Evidence of bioturbation in the Cap-Ferret Canyon in the deep northeastern Atlantic |
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| Institution: | 1. Centre d''Océanologie de Marseille, Laboratoire d''Océanographie et de Biogéochimie, UMR 6535, Campus de Luminy, Case 901, 13288 Marseille Cedex 09, France;2. Département de Géologie et Océanographie, URA CNRS 197, Av. des Facultés, 33405 Talence, France;1. A.V. Zhirmunsky Institute of Marine Biology, National Scientific Center of Marine Biology, Far Eastern Branch, Russian Academy of Sciences, 17 Palchevskogo St, Vladivostok 690041, Russia;2. Far Eastern Federal University, Ajax St., Russky Island, Vladivostok 690600, Russia;1. Graduate School of Fisheries Sciences, Hokkaido University, 3–1–1 Minatomachi, Hakodate, Hokkaido 041–8611, Japan;2. Marine Bioscience, Kitasato University, 1–15–1, Kitasato, Minami, Sagamihara, Kanagawa 252–0373, Japan;3. Atmosphere and Ocean Research Institute, The University of Tokyo, 5–1–5, Kashiwanoha, Kashiwa–shi, Chiba 277–8564, Japan;4. National Institute of Polar Research, 10–3, Midoricho, Tachikawa, Tokyo 190–8518, Japan;5. Graduate School of Frontier Sciences, The University of Tokyo, 5–1–5 Kashiwanoha, Kashiwa, Chiba 277–8564, Japan |
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| Abstract: | In the sedimentary column, a combined quantification of burrows and macrobenthic community provides evidence of bioturbation features in the submarine canyon of Cap-Ferret between 2000 and 3000 m depth. An image-processing technique allows accurate quantification of burrow volumes with depth in the sedimentary column. The major bioturbation mode seems to be different in the channel compared to the interfluve. Macrobenthic activity is more inclined to mix the sediment in the channel in response to increased organic matter supplies. Sediment mixing leads to burrow destruction in the upper mixed layer of sediment in the canyon. Burrows are better preserved on the interfluve where mixing is slower. Under the mixed zone, the volume of recorded burrows is higher when sedimentation rate increases, as in the upper canyon. In this transition layer, the burrow volume is estimated to be between 3 and 64% of the total sediment volume depending on the sediment depth. The fill-down of numerous burrows with surface sediment by bioregeneration suggests that anaerobic degradation of fresh organic matter is dominant in this canyon. In the sedimentary column, the negative relationship between carbonate content and macrobenthic abundance confirms that carbonate dissolution is largely influenced by bioturbation. |
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