Evidence of bioturbation in the Cap-Ferret Canyon in the deep northeasternAtlantic

In the sedimentary column, a combined quantification of burrows and macrobe nthic community provides evidence of bioturbation features in the submarine canyon of Cap-Ferret between 2000 and 3000 m depth. An image-processing te chnique allows accurate quantification of burrow volumes with depth in the sedimentary column. The major bioturbation mode seems to be different in th e channel compared to the interfluve. Macrobenthic activity is more incline d to mix the sediment in the channel in response to increased organic matte r supplies. Sediment mixing leads to burrow destruction in the upper mixed layer of sediment in the canyon. Burrows are better preserved on the interf luve where mixing is slower. Under the mixed zone, the volume of recorded b urrows is higher when sedimentation rate increases, as in the upper canyon, In this transition layer, the burrow volume is estimated to be between 3 a nd 64% of the total sediment volume depending on the sediment depth. The fi ll-down of numerous burrows with surface sediment by bioregeneration sugges ts that anaerobic degradation of fresh organic matter is dominant in this c anyon. In the sedimentary column, the negative relationship between carbona te content and macrobenthic abundance confirms that carbonate dissolution i s largely influenced by bioturbation. (C) 1999 Published by Elsevier Scienc e Ltd. All rights reserved.