Bathypelagic

Diel vertical migration

Some bathypelagic species undergo vertical migration, which differs from the diel vertical migration of mesopelagic species in that it is not driven by sunlight. Instead, the migration of bathypelagic organisms is driven by other factors, most of which remain unknown. Some research suggests the movement of species within the overlying pelagic region could prompt individual bathypelagic species to migrate, such as Sthenoteuthis sp., a species of squid. In this particular example, Sthenoteuthis sp. appears to migrate individually over the course of ~4–5 hours towards the surface and then form into groups. While in most regions migration patterns can be driven by predation, in this particular region, the migration patterns are not believed to result solely from predator-prey relations. Instead, these relations are commensalistic, with the species who remain in the bathypelagic benefitting from the POM mixing caused by the upward movement of another species. In addition, the vertical migrating species' timing bathypelagic appears linked to the lunar cycle. However, the exact indicators causing this timing are still unknown.