Silicoflagellates and Actiniscus : vertical fluxes at Pacific and Atlantic sediment trap stations

Abstract

Vertical fluxes of silicoflagellate skeletons were measured in meso- and bathypelagic zones at four P ARFL UX sediment trap stations located in the Pacific and Atlantic oceans. The average flux measured at several depths ranged from 35 X irf skeletonsjm2/day at the Pacific gyre (PI) station to 424 X irf skeletonsjm2/day at the Panama Basin (PBi) station. The skeletal fluxes at these stations constituted a few weight percent or less of the total biogenic opal flux. The fluxes measured at Station Pi, as well as the relative abundance of different assemblages, were fairly constant with depth. At Station PBi, while relative abundance of assemblages was constant with depth, the flux measured at mesopelagic depths was threefold greater than that in the bathypelagic zone. At equatorial Atlantic Station E a slight increase toward the bathypelagic zone is correlated with gradual change in the relative abundance of two predominant taxa, suggesting seasonality in the production of each taxa. Aggregate forms of vertical settling were observed at Station E; the number of skeletons in the aggregates was more than one-half of the total number in the mesopelagic zone and it decreased with increasing depth. The percent abundances of Dictyocha messanensis messanensis and Distephanus pulchra are correlated with organic carbon flux at four stations. Preservation of the skeletons in Holocene sediment at Station PI is less than one percent of the silicoflagellate flux.