Las invasiones bárbaras... (Una lectura irreverent)

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Le primitivisme dans la photographie : Hannah Höch – Orlan

L’impact des arts extra-européens sur la création photographique du xxesiècle n’est pas seulement né de la fascination exercée par les objets. Leurs images, telles qu’elles ont paru au sein de publications, eurent également des répercussions profondes sur la création. Durant la seconde moitié des années 1920, Hannah Höch, artiste dadaïste berlinoise, entreprit une série de photomontages combinant des fragments photographiques de masques et de sculptures non occidentaux aux caractères stéréotypés du pouvoir, du statut de la femme ou d’événements sociopolitiques qui ont marqué la presse illustrée de l’époque. Soixante-dix ans plus tard, l’artiste française Orlan débuta la série Self-Hybridations-Refigurations, fusionnant par les nouvelles technologies numériques l’image de sculptures précolombiennes et africaines à celle de son propre visage. Cette intervention mettra en perspective deux œuvres extraites de ces ensembles. Au regard des sources photographiques qui en sont à l’origine seront réfléchies les opérations par lesquelles leur sens a été déplacé vers un questionnement sur l’identité

Manganese content records seasonal upwelling in Lake Tanganyika mussels

International audienceBiogenic productivity of Lake Tanganyika is highly dependent on seasonal upwellings of cold, oxygen-depleted, nutrient-rich deep waters. We investigated the shell of freshwater bivalve Pleiodon spekii as a geochemical archive of these periodic hydrological changes tuned by the monsoon regime. The results of a three-year-long limnological and geochemical survey of the coastal waters performed on the dissolved and particulate fractions were compared to LA-ICP-MS profiles of Mn in five aragonitic shells from the same lake location. Three shells present very similar Mn/Ca profiles dominated by a peak that matched the concomitant increase of Mn and chlorophyll a in surface waters during the 2002 upwelling, while a shell collected during 2003 dry season detect both 2002 and 2003 upwelling events. Larger shells showing an extremely reduced growth display more than 8 Mn/Ca peaks suggesting at least an 8-year-record of seasonal changes in water composition. We postulate that Mn/Ca in shells record the conjunction of an increase of biological activity with supplied of dissolved Mn and nutriments in coastal waters, resulting in an enhanced assimilation of biogenic Mn-rich particles. By combining the most recent generation of laser ablation system and the powerful High Resolution ICP-MS, the spatial resolution could be improved down to 5 to 10 µm crater size and end up in a better constrain of the relative variations of the annual Mn peaks. Such an approach on P. spekii from Lake Tanganyika has definitively a great potential to provide recent and past records on primary productivity associated with the monsoon climate system

Mn seasonal upwellings recorded in Lake Tanganyika mussels

International audienceBiogenic productivity of Lake Tanganyika is highly dependent on seasonal upwellings of anoxic deep waters. We investigated the shell of freshwater bivalve Pleiodon spekii as a geochemical archive of these periodic hydrological changes tuned by the monsoon regime. The results of a 2-years-long geochemical survey of the coastal waters performed on the dissolved and particulate fractions were put in perspective against laser ablation ICP-MS profiles of Mn in five aragonitic shells from the same lake location. Skeletal Mn profiles in 3 shells are very similar and dominated by episodic peaks that matched the Mn increase recorded in surface waters during the 2002 upwelling, while a shell collected during 2003 dry season detect both 2002 and 2003 upwelling events. Larger shells showing an extremely reduced growth display more than 8Mn peaks suggesting at least an 8 years record of seasonal changes in water composition

Composition and seasonal variations in abundance of Copepod (Crustacea) populations from the northern part of Lake Tanganyika

peer reviewedCopepod has an important ecological role as a main food of several fishes on which commercial fisheries are based in Lake Tanganyika. However, very little multi-annual monitoring programs have been conducted for this group of crustacean zooplankton. This study was conducted in the northern part of Lake Tanganyika by weekly sampling at both pelagic and littoral sites over three consecutive years (2012–2014). The analyzed samples showed that Lake Tanganyika copepod was essentially composed of three suborders including Calanoida (30% by number) with a single endemic species, Cyclopoida (69%) with four dominant species and Harpacticoida (1%). These taxa showed variations in their abundance respectively at pelagic and littoral sampling sites. The average densities of copepods did slightly vary during the sampling period in both areas although higher peaks were observed in 2013. For the post-nauplii stage, Tropocyclops tenellus predominated while the nauplii of T. simplex predominated at both sampling sites. Seasonal fluctuations of copepod densities showed higher peaks in September/October and April/May, respectively, for the three most common species. T. simplex and M. aequatorialis ovigerous females showed higher peaks in the rainy season in 2013. These results can benefit pelagic fisheries research and lake environmental management efforts as the copepod abundance seems to be closely correlated to that of sardines in Lake Tanganyika. Copyright © 2016 AEHMS