Éditeur(s) : HAL CCSD Elsevier
Résumé : SUBSURF
Statistical sequential analysis was performed on a series of sediment cores collected from the Têt prodelta in the Gulf of Lions, northwestern Mediterranean Sea, between October 2003 and October 2004. Seabed changes during that period were correlated to hydrodynamic conditions (waves and currents) and river discharge. Low sediment supply prevents full preservation of new sediment strata on this low-accumulation prodelta located on a microtidal, storm-dominated inner shelf. Severe meteorological events caused a rapid succession of erosion and deposition phases. For example, the December 2003 flood and storm produced a flood layer deposit that persisted for 2 months with only slight transformations due to early diagenesis and/or bioturbation, until a new storm event eroded this layer. A typical sedimentary sequence was observed for the secular deposits composed of a 10-cm-thick sandy layer overlaying siltyclayey layers. These characteristic features were used to analyse the last millennia sedimentary record of the Têt prodelta. The low preservation of freshly deposited sediments and variable sedimentation rates during the last millennia period yield a sedimentary sequence formed by the outcropping of muddy prodeltaic units intersected by heterogeneous siltysandy units similar to those formed under present day hydrodynamic conditions. No flood layer was found related to catastrophic flooding of the last century in the sedimentary record. The Little Ice Age ( 1550–1850 AD) probably favoured the formation of a well-developed muddy prodelta in the mouth of the Têt River. Later on, the decrease of sediment supply by rivers due to climate change and/or human activities (damming, irrigation), and the increase of the number of high-energy storms reaching the coast, induced a coarsening of the top sediment layer on this prodelta. This modern change of the substrate is also observed in the composition of benthic biota found in the substrate
ISSN: 0025-3227

hal-00407662
https://hal.archives-ouvertes.fr/hal-00407662
DOI : 10.1016/j.margeo.2007.04.009

Éditeur(s) : HAL CCSD Public Library of Science
Résumé : International audience
Little information exists on the effects of ocean acidification (OA) on the digestive and post-digestive processes in marine fish. Here, we investigated OA impacts (Δ pH = 0.5) on the trophic transfer of select trace elements in the clownfish Amphiprion ocellaris using radiotracer techniques. Assimilation efficiencies of three essential elements (Co, Mn and Zn) as well as their other short-term and long-term kinetic parameters in juvenile clownfish were not affected by this experimental pH change. In complement, their stomach pH during digestion were not affected by the variation in seawater pH. Such observations suggest that OA impacts do not affect element assimilation in these fish. This apparent pCO2 tolerance may imply that clownfish have the ability to self-regulate pH shifts in their digestive tract, or that they can metabolically accommodate such shifts. Such results are important to accurately assess future OA impacts on diverse marine biota, as such impacts are highly species specific, complex, and may be modulated by species-specific metabolic processes.
ISSN: 1932-6203

hal-01564009
https://hal-univ-perp.archives-ouvertes.fr/hal-01564009
https://hal-univ-perp.archives-ouvertes.fr/hal-01564009/document
https://hal-univ-perp.archives-ouvertes.fr/hal-01564009/file/trophic%20transfer.pdf
DOI : 10.1371/journal.pone.0174344