Éditeur(s) : HAL CCSD
Résumé : International audience
Philodendron acutatum (Araceae) is a hemiepiphyte common to the Atlantic Forest of northeastern Brazil. In two localities, we studied the species’ breeding system and associations with flower-visiting insects, along with an analysis of its floral scent composition. The fruit set of self-incompatible P. acutatum was high, more than 90%, and inflorescences were exclusively pollinated by one species of scarab beetle, Cyclocephala celata (Scarabaeidae, Dynastinae). Pollinators are drawn toward the inflorescences at dusk by strong floral fragrancesgiven off during the female phase of anthesis, along with endogenous heating of the spadix, whose temperatures were recorded at more than 11C above ambient air. Two other species of flower-visiting Cyclocephala were also consistently recovered in blacklight trappings during the flowering period of P. acutatum. The fact that only C. celata was found in association with P. acutatum suggests a local reproductivedependence of the plant to this scarab beetle species. Dihydro-b-ionone and 2-hydroxy-5-methyl-3-hexanone, a rare volatile molecule so far unreported as a floral compound, together accounted for more than 97% of the unique scent composition of P. acutatum and might be involved in specific attraction of C. celata.
International Journal of Plant Sciences

hal-01094225
https://hal-agroparistech.archives-ouvertes.fr/hal-01094225
DOI : 10.1086/654846

Éditeur(s) : Inter-research
Résumé : Chemical tracers (e. g. stable isotopes or trace metals) are increasingly used to study trophic ecology and feeding habits of marine organisms and various factors can affect their values. The aim of the present study was to provide information on ontogenic effects on stable carbon and nitrogen values (delta C-13 and delta N-15) and on cadmium (Cd) and mercury (Hg) concentrations in 5 cephalopod species from the Bay of Biscay (North-East Atlantic Ocean). To this end, individuals belonging to 3 species showing the widest range of sizes were analysed for muscle delta C-13 and delta N-15 values and muscle Hg, and digestive gland Cd concentrations. Results showed that stable isotope ratios allowed discrimination of specific feeding strategies during ontogenesis. Segregation between 5 cephalopod species in terms of trophic ecology was also evidenced (different isotopic niches). In contrast, Hg concentrations varied over the same order of magnitude in these 5 cephalopod species, despite higher levels in the benthic octopus Eledone cirrhosa. Consistently, Hg concentrations followed the same ontogenic pattern and increased with increasing body size/age of cephalopods. Finally, Cd concentrations varied over 3 orders of magnitude among the 5 species. Despite possible effects of physiology in terms of metal bioaccumulation, Cd concentrations were likely to reflect specific feeding preferences or feeding zones and ontogenic variability within a single species. Thus, ontogenic effects have to be taken into account when stable isotope ratios of carbon and nitrogen or trace metals are used as ecological tracers; the best recommendation being to focus on a given class age.
Marine Ecology Progress Series (0171-8630) (Inter-research), 2011 , Vol. 433 , P. 107-120

Droits : Inter-Research 2011 · www.int-res.com
http://archimer.ifremer.fr/doc/00166/27761/25938.pdf
DOI:10.3354/meps09159
http://archimer.ifremer.fr/doc/00166/27761/

Éditeur(s) : Amer Geophysical Union
Résumé : This study focuses on the improved estimation of mesoscale surface ocean circulation obtained by merging TOPEX/Poseidon (T/P) and ERS-1 and -2 altimeter measurements between October 1992 and May 1998. Once carefully intercalibrated and homogenized, these data are merged through an advanced global objective analysis method that allows us to correct for residual long wavelength errors and uses realistic correlation scales of ocean dynamics, The high-resolution (0.25 degrees x 0.25 degrees) merged T/P + ERS-1 and -2 sea level anomaly maps provide more homogeneous and reduced mapping errors than either individual data set and more realistic sea level and geostrophic velocity statistics than T/P data alone. Furthermore, the merged T/P + ERS-1 and -2 maps yield eddy kinetic energy (EKE) levels 30% higher than maps of T/P alone. They also permit realistic global estimates of east and north components of EKE and their seasonal variations, to study EKE sources better. A comparison of velocity statistics with World Ocean Circulation Experiment surface drifters in the North Atlantic shows very good agreement. Comparison with contemporary current meter data in various oceanic regimes also produces comparable levels of energy and similar ratios of northward and eastward energy, showing that the maps are suitable to studying anisotropy. The T/P + ERS zonal and meridional components of the mapped currents usually present comparable rms variability, even though the variability in the Atlantic is more isotropic than that in the Pacific, which exhibits strong zonal changes. The EKE map presents a very detailed description, presumably never before achieved at a global scale. Pronounced seasonal changes of the EKE are found in many regions, notably the northeastern Pacific, the northeastern and northwestern Atlantic, the tropical oceans, and the zonally extended bands centered near 20 degrees S in the Indian and western Pacific Oceans and at 20 degrees N in the northwestern nl Pacific.
Journal Of Geophysical Research-oceans (0148-0227) (Amer Geophysical Union), 2000-08 , Vol. 105 , N. C8 , P. 19477-19498

