Adenosine triphosphate (ATP) is indeed a vital component of living organisms. ATP is an organic chemical that provides energy to the cells of living organisms. Without it, nerve impulses don't propagate, muscles don't contract, and a whole host of other things do not happen.
In answer to the first question, if ATP were to simply cease to exist in the creatures mentioned in the question, then those creatures would no longer be able to generate the light they use for bioluminescence.
A lot of different possibilities exist from this point forward. The bioluminescence is an adaptation that allows those creatures to increase their overall fitness. If the light helps a creature hunt, then their ability to capture prey is seriously hurt without the light. This could actually result in the extinction of the species. If the organism isn't finding food, then it cannot survive long enough to reproduce.
Alternatively, the loss of ATP might cause a rapid evolutionary change within the organisms. This could mean that the organisms quickly develop another way to produce light apart from ATP. It could mean that the creatures figure out an alternative hunting method that works just as well without the bioluminescence. This second possibility might change a particular food chain and related food web, but that assumes the light-producing creature is forced to change the prey. The food web would actually be changed with the creatures going extinct too. Population numbers would increase below the now missing link, but organisms that were higher on the chain would suffer since a food source is now missing from the food web.