Another key process occurring in this zone is the diel vertical migration of certain species, which move between the euphotic zone and mesopelagic zone and actively transport particulate organic matter to the deep. In one study in the Equatorial Pacific, myctophids in the mesopelagic zone were estimated to actively transport 15-28% of the passive POC sinking to the deep, while a study near the Canary Islands estimated 53% of vertical carbon flux was due to active transport from a combination of zooplankton and micronekton. When primary productivity is high, the contribution of active transport by vertical migration has been estimated to be comparable to sinking particle export.