cours de cette période.Deux grands types de dépôts ont été plus particulièrement étudiés: ·- Les remplissages karstiques d'avens, de porches de grottes et d'abris sous roche, donnant un éclairage intense, mais ponctuel, de l'environnement physique et biologique, grâce aux faunes abondantes et aux indices climatiques d'ordre sédimentologique.- Les dépôts glaciaires et paraglaciaires (moraines, fluvioglaciaires, glacio-lacustres) qui permettent de situer des coupures climatiques au cours du temps dans l'espace géographique étudié.L'étude d…

Hyperbolic actions of the multiplicative group on affine varieties : exotic spaces and local structures

2015

This thesis is devoted to the study of affine T-varieties using the Altmann-Hausen presentation. We are especially interested in the case of hyperbolic actions of the multiplicative group Gm. In the first part, exotic affine spaces are studied, that is, smooth contractible affine varieties, assuming in addition that they are endowed with a Gm-action. In particular, in the case of dimension 3, we reinterpret the construction of Koras-Russell threefolds in terms of polyhedral divisors andwe give constructions of smooth contractible affine varieties and in dimensionslarger than 3.In the second part we consider the property of G-uniform rationality for a G-variety. This means that every point o…

Demonstration of a reef knot microfiber resonator.

2009

We propose a new way to realize a microfiber optical resonator by implementing the topology of a reef knot using two microfibers. We describe how this structure, which includes 4 ports and can serve as an add-drop filter, can be fabricated. Resonances in an all-silica reef knot are measured and good fits are obtained from a simple resonator model. We also show the feasibility of assembling a hybrid silica-chalcogenide reef knot structure.