Alex Mustard - Convict Tangs
Although coral reefs are famous for their corals, there is also tremendous growth of seaweeds there too. So why aren’t reefs green and covered in seaweeds? Well we don’t see large seaweeds when we dive on a reef because they are eaten almost as quickly as they can grow by the herbivores. More than 50% of the weight of fish on a reef can be herbivores and their grazing is ferocious. Herbivorous fish can make as many as 40000 to 15000 bites on a square meter of reef each day.
If we were to place a cage over part of the reef, to keep out the herbivores, the seaweeds would soon grow up and any corals in the cage would die back. Herbivores, like this gang of convict tangs, clearly play a crucial role in maintaining the delicate balance between coral and seaweeds on the reef.