Particles are introduced into the ocean by biological production, rivers, glaciers, wind and resuspension. Biological, chemical and gravitational influences then act to remove particles from the water column. These removal processes, however, occur on much shorter time scales than the formation, movement or mixing of oceanic water masses. Particles, therefore, do not act as conservative tracers of a particular water mass. However, their presence and concentration indicate the location and intensity of oceanic biogeochemical processes.