Bottom and Intermediate nepheloid layers
In the deep ocean, the depth profile of suspended particles (SPM), mostly measured as beam attenuation, usually shows a minimum at mid-depth. Below this clear water minimum, SPM load gradually increases and often a dramatic increase is observed close to the seafloor, the benthic nepheloid layer (BNL). In the deep water and especially in this BNL, particles can be transported over very large distances. Thus, the BNL is affected by horizontal advection, fresh new particle rain and exchange with the surface sediment by the resuspension-settling cycle. Reversible particle-water exchange (scavenging and release) and grain size sorting will continue to adjust the distribution of trace elements and their isotopic composition over the particulate and dissolved phases. We want to discuss how this interaction between vertical and horizontal transports affects the tracer signals recorded in the surface sediments.