CHEMICAL AND METABOLIC INDEXES OF VERTICAL FLUXES IN A GEOSTROPHIC FRONT

Bulk seawater fluorescence and particulate lipid concentrations were m easured at stations localized across the Liguro-Provencal front (NW Me diterranean Sea) during cruises performed in September 1989 and March- April 1990. Mineralization of the organic matter was estimated by dete rmining its oxidation rate by marine microorganisms (ETS assay). Depen ding on the season, the front can be clearly detected by peaks in the horizontal distribution of fluorescent dissolved organic matter, parti culate lipids and ETS activity. Deep maxima characterized the vertical distribution of these parameters in the frontal area and give evidenc e of the importance of organic matter downwelling in the fluxes other than sedimentation. The depth locations of these maxima are discussed and support the hypothesis of a vertical flux of organic matter result ing from an oblique transfer from offshore surface productive zones to deeper waters inshore.