The Great