Droits : 2000 AGU
http://archimer.ifremer.fr/doc/00079/19033/16617.pdf
DOI:10.1029/2000JC900063
http://archimer.ifremer.fr/doc/00079/19033/

Éditeur(s) : HAL CCSD
Résumé : The Neogene geodynamics evolution of the south-Alboran realm in western Mediterranean has been clarified, based on sedimentological and chronostratigraphical studies. This work focuses on three main themes of research, the first is to establish the moments for the opening and closing of the North Rifian Corridor by studying two Neogene basins of the southern edge of the Alboran sea. The second, aims to understand the behavior of these two basins face a major event in the history of the Mediterranean: The Messinian Salinity Crisis. Finally, the third theme aims to understand the modalities Post-MSC reflooding in the southern part of the Alboran realm.The late Miocene evolution of the North Rifian Corridor is clarified on the basis of chronostratigraphic studies of the Neogene Boudinar and Arbaa Taourirt basins (northeastern Morocco). The marine sediments deposited in the Boudinar basin between the early Tortonian and the late early Messinian (10 Ma to 6.1 Ma) and in the late Tortonian-earliest Messinian interval in the Arbaa Taourirt basin. Palaeoenvironmental data record a major drowning in association with extensive tectonics in the Boudinar basin during the early Messinian at ~7.2 Ma. At the same time, prograding conglomerates and sandstones developed over the late Tortonian marls in the Arbaa Taourirt basin. During the late-early Messinian, a shallowing trend occurred in the Boudinar basin. Thus, the North Rifian Corridor opened at ~7.2 Ma ensuring Atlantic-Mediterranean connections, then was progressively restricted during the late-early Messinian and totally closed at ~6.1 Ma. New sedimentological and paleontological studies of the late Messinian-early Pliocene deposits in the Boudinar basin provide new information on the Messinian Salinity Crisis (« MSC ») and the Zanclean reflooding in the Alboran sea. The Messinian erosional surface « MES » is of late Messinian age and was emplaced in subaerial settings. It is polygenic, its original geometry is locally preserved and was re-shaped by the Pliocene transgressive surface. Above the « MES », the Boudinar basin infill is characterized by a wide variety of facies from continental settings to lower offshore conditions. Two major sets are recognized: a latest Messinian-Zanclean set that constitutes a transgressive-regressive megasequence interrupted at the top by a tectonic unconformity, and an Plio-Quaternary regressive set. During the late Messinian Zanclean interval, four successive depositional models were documented. They record major changes in palaeoflow and paleogeography related to base-level fluctuations. No Gilbert-type delta has ben identified at Boudinar. the beginning of base-level rise is marked by normal regressions and by the formation of several lacs and fan-delta complexes on the margins of the basin in the late Messinian and befor the marine reefloding in the early Zanclean. The marine reflooding of the basin appears later, with a transgressive surface of ravinment and a thick package of transgressive deposits. These transgressive deposits onlap over all previous deposits. The major part of the basin infill did not issue from an inner landward position (south of the basin) but from the northwestern side of the basin, i.e. near the Mediterranean. Sediments were subsequently reworked by storms and transported by longshore-drift towards the south. a maximum flooding surface is found several tens of metres above the « MES ». This fiding is consistent with a progressive and not a catastrophic early Zanclean flooding of the westernMediterranean after the Mediterranean base-level fall.
