Biogeochemistry of lipid biomarkers and pigments in particulate matter from the frontal structure of the Alboran Sea (SW Mediterranean Sea)
Abstract
The distribution of pigments, and the molecular and isotopic carbon ratios of lipid biomarkers (sterol, fatty alcohol and fatty acids) were used to investigate the different sources and transformation processes of organic matter in the water column of the Almeria-Oran frontal zone. Four sites representative of three different hydrodynamic structures (Mediterranean water, geostrophic Atlantic jet and anticyclonic gyre) were investigated using samples from sediment traps deployed at 100 and 300 m depth and from filtered (0.7 µm) water obtained at depths between 20 to 300 m. In contrast to the relatively fresh sinking particles with elevated concentrations of phyto- and zooplanktonic sterols, suspended particles were extensively degraded with increasing depth and exhibited more terrestrial, bacterial and zooplanktonic character with depth. Whereas diatom-biomarkers predominated in the frontal zone, and in particular in the gyre downstream, flagellate-biomarkers were mainly associated with the suspended particles of the Mediterranean site and gyre upstream of the Atlantic water. Sterol and alcohol biomarkers distributions and 13C values from the jet core and the gyre of Atlantic waters showed a decoupling between the sinking particles of 100 m and 300 m depth, demonstrating the influence of lateral advection in the frontal zone. In contrast, vertical transport of the particulate organic matter in Mediterranean waters was indicated by similar isotopic and molecular composition at both depths. A downwelling of biomass below the euphotic zone on the gyre downstream, due to the effects of the internal secondary circulation, was also observed from the high abundance of phytoplanktonic biomarkers at 100 m depth.
- Publication:
-
EGS - AGU - EUG Joint Assembly
- Pub Date:
- April 2003
- Bibcode:
- 2003EAEJA.....1945T