Inexperienced divers damage coral, but parrot fish eating coral doesn't do damage?

Question

I've been learning about life on coral reefs. Recently I've become aware of the damage to coral reefs caused by tourism and inexperienced divers: 1) Corals have a thin membrane which keeps them healthy. Touching them could break this membrane, causing infection which can lead to death. 2) Stepping on, leaning on, and sitting on coral could smash their polyps. I am not against being responsible as a diver, respecting nature, arriving and leaving without a trace. I'm just curious what the difference is between human and animal contact. Parrot fish eat coral, taking bites out of it, leaving exposed areas and this damages the coral. I've seen footage of sharks having feeding frenzies on reefs, where they smash into the reef during the commotion and while trying to catch their prey. Fish rub up against coral and peck at them to get algae, and crustaceans walk on the coral with legs that seems like it would break the thin protective membrane on the coral. Obviously, as humans we technically do not belong in their world, so I'm sure there are reasons for damage with that alone; but why does marine life causing damage not cause actual damage? Or does it, and it just repairs differently or faster somehow?

Answer 1

I think that marine life does cause damage to coral as they travel across it and feed on it, the difference may be the perception that humans are trying to leave a little of an impact on nature as possible when diving near or touring coral reefs. Divers want to observe the coral and study it without documenting the impact of humans, just as nature film crews are told to not interfere with the animals they observe (for instance saving a wounded animal from a predator because that would upset the balance and natural order of nature). On the other hand, tourism can have a much larger impact on the coral than the natural marine life normally would. Parrot fish take bites across the entire coral reel but do not always decimate it, allowing it to recover and regrow. Shark frenzies can destroy a coral reef but it is not guaranteed, it just depends on if they happen to be close enough to the reef. And crustaceans can damage the reef while they travel across it but they are not trampling it. All of this seems minimal compared to numerous people poking, prodding, and stepping on the coral reefs every day. There are some tourism businesses dedicated to drawing crowds in and taking them out to explore the coral reefs, so the amount of human damage accumulates very quickly compared to the damage from marine life.