A comparison of aggregate profiles with sediment trap fluxes

Abstract

Previous work (by us and other) has shown that sediment trap fluxes do not correlate well with the total particulate mass concentration as determined with a transmissometer. Sediment traps are thought to collect the setting particles in the marine snow size range (d 〉 0.5mm). Cameras have been developed to quantitatively image particles in the marine snow size range but a correlation between measured flux in sediment traps and large-particle camera (LPC) profiles has not been established. In this study, LPC total particulate volume data are correlated with fluxes measured in sediment traps, indicating that sediment traps sample the large aggregate size range and that the flux is proportional to the concentration and size distribution of large aggregates. Partitioning of the major components of the bulk chemistry indicates that rebound aggregates (particles which do not undergo an appreciable change in their bulk chemistry before resuspension from the seafloor) contribute to aggregate nepheloid layers and increase measured trap fluxes. The bulk chemical composition of material from the deepest sediment traps indicates that downslope advection as well as cross-slope advection and subsequent settling may be amportant pathways for biogenic material to the deep ocean.