H. Etcheber et al., Distribution and quality of sedimentary organic matter on the Aquitanian margin (Bay of Biscay), DEEP-SEA II, 46(10), 1999, pp. 2249-2288
Citations number
109
Categorie Soggetti
Aquatic Sciences","Earth Sciences
Journal title
DEEP-SEA RESEARCH PART II-TOPICAL STUDIES IN OCEANOGRAPHY
During the ECOFER experiment (French ECOMARGE program), surficial sediments
were sampled on the Aquitanian margin with box corers and analyzed to dete
rmine the quantity and quality of organic matter. Sediments from the margin
are enriched in organic carbon (mean value 1.35%) in comparison to deep-se
a and shelf sediments, due to a fine grain-size sedimentation. As sedimenta
tion rates are high, the margin appears to be an organic depocenter. Some p
referential organic enrichment zones were identified in the Cap-Ferret Cany
on. There is a supply of continental material from the Gironde estuary, but
marine contribution seems more possible than Adour or spanish rivers. No s
easonal variations of organic matter were observed at the surface of sedime
nts, suggesting mineralization processes of labile organic matter: average
organic carbon consumption was evaluated to 9.0 g C m-(2) yr(-1). Rapid bio
logical mineralization processes are lower than on the Mediterranean margin
, mainly related to significant differences in water temperature. The great
width of the canyon, its distance from the continent, and the current circ
ulation pattern prevent any precise recording of the variable organic input
s to the sediment and favor nepheloid transport, resuspension and shelf bre
ak processes, which wipe out any print of fresh material input. An organic
carbon budget indicates that an equilibrium between organic inputs and orga
nic mineralization + accumulation is not obtainable. The supply of suspende
d matter could have been minor during the year in question, and sedimentati
on rates are still imprecise. (C) 1999 Elsevier Science Ltd. All rights res
erved.