FN Archimer Export Format PT J TI Cold-seep-like macrofaunal communities in organic- and sulfide-rich sediments of the Congo deep-sea fan BT AF OLU, Karine DECKER, Carole PASTOR, Lucie CAPRAIS, Jean-Claude KHRIPOUNOFF, Alexis MORINEAUX, Marie AIN BAZIZ, M. MENOT, Lenaick RABOUILLE, C. AS 1:1;2:1;3:1;4:1;5:1;6:1;7:1;8:1;9:2; FF 1:PDG-REM-EEP-LEP;2:PDG-REM-EEP-LEP;3:PDG-REM-EEP-LEP;4:PDG-REM-EEP-LEP;5:PDG-REM-EEP-LEP;6:PDG-REM-EEP-LEP;7:;8:PDG-REM-EEP-LEP;9:; C1 IFREMER, Ctr Bretagne, Lab Environm Profond, BP 70, F-20280 Plouzane, France. Univ Paris Saclay, Lab Sci Climat & Environm, Gif Sur Yvette, France. C2 IFREMER, FRANCE UNIV PARIS SACLAY, FRANCE SI BREST SE PDG-REM-EEP-LEP IN WOS Ifremer jusqu'en 2018 copubli-france copubli-univ-france IF 2.451 TC 22 UR https://archimer.ifremer.fr/doc/00384/49561/50053.pdf LA English DT Article CR CONGOLOBE WACS BO Pourquoi pas ? DE ;Chemosynthesis-based ecosystems;Cold seeps;Organic rich sediments;Macrofaunal communities AB Methane-rich fluids arising from organic matter diagenesis in deep sediment layers sustain chemosynthesis-based ecosystems along continental margins. This type of cold seep develops on pockmarks along the Congo margin, where fluids migrate from deep-buried paleo-channels of the Congo River, acting as reservoirs. Similar ecosystems based on shallow methane production occur in the terminal lobes of the present-day Congo deep-sea fan, which is supplied by huge quantities of primarily terrestrial material carried by turbiditic currents along the 800 km channel, and deposited at depths of up to nearly 5000 m. In this paper, we explore the effect of this carbon enrichment of deep-sea sediments on benthic macrofauna, along the prograding lobes fed by the current active channel, and on older lobes receiving less turbiditic inputs. Macrofaunal communities were sampled using either USNEL cores on the channel levees, or ROV blade cores in the chemosynthesis-based habitats patchily distributed in the active lobe complex. The exceptionally high organic content of the surface sediment in the active lobe complex was correlated with unusual densitiesof macrofauna for this depth, enhanced by a factor 7 to 8, compared with those of the older, abandoned lobe, whose sediment carbon content is still higher than in Angola Basin at same depth. Macrofaunal communities, dominated by cossurid polychaetes and tanaids were also more closely related to those colonizing low-flow cold seeps than those of typical deep-sea sediment. In reduced sediments, microbial mats and vesicomyid bivalve beds displayed macrofaunal community patterns that were similar to their cold-seep counterparts, with high densities, low diversity and dominance of sulfide-tolerant polychaetes and gastropods in the most sulfidic habitats. In addition, diversity was higher in vesicomyid bivalve beds, which appeared to bio-irrigate the upper sediment layers. High beta-diversity is underscored by the variability of geochemical gradients in vesicomyid assemblages, and by the vesicomyid population characteristics that vary in density, size and composition. By modifying the sediment geochemistry differently according to their morphology and physiology, the different vesicomyid species play an important role structuring macrofauna composition and vertical distribution. Dynamics of turbiditic deposits at a longer temporal scale (thousands of years) and their spatial distribution in the lobe area also resulted in high heterogeneity of the “cold-seep-like communities”. Dynamics of chemosynthetic habitats and associated macrofauna in the active lobe area resembled those previously observed at the Regab pockmark along the Congo margin and rapid succession is expected to cope with high physical disturbance by frequent turbiditic events and huge sedimentation rates. Finally, we propose a model of the temporal evolution of these peculiar habitats and communities on longer timescales in response to changes in distributary channels within the lobe complex. PY 2017 PD AUG SO Deep-sea Research Part Ii-topical Studies In Oceanography SN 0967-0645 PU Pergamon-elsevier Science Ltd VL 142 UT 000408783500013 BP 180 EP 196 DI 10.1016/j.dsr2.2017.05.005 ID 49561 ER EF