Why are these organisms by the deep sea vents?
It really depends on the type of cell and the replacement rate. Mitosis or cell division occurs in places where the cells get damaged easily. For example, skin cells frequently divide and undergo mitosis because they are replaced very often. On the contrary, heart cells never get replaced and actually never really undergo mitosis (there is no need for it)
Since the Ribosomes are often referred to as the "powerhouse" of a cell, the cell would basically shut down. And also the Ribosomes are the place where the proteins for a cell are made, so if the Ribosomes shut down, the cell won't have any proteins or energy to do all its processes.
An arc flash can occur when differences of potential voltage reading exists. An arc flash an enormous amount of radiant energy that explodes outwards from electrical equipment, creating pressure waves These high intensity pressure waves can damage a person's hearing or even eyesight.