Biodiversité marine

Résumé

La biodiversité marine est l'ensemble de la diversité biologique propre aux océans ou en dépendant très directement. Elle est en forte régression (du point de vue de la richesse trophique notamment) depuis plus de , incontestablement du fait des activités humaines et en particulier du fait de la surpêche et de la pollution et artificialisation des fleuves, estuaires, ports et zones côtières. thumb|left|Animaux marins. Planche extraite de Historiae naturalis de exanguibus aquaticis par Jan Jonston (1650) ; l'histoire naturelle a d'abord inventorié (décrit et classé) les espèces, puis l'écologie marine a montré l'importance des relations interspécifiques et entre les espèces et leur milieu, et l'importance de la diversité biologique dans les systèmes vivants, marins notamment. thumb|left|La diversité des espèces de la zone intertidale est significative, en dépit des conditions difficiles qui y règnent (déshydratation, brusques variations de salinité, exposition aux UV, chocs the

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https://fr.wikipedia.org/wiki/Biodiversit%C3%A9_marine

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Cours associés (9)

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

The students will learn the fundamentals in ecology with the goal to perceive the environment beyond its physical and chemical characteristics. Starting from basic concepts, they will acquire mechanistic understanding of biodiversity, ecosystem functioning and global change.

Le cours vise a familiariser les etudiants avec l'histoire de l'environnement et des paysages, et avec la maniere dont les preoccupations environnementales amenent a repenser aujourd'hui le sens et les principes de l'architecture et des disciplines de projet.

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Prediction and experimental evaluation of soil-water retention behavior of skeletal calcareous soils

Saeed Kouzegaran, Lyesse Laloui

Skeletal calcareous soils refer to soils consisting of skeletal remains of marine organisms. Although calcareous deposits are prevalent along coastal plains throughout the world, there is no study which investigates their behavior in unsaturated conditions. In these conditions, soil-water retention capacity is a fundamental parameter in relation to many geotechnical, environmental, and agricultural aspects. Water retention capacity of a soil is expected to be influenced by intra-particle pores unique to calcareous soils. Scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP) used in the current study clearly revealed this special microstructural characteristic. To study water retention and hydraulic hysteresis behavior of skeletal calcareous soil (obtained from the Hormuz Island of Iran) compared with a reference silicate soil (obtained from the Netherlands), a series of tests were conducted using pressure plate and controlled-suction oedometer apparatuses. Test results showed that in similar grain-size distribution of these soils, water retention curves of calcareous and silica soils are almost the same in low suctions, but calcareous soil retains more water at higher suctions due to its intra-particle voids. In addition, owing to these microstructural pores, ratio of Sr reduction on wetting path of a hysteresis loop was found to be more for calcareous soil than for silicate soil. Besides, to find and/or modify a prediction method for water retention curve of calcareous soil with acceptable accuracy, several existing pedotransfer functions were evaluated. Results showed that models proposed by Zapata et al. (Geotech Spec Publ 99:84–124, 2000) and Saxton et al. (Soil Science Society of America Journal 50(4): 1031–1036, 1986) after some simple modifications provide accurate estimations for water retention curve of calcareous soils.

2020

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Marine environments are frequently exposed to oil spills as a result of transportation, oil drilling or fuel usage. Whereas large oil spills and their effects have been widely documented, more common and recurrent small spills typically escape attention. To fill this important gap in the assessment of oil-spill effects, we performed two independent supervised full sea releases of 5 m(3) of crude oil, complemented by on-board mesocosm studies and sampling of accidentally encountered slicks. Using rapid on-board biological assays, we detect high bioavailability and toxicity of dissolved and dispersed oil within 24 h after the spills, occurring fairly deep (8 m) below the slicks. Selective decline of marine plankton is observed, equally relevant for early stages of larger spills. Our results demonstrate that, contrary to common thinking, even small spills have immediate adverse biological effects and their recurrent nature is likely to affect marine ecosystem functioning.

Nature Publishing Group2016

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Global change has caused a worldwide increase in reports of Vibrio-associated diseases with ecosystem-wide impacts on humans and marine animals. In Europe, higher prevalence of human infections followed regional climatic trends with outbreaks occurring during episodes of unusually warm weather. Similar patterns were also observed in Vibrioassociated diseases affecting marine organisms such as fish, bivalves and corals. Basic knowledge is still lacking on the ecology and evolutionary biology of these bacteria as well as on their virulence mechanisms. Current limitations in experimental systems to study infection and the lack of diagnostic tools still prevent a better understanding of Vibrio emergence. A major challenge is to foster cooperation between fundamental and applied research in order to investigate the consequences of pathogen emergence in natural Vibrio populations and answer federative questions that meet societal needs. Here we report the proceedings of the first European workshop dedicated to these specific goals of the Vibrio research community by connecting current knowledge to societal issues related to ocean health and food security.

Frontiers Research Foundation2015

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Prediction and experimental evaluation of soil-water retention behavior of skeletal calcareous soils

Saeed Kouzegaran, Lyesse Laloui

2020