Sur la base d’études sédimentologiques et chronostratigraphiques dans les bassins de Boudinar et d’Arbaa Taourirt (Rif oriental, Maroc), l’évolution géodynamique néogène du domaine sud-Alboran en Méditerranée occidentale a été clarifiée. Ce travail est axé sur trois grandes thématiques de recherche. La première vise à l’établissement d’un cadre chronostratigraphique pour l’ouverture et la fermeture du Couloir Nord Rifain, par l’étude de deux bassins nèogènes de la bordure sud de la mer d’Alboran. La deuxième, vise à comprendre le comportement de ces deux bassins face à un événement majeur de l’histoire de la Mediterranée : la Crise de salinité messinienne. Finalement, la troisième vise à comprendre les modalités de remise en eau de la Méditerranée après la Crise : le reenoiement pliocène. L'évolution du Couloir Nord Rifain au Miocène supérieur est clarifiée sur la base des études chronostratigraphiques des bassins néogènes de Boudinar et d'Arbaa Taourirt (Maroc Nord oriental). Les sédiments marins miocènes se sont déposés entre le Tortonien inférieur et le Messinien inférieur (10 à 6.1 Ma) dans le bassin de Boudinar et entre le Tortonien supérieur et le Messinien inférieur dans le bassin d'Arbaa Taourirt. Les données paléoenvironnementales enregistrent un ennoyage important du bassin de Boudinar en relation avec une tectonique extensive pendant le Messinien inférieur (~7.2 Ma). En même temps, des conglomérats et de grès progradants se sont développés au-dessus des marnes tortoniennes dans le bassin d’Arbaa Taourirt. Le bassin de Boudinar a subi un désapprofondissement au Messinien inférieur. Ces résultats indiquent que le Couloir Nord Rifain s’est ouvert à ~7.2 Ma assurant les communications entre l’Atlantique et la Méditerranée, puis a subi une restriction progressive pendant le Messinien inférieur avant d’être totalement fermé à ~6.1 Ma.De nouvelles études sédimentologiques et paléontologiques des dépôts Messinien supérieur-Pliocène inférieur dans le bassin de Boudinar fournissent des informations sur la Crise de salinité messinienne (« MSC ») et le réennoiement zancléen dans la Mer d'Alboran. L’un des marqueurs majeurs de la Crise est identifié : la surface d’érosion messinienne « MES ». Elle est d'âge Messinien supérieur et a été mise en place dans des conditions subaériennes. Sa géométrie originale n’est préservée que localement et a été remodelée par la surface transgressive du Pliocène inférieur. Au dessus de la « MES » le remplissage sédimentaire du bassin de Boudinar est caractérisé par une grande variété de faciès allant des conditions de dépôts continentales jusqu’à des conditions d’offshore inférieur. Deux ensembles majeurs sont reconnus : un ensemble messinien terminal-zancléen qui constitue une mégaséquence transgressive-regressive, interrompue au sommet par une discordance tectonique, et un ensemble plio-quaternaire regressif. Durant l’intervalle Messinien terminal-Zancléen, quatre modèles de dépôts successifs ont été documentés enregistrant des changements majeurs de paléocourants et de paléogéographies, liés aux fluctuations de niveau de base. Nous n’avons pas identifié de Gilbert delta à Boudinar. La remontée du niveau de base est marquée par une régression normale et par le développement des lacs et de complexes de fan-deltas sur les marges du bassin pendant le Messinien supérieur, avant l’inondation marine au Zancléen basal. Le réennoiement marin du bassin apparait plus tard avec une surface de transgression ravinante et par d’épais dépôts transgressifs, en onlap sur tous les dépôts précédents. La majeure partie du remplissage sédimentaire du bassin n’est pas reçue des reliefs de la bordure sud du bassin, mais du côté Nord-Ouset au bord de la Méditerranée. Les sédiments sont alors remaniés par les tempêtes et transportés vers le sud par la dérive littorale. Une surface d’inondation maximale a été identifiée à plusieurs dizaines de mètres au-dessus de la « MES ». Ceci suggère un ennoiement progressif et non catastrophique, après la chute du niveau de base méditerranéen.
https://tel.archives-ouvertes.fr/tel-01473572

Droits : http://hal.archives-ouvertes.fr/licences/copyright/
tel-01473572
https://tel.archives-ouvertes.fr/tel-01473572
https://tel.archives-ouvertes.fr/tel-01473572/document
https://tel.archives-ouvertes.fr/tel-01473572/file/Th%C3%A8se-achalhi.pdf