They house bacteria within them, living in apparently inseparable symbiosis. The worm has no gut, no mouth, no anus. Thus, the scientists who first saw it assumed that it simply absorbed nutrients from the water. Trophosome bacteria flourish because they are supplied with large quantities of hydrogen sulfide delivered through the worm's bloodstream. Worms, which apparently produce a special blood protein to detoxify hydrogen sulfide, survive by absorbing nutrients from the bacteria.
Vent creatures grow at a frantic rate, probably producing large numbers of offspring in larval form.
When a vent closes, hardy larval scouts can drift long distances, a few making it to other vents and beginning their community anew. But few Oasis scientists seemed worried. The vent system is too vast. I'd say this is an area where we don't have to worry about man's activities much. Others believe vent creatures might even be hardy enough to colonize vapory Venus and other alien worlds.