Mean particle sinking rates are 10 to 100 m/day. Sinking rates have been measured in the project VERTIGO (Vertical Transport in the Global Ocean) using settling velocity sediment traps. The variability in sinking rates is due to differences in ballast, water temperature, food web structure and the types of phyto and zooplankton in different areas of the ocean. If the material sinks faster, then it gets respired less by bacteria, transporting more carbon from the surface layer to the deep ocean. Larger fecal pellets sink faster due to gravity. More viscous waters could slow the sinking rate of particles.