bleached reef will recover, provided the necessary improvement but might not be 100%.
global warming is the primary cause and overfishing being the one of the least secondary. the next big thing is water pollution.
if you are talking about less poo, take at look at the sewage to the sea, it contain more nutrients that keep phyptoplankton, algae and red slime cyno extremely happy.
of course, not all reef are experience the pollution directly, but water and water are side by side.
In short, temperature plays a biggest role in the reef, if the water is too warm, zooxanthellae being expelled, coral bleached and stony corals got problem building their skeleton. they need a specific certain temperature to do so. too warm? nono