Beschreibung: A vertical flux pulse related to spring phytoplankton development was recorded ·by moored sediment traps at 42°N 06°E in the Gulf of Lions. May 1990 trap samples from 200m to 2000m depth were comprised of freshly produced organic matter and selected microplankton species from the overlaying water column. This vertical flux event was transmitted to the deep sea floor with a high particle sinking velocity of 〉140 m day-1. Maximal vertical fluxes of 35 mg C m-2 day-1 and 1.2 mg chl.a m-2 day-1 recorded during this event are low compared to the exports from collapsing spring blooms at higher latitudes but demonstrate that particle production and degradation within the spring pelagic system were not in balance.

Beschreibung: Rare earth element (REE) composition of sinking particles was examined in time-series sediment trap samples collected from four depths (200, 500, 1000, 2000 m) in the Gulf of Lions. Vertical flux profiles showed the occurrence of a sedimentation pulse which resulted in the rapid sinking of phytoplankton aggregates to 2000 m depth. These particles were characterized by REE patterns similar to those in the upper 200 m indicating that little, if any, additional REE scavenging occurred during the sedimentation event. In contrast, after the sedimentation pulse, particles from deep waters showed an enrichment of light-REE (LREE) relative to heavy-REE (HREE) and a positive Ce anomaly. Comparing REE patterns in particles from the upper water column (200 m) with those from depth (1000, 2000 m) during and following the sedimentation pulse indicates that time is a key factor in determining REE scavenging by sinking particles. This is particularly evident for the preferential scavenging of Ce (IV) which is most pronounced in the finer, slowly sinking, and presumably older particles. These findings are consistent with REE patterns in sea water from the northwestern Mediterranean which show a strong negative Ce anomaly and gradual enrichment of REE with increasing atomic number. The enrichment of LREE relative to HREE in particles from deep waters results either preferential scavenging of LREE on particles, analogous to the enrichment of Ce, or selective dissolution of HREE in association with particle remineralization processes, or both; this aspect of REE behaviour merits further study.