Search results for "Reef"

The role of topography and erosion in the development and architecture of shallow-water coral bioherms (Tortonian-Messinian, Cabo de Gata, SE Spain).

2009

23 pages; International audience; During the Miocene, Mediterranean shallow-water carbonates were rich in scleractinian corals, which thrive in various depositional settings. A Tortonian–Messinian bioherm belt developing in a heterozoan-dominated ramp was investigated along a 1.2 km continuous transect located in the Cabo de Gata region. The interval studied displays four depositional environments from mid-to-inner ramp, dominated by swell waves and storm energy, deposited as a single, large-scale depositional sequence during a 3rd to 4th order transgressive–regressive cycle. The bioherms grew in three phases, and were essentially composed of inplace primary frameworks. Three coral genera w…

Biological diversity of the microbial film associated to the central-Mediterranean Dendropoma cristatum (Biondi, 1859) reefs.

2017

Microbial films may provide physical and bio-chemical cues which positively affect the settlement dynamic of a variety of benthic marine organisms, driving the development of ecosystems. Also for the Mediterranean intertidal reef-builder Dendropoma cristatum (Biondi, 1859), biofilm maturity has been found to enhance the settlement pattern. However, the microbial diversity associated with these bioconstructions has never been described. This study investigates the D. cristatum reef bacterial assemblage composition and temporal evolution in two localities in the northwest of Sicily. Biological diversity of the reef-associated biofilm and of 3 progressively older biofims obtained on artificial…

Microbial deposits in the aftermath of the end-Permian mass extinction: A diverging case from the Mineral Mountains (Utah, USA)

2015

40 pages; International audience; The Lower Triassic Mineral Mountains area (Utah, USA) preserves diversified Smithian and Spathian reefs and bioaccumulations that contain fenestral-microbialites and various benthic and pelagic organisms. Ecological and environmental changes during the Early Triassic are commonly assumed to be associated with numerous perturbations (productivity changes, acidifica-tion, redox changes, hypercapnia, eustatism and temperature changes) post-dating the Permian–Triassic mass extinction. New data acquired in the Mineral Mountains sediments provide evidence to decipher the relationships between depositional environments and the growth and distribution of microbial …

Experimental investigation on a geocontainer submerged reef

2014

Geotextile sand containers (GSC) have been used as permanent construction elements in coastal works for more than 20 years,becoming more and more popular as an alternative to the most typical coastal structures. Aim of this work is to analyze the hydrodynamic, stability and morphodynamic response of a GSC submerged reef by means of an experimental campaign. The first investigated aspect concerned the hydrodynamics. The reflection and transmission coefficients for regular and random waves were determined: the reflection coefficient decreases with increasing of kh; the transmission coefficient decreases with the increase of the incident wave. As regards the stability of the structure, it was …

APPROCCIO MULTIDISCIPLINARE ALLO STUDIO DELLE BIOCOSTRUZIONI DI Sabellaria sp. (Annelida: Polychaeta) NEL MEDITERRANEO E ALLA FAUNA AD ESSE ASSOCIATA

The use of very high-resolution images for mapping of Posidonia oceanica reef

2020

Posidonia oceanica is an endemic Mediterranean seagrass that forms wide and dense meadows from the surface up to about 40 m depth. P. oceanica can develop on matte, a typical terraced structure built up by itself, consisting of intertwined rhizomes, roots and sediment, which may allow shoots to reach the sea surface, where may form typical reefs (récif barrière) considered “natural monuments”. These structures have received increasing attention for the potential ecosystem services they provide in protecting the coasts from erosion, forming new habitats (coastal lagoons) and contributing to carbon sink. P. oceanica reefs are particularly exposed to the expected increase in temperature and to…

Hurwitz spaces of quadruple coverings of elliptic curves and the moduli space of abelian threefolds A_3(1,1,4)

2005

We prove that the moduli space A_3(1,1,4) of polarized abelian threefolds with polarization of type (1,1,4) is unirational. By a result of Birkenhake and Lange this implies the unirationality of the isomorphic moduli space A_3(1,4,4). The result is based on the study the Hurwitz space H_{4,n}(Y) of quadruple coverings of an elliptic curve Y simply branched in n points. We prove the unirationality of its codimension one subvariety H^{0}_{4,A}(Y) which parametrizes quadruple coverings ��:X --> Y with Tschirnhausen modules isomorphic to A^{-1}, where A\in Pic^{n/2}Y, and for which ��^*:J(Y)--> J(X) is injective. This is an analog of the result of Arbarello and Cornalba that the Hurwitz s…

Hurwitz spaces of triple coverings of elliptic curves and moduli spaces of abelian threefolds

2002

We prove that the moduli spaces A_3(D) of polarized abelian threefolds with polarizations of types D=(1,1,2), (1,2,2), (1,1,3) or (1,3,3) are unirational. The result is based on the study of families of simple coverings of elliptic curves of degree 2 or 3 and on the study of the corresponding period mappings associated with holomorphic differentials with trace 0. In particular we prove the unirationality of the Hurwitz space H_{3,A}(Y) which parameterizes simply branched triple coverings of an elliptic curve Y with determinants of the Tschirnhausen modules isomorphic to A^{-1}.

Biodiversità associata ai reef a vermeti: effetti dell'acidificazione sulla malacofauna

2014

La continua e prevista Acidificazione degli Oceani (AO) potrebbe rappresentare un ampio fattore di stress per molti organismi marini, soprattutto calcificanti. La principale causa dell’acidificazione degli oceani è legata all’aumento della CO₂ antropogenica. I Reef a Vermeti, a causa della loro eterogeneità, la locazione intertidale e gli alti livelli di biodiversità che supportano, rappresentano un Habitat chiave in Mediterraneo. Attraverso un esperimento di trapianto sono state valutate possibili variazioni in composizione e struttura del popolamento a molluschi associato lungo un gradiente naturale di pH.

Rekomendācijas aizsargājamās jūras teritorijas "Rīgas līča rietumu piekraste" monitoringa metožu uzlabošanai

2021

Akmeņu sēkļi ir svarīgi jūras vides bioloģiskās daudzveidības un kvalitātes nodrošināšanai – tie ir mājvieta gan daudzām sēdošām un peldošām bentisko jūras dzīvnieku un aļģu sugām, gan nozīmīga nārsta vieta zivju sugām. Dažādu abiotisko faktoru ietekmē akmeņu sēkļos nereti veidojas mikrobiotopi vai atšķirīgi biotopu kompleksi, kas savas mozaīkveida struktūras, kā arī mainīgā dziļuma dēļ apgrūtina šo aizsargājamo jūras biotopu monitoringu. Šo apgrūtinājumu dēļ nepieciešams uzlabot monitoringa metožu efektivitāti un rekomendēt tādas monitoringa metodes, kas pietiekami atspoguļotu teritorijas bioloģisko daudzveidību. Galvenās rekomendācijas monitoringa uzlabošanai, būtu veikt monitoringu staci…