Sharks, which species are rapidly declining across the World, are an excellent barometer for Coral Reef Health as they are the apex predator in a complex food web formed within and around the Coral Reef
If the base of this food web is dwindling/incomplete the Apex Predator is greatly affected. This is why you see many of the pristine, remotely located atoll reef systems have thriving, ever present Shark Populations
Sadly, much of this decline is caused DIRECTLY by **** sapiens. Its not exactly a politically correct statement but in all honesty:
OUR SPECIES IS A VIRUS. One that reproduces rapidly, and at an extent in which all available resources are consumed, with utter disregard to their sustainability, until there is nothing left to consume. The waste/byproducts of this is uncomprehensible ...