Fluorescence and DOC contents of pore waters from coastal and deep-sea sediments in the Gulf of Biscay

Fluorescence of waters from the Gulf of Biscay was investigated. Pore water s fluoresced more intensely and exhibited red-shifted spectra relative to o verlying seawaters. Also, a blue-shift was observed going from coastal to o pen sea sites. Results indicate that continental inputs of fluorescent mate rial reach the sea bed at all sites studied. Organic matter (OM) modificati ons within sediments were also observed. In the uppermost layer (6 cm), flu orescence intensity and dissolved organic carbon (DOC) concentrations decre ase, followed by a red-shift in emission spectra with increasing depth. Thi s may reflect the increase in OM molar mass due to humification. The revers e of these trends in the deepest sub-oxic sediments might be related to the degradation of OM released from the solid phase, resulting in dissolved fl uorescent material with a relative paucity of oxygen-containing functional groups, A very good correlation of DOC with fluorescence was observed in al l cores. (C) 2001 Elsevier Science Ltd. All rights reserved.