Recently I snorkeled some coral reefs off the coast of the Yucatan peninsula in Mexico and was surprised to be informed that I should not be using sunblock while doing so. Obviously coral reef preservation is an important concern and I had read that a changing climate is altering the symbiosis in coral reefs and has resulted in coral bleaching, however I was completely unaware that sunscreen (ie blocking my vitamin D production) had an environmental impact. Seriously disappointingly I can't find anything on the internet about sunscreen effects on coral reefs other than claims specifically made by diving/snorkeling sites off the coast of the Yucatan. Also the majority of information on biodegradable sunscreen is from tourist directed websites and forums about Cancun and the Yucatan peninsula. Certainly with something as apparently delicate as coral reefs it is probably best to be cautious but where is the science on this issue? Sounds like a great research project full of sun and snorkeling. Interestingly there is some research on deriving sunscreens from compounds found in coral reefs.
I'm definitely waiting on Melanotan. However because of it's biological activity it might be even more harmful to reef life.