This feels like flamebait, but what the hell. I don't think you'll find many people concerned about harassment of marine life by photographers who also engage in (or endorse) spearfishing for sport, or believe catch-and-release gear fishing does no harm to the fish, or much enjoy shooting terrestrial animals for fun.
There's no question (in my mind anyway) that some fish species can become habituated to the presence of non-spearfishing divers - at least to the extent that they can learn that these clumsy large creatures present no obvious threat and can be ignored. That doesn't mean that handling, touching, moving and other forms of harassment aren't stressful and potentially damaging to the animal. It's also reasonable to assume that some species are more sensitive and/or vulnerable than others, but we don't, of course, know which ones or what the real limits are. And even the presence of divers can be a problem. With the possible exception of Blue Corner in Palau, I can't think of many heavily-dived sites that once (say, as recently as 1990) had lots of sharks that still do. That may be mainly because of overfishing, but it's also true that sharks are rare at some sites that are heavily dived but never fished in regions where there are still sharks.
Will a slight touch of the hand kill an entire coral colony? I frankly don't know, but neither does acropora. Again, the true answer might not be simple. There are many coral species, some are probably more vulnerable than others, and it's also reasonable to think that particular corals already stressed by other environmental factors (predation, temperature change) or other divers might be more vulnerable. The theory that even a touch could seriously damage a coral colony is apparently based on the idea that removing or damaging the mucus coating on the surface of a coral colony even in a small area can create an entrypoint for infection and/or make the coral more vulnerability to predators. I don't know if this is really proven, but I'm fairly certain that it hasn't been disproven either.
Whether a slight touch can kill a coral or not, there's no doubt that clumsy fin kicks can do serious damage. Anyone who has ever dived on a truly pristine reef that is rarely or never dived or fished before knows very well the difference between that kind of place and a heavily dived, beaten up sites. One doesn't have to have been diving long to see the deterioration over time in any location that is heavily dived, though it is equally true that heavily dived sites that are protected from fishing (especially destructive fishing practices) may do better over time than undived sites unprotected from fishing pressures.
The bottom line is that corals are live animals, not inanimate rocks. Some of us would view someone who idly carves his/her initials in the bark of a tree (even if the tree is simply "wild", not a threatened species, not located in a national park or nature preserve, and in spite of the well-known fact that many trees have survived this kind of abuse... as I was saying, some of would view that person as .. well, an asshole.
I know I'm hardly pure on this subject. I eat (some) seafood, though I try to stick to tuna and other pelagics taken in fisheries where they are not believed to be under threat. Like Mike V., I examine sea cucumbers for commensals, and crinoids too. On more than one occasion I have accidentally damaged a crinoid I was looking at, and I'd be lying if I claimed I've never damaged a coral. I know very well that I have.
Only a few days ago, I was urging someone on this board to pick up the next Linckia sp. sea star that he saw to look for the lovely parasitic crinoid, Thyca crystallina, that often lives on board. I personally don't believe picking up a Linkia, taking a picture of its parasites, and then replacing it on the same or similar substrate (of course) is likely to harm it - unlike feeding it to a Harlequin shrimp, which I admit I've also done, but I could be wrong. I personally don't believe its ethical to move a photographic subject to a different location for a shot, but I'll admit using a metal rod to gently induce a frogfish and similar creatures to move a couple of inches, and I've stuck the same rod into the sand under a mimic octopus in order to discourage it from re-entering its hole while I was trying to take its picture.
Some might call it sophistry (and they may be right), but there is an important difference between trying (at least) to minimize one's impact as a diver and u/w photographer (with no illusions about that impact ever being zero) and acroporas argument which, if I understand hiim correctly, is that because some people fish, hunt, torture or kill fish and other wildlife for entertainment, and because not everyone condemns this, it's ok to do whatever you want. Or that because commercial fishermen kill snappers, harassing a puffer to induce it to blow up for a photo is also ok. It really isn't. (We know that this treatment seriously stresses the animal, may make it much more vulnerable to other predators, and some puffers subjected to this treatment end up inadvertently swallowing air at the surface which they cannot get rid of and die.
I think Acropora has set up and is arguing with a strawman. Those who object to harassing and possibly killing pufferfishes just for a picture are not the same people who think it's fine to spearfish for fun.
Frogfish
