Grande Barrière de corail

La Grande Barrière de corail ou récif de la Grande Barrière (en Great Barrier Reef) constitue le plus grand récif corallien du monde. L'ensemble, qui s'étire sur plus de depuis Bundaberg jusqu'à la pointes de la péninsule du cap York, couvre une superficie de . Le site est inscrit en 1981 sur la liste du patrimoine mondial de l'Unesco sous le nom de Grande Barrière. La Grande Barrière de corail, située en mer de Corail au large du Queensland, en Australie, est composée de et . Visible de l'espace, elle est la plus grande structure vivante biogénique (créée par des organismes vivants) au monde, construite par des milliards d'organismes minuscules, connus en tant que coraux polypes ; à ce titre, elle soutient une large diversité de vie marine. La chaîne de télévision CNN la labellise comme une des Sept merveilles du monde. Le Queensland National Trust la nomme comme l'une des icônes du Queensland. Une large partie du récif est protégée par le parc marin de la Grande Barrière, qui a

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Comparative bioaccumulation of trace elements between Nautilus pompilius and Nautilus macromphalus (Cephalopoda: Nautiloidea) from Vanuatu and New Caledonia

Julien Boucher

The concentrations of 16 trace elements were investigated and compared for the first time in the digestive and excreting tissues of two Nautilus species (Cephalopoda: Nautiloidea) from two geologically contrasted areas: (1) N. macromphalus from New Caledonia, a region characterized by its richness in nickel ores and its lack of tectonic activities and (2) N. pompilius from the Vanuatu archipelago showing high volcanic and tectonic activities. In both Nautilus species, results clearly highlighted that the digestive gland played a key role in the bioaccumulation and storage of Ag, Cd, Ce, Co, Cu, Fe, La, Nd, V, and Zn whereas As, Cr, Mn, Ni, Pb, and Se were accumulated in a greater extent in the excreting tissues (i.e. pericardial and renal appendages). Despite contrasting environments, no significant difference (p

2009

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Assessing debris flow impact on flexible ring net barrier: A coupled CFD-DEM study

Xingyue Li

Flexible ring net barriers have become increasingly popular in practical mitigation of debris flow worldwide. Systematic assessments of their response and performance subjected to the impact of realistic debris flows remain challenging. This study presents a novel computational approach based on coupled CFD-DEM to model the impact of debris flow on a flexible ring net barrier in a unified framework. The debris flow is treated as a solid-fluid mixture, where the solid phase and the fluid phase are modeled by DEM and CFD, respectively. The barrier is simulated as a system of different deformable components, including rings, cables and energy dissipators, and is modeled with DEM. The proposed method expedites a convenient, unified consideration of multi-way interactions among the debris solid, the debris fluid, and the barrier. The simulation of a flexible barrier is calibrated against existing experimental data and past numerical results, by examining the quasi-static responses of different barrier components and the dynamic reactions of the entire barrier. The barrier system is further subjected to the impact of debris flows with different Froude numbers to examine its performance, in terms of its retaining capacity of debris mass and peak sustained forces in the barrier. Two energy-related indices, energy dissipation ratio and energy absorption ratio, are estimated for design reference. The study provides a novel, physically based predictive computational tool for future design and analysis of flexible ring net barriers in debris flow mitigation.

2020

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Intestinal Fish Cell Barrier Model to Assess Transfer of Organic Chemicals in Vitro: An Experimental and Computational Study

Jenny Maner, Kristin Schirmer, Hannah Inka Schug, Anze Zupanic

We studied the role of the fish intestine as a barrier for organic chemicals using the epithelial barrier model built on the rainbow trout (Oncorhynchus mykiss) intestinal cell line, RTgutGC and the newly developed exposure chamber, TransFEr, specifically designed to work with hydrophobic and volatile chemicals. Testing 11 chemicals with a range of physicochemical properties (logK(ow): 2.2 to 6.3, logHLC: 6.1 to 2.3) and combining the data with a mechanistic kinetic model enabled the determination of dominant processes underlying the transfer experiments and the derivation of robust transfer rates. Against the current assumption in chemical uptake modeling, chemical transfer did not strictly depend on the logK(ow) but resulted from chemical-specific intracellular accumulation and biotransformation combined with paracellular and active transport. Modeling also identified that conducting elaborate measurements of the plastic parts, including the polystyrene insert and the PET filter, is unnecessary and that stirring in the TransFEr chamber reduced the stagnant water layers compared to theoretical predictions. Aside from providing insights into chemical uptake via the intestinal epithelium, this system can easily be transferred to other cell-based barrier systems, such as the fish gill or mammalian intestinal models and may improve in vitro-in vivo extrapolation and prediction of chemical bioaccumulation into organisms.

AMER CHEMICAL SOC2019

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Récif corallien

thumb|upright=1.5|Le corail, dont les colonies forment les récifs. thumb|upright=1.5|Colonie d’Acropora pulchra. Un récif corallien ou barrière de corail est une structure naturelle bioconstruite à l

Corail

Le terme corail désigne un certain nombre d'animaux marins appartenant à l'embranchement des cnidaires, caractérisés par leur squelette dur. Dans un sens restreint cette appellation est utilisée par

Élévation du niveau de la mer

L' est un phénomène observable au niveau mondial depuis le début du , qui résulte du réchauffement climatique. Le niveau moyen des océans augmente de entre 1901 et 2018, la moitié de cette hausse

ENV-406: Biomineralization: from nature to application

Understanding process and role of biomineralization (minerals formed by living organisms) in context of Earth's evolution,global chemical cycles, climatic changes and remediation.