Live (stained) benthic foraminifera from the Cap-Ferret Canyon (Bay of Biscay, NE Atlantic): A comparison between the canyon axis and the surrounding areas P. Duros a,n , C. Fontanier a,b , E. Metzger a , F. Cesbron a , B. Deflandre b , S. Schmidt b , R. Buscail c , S. Zaragosi b , P. Kerherve ´ c , S. Rigaud d , M.-L. Delgard b , F.J. Jorissen a a LUNAM Universite´, Universite´ d’Angers, UMR CNRS 6112 LPGN-BIAF, Laboratoire des Bio-Indicateurs Actuels et Fossiles, 2 Boulevard Lavoisier, 49045 Angers Cedex, France b UMR 5805 Environnements et Pale´oenvironnements Oce´aniques (EPOC-OASU), University of Bordeaux I, Avenue des Faculte´s, 33405 Talence Cedex, France c CNRS, Centre de Formation et de Recherche sur les Environnements Me ´diterrane´ens, UMR 5110, F-66860 Perpignan, France d University of Delaware, Graduate College of Earth, Ocean, and Environment Robinson Hall Newark, DE 19716, USA article info Article history: Received 23 August 2012 Received in revised form 8 January 2013 Accepted 14 January 2013 Available online 31 January 2013 Keywords: Live (stained) benthic foraminifera Ecology Inactive canyon Organic matter Oxygenation abstract Living (Rose Bengal stained) benthic foraminiferal faunas were investigated at 13 deep-sea stations sampled in the Cap-Ferret Canyon area (NE Atlantic). One station (151 m) is located on the continental shelf close to the canyon head. All other stations are located along 2 bathymetric transects: 7 sites along the canyon axis with depths ranging from 300 to 3000 m and 5 stations along the adjacent flank with depths ranging from 300 m to 2000 m. Sedimentological analyses indicate that the Cap-Ferret Canyon is at present inactive in terms of sediment gravity flow. Compared to stations on the adjacent flank, canyon-axis stations are generally characterised by shallow oxygen penetration depths, high diffusive oxygen uptakes (DOU) and high lipid contents. Higher mineralisation rates recorded in the canyon axis are likely due to a preferential focusing of labile organic matter in the canyon axis. Foraminiferal standing stocks do not exhibit any straightforward correlation with the different descriptors of organic matter available in the sediment. However, foraminiferal standing stock and diversity along the canyon axis are generally higher than on the adjacent flank. Canyon axis sites yield dominant species that are similar to those at adjacent flank and open slope stations located at comparable water depths. However, intermediate and deep infaunal species were only recorded in the lower canyon axis, where high amounts of organic matter were observed in deeper sediment layers. Finally, the faunal composition in the Cap-Ferret Canyon is different compared to the nearby Cap-Breton Canyon, where sediment gravity flows are active. The absence of pioneer species and the occurrence of highly specialized taxa are both consistent with the much more stable conditions in terms of hydro-sedi- mentary conditions prevailing in the Cap-Ferret Canyon. & 2013 Elsevier Ltd. All rights reserved. 1. Introduction Submarine canyons are considered to be important conduits for the transfer of inorganic and organic matter from the shelf to deep ocean (Durrieu de Madron, 1994; Canals et al., 2006; Palanques et al., 2006). They are complex environments where the organic matter focusing and the sedimentary dynamics lead to uncommon ecological conditions compared to open-slope settings. Active submarine canyons (as opposed to inactive sub- marine canyons) are characterised by intensive sediment trans- port in the canyon axis. This transport is caused by different, rather unpredictable hydrodynamic processes such as sediment gravity flows (i.e., turbidity currents) (e.g. Cap-Breton Canyon, Mulder et al., 2001), slumps (Kaoping Canyon, Hsu et al., 2008) or shelf water cascading events (Bourcart Canyon, Gaudin et al., 2006). Submarine canyons, where such events occur frequently, are characterised by a high degree of sediment instability, leading to the dominance of highly opportunistic benthic foraminifera thriving at the sea floor (e.g. Koho et al., 2007; Hess and Jorissen, 2009). For instance, in December 1999, a violent storm that affected the Atlantic coast of southern France generated a turbi- dite deposit in the Cap-Breton Canyon (Bay of Biscay, NE Atlantic) (Mulder et al., 2001). The recolonisation of the sediment by foraminiferal fauna was studied by Hess et al. (2005) and Hess and Jorissen, (2009). Four months after this sedimentary event, the living foraminiferal fauna was almost entirely composed of Technitella melo, a taxon which is usually very rare in the Cap-Breton Canyon. This species was the earliest recoloniser after Contents lists available at SciVerse ScienceDirect journal homepage: www.elsevier.com/locate/dsri Deep-Sea Research I 0967-0637/$ - see front matter & 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.dsr.2013.01.004 n Corresponding author. Tel.: þ33241735371; fax: þ33241735352. E-mail address: pauline.duros@gmail.com (P. Duros). Deep-Sea Research I 74 (2013) 98–114