Wikipedia about: Diel playing
During World War II the U.S. Navy was taking sonar readings of the ocean when they discovered the deep scattering layer (DSL). The DSL was caused by large groupings of organisms that scattered the sonar to create a false or second bottom. The false bottom was shallower during the night and deeper during the day; this was the first recording of diel vertical migration.
Once scientists started to do more research on what was causing the DSL, it was discovered that a large range of organisms were vertically migrating. Most types of plankton and some types of nekton have exhibited some type of vertical migration, although it is not always diel. These migrations may have substantial effects on and apex predators by modulating the concentration and accessibility of their prey (i.e. impacts on the foraging behavior of pinnipeds).
Types and stimuli of vertical migration
There are two different factors that are known to play a role in vertical migration, endogenous and exogenous. Endogenous factors originate from the organism itself; sex, age, biological rhythms, etc. Exogenous factors are environmental factors acting on the organism such as light, gravity, oxygen, temperature, predator-prey interactions, etc.
- Endogenous rhythm- An experiment was done at the Scripps Oceanographic Research Institute which kept organisms in column tanks with light/dark cycles. A few days later the light was changed to a constant low light and the organisms still displayed