Relation between 234Th scavenging and zooplankton biomass in Mediterranean surface waters

Dissolved and particulate 234Th activities were determined and phyto-and zooplankton biomass were periodically measured 8 miles off Nice (Mediterranean Sea) during spring 1987. The results show a strong variability of 234Th distribution on short time scales in northwestern Mediterranean surface waters. The good correlation observed the zooplankton biomass and the rate of 234Th export to deep water in particulate form is agreement with the assumption that the residence time of particulate 234Th in oceanic surface waters is controlled by zooplankton grazing. Moreover, our results indicate the importance of salps in particular as efficient removers of small suspended particles in surface waters