The significance of frontal processes for vertical particle fluxes: A case study in the Alboran Sea (SW Mediterranean Sea)

Abstract

Vertical particle fluxes were measured in the eastern Alboran Sea (SW Mediterranean Sea) in waters of Atlantic and Mediterranean origin and in the geostrophic frontal jet in between. At different locations relative to the frontal jet drifting sediment traps were deployed at depths of 100 m and 300 m for 1–1.5 d and suspended matter was monitored simultaneously. In contrast to the oligotrophic Atlantic and Mediterranean waters, a high phytoplankton biomass (max. 97 mg chl. a m −2) was observed in the frontal region; this comprised a prominent diatom component as shown by analyses of biogenic particulate silica and microscopical observations. Vertical particle fluxes in the frontal region were up to 10 to 100 times higher than in the Atlantic and Mediterranean waters and were dominated by components with au autotrophic origin (maxima 45 mg POC m −2 d −1, 1 mg chl. a m −2 d −1 and 20 mg particulate silica m −2 d −1). Results demonstrate that the specific hydrographic and biologic properties of the frontal region are prominently reflected in vertical particulate fluxes from the euphotic zone. Water column and trap data suggest that cross-frontal isopycnal transport had an impact on the distribution of suspended and sedimenting particles.