Why do populations in the deep sea tend to have longer life spans than those in the higher layers?

The one of the marine creature named Mediterranean red coral lifespan is capable of covering nearly 500 years and challenge human age with full spirit, also observed that the patterns of sessile or immobile species like other corals, macroalgae, sponges and gorgonians have boon of long life under deep sea water.

One of the most basic reason behind their healthy life is the stability of environment which is favorable for deep-dwelling species, they get shielded from temperature changes and severe storms in such location. Pollution, poaching, contamination, human activities, etc are not that effective in deep sea, natural selection favors long lifespans in stable environments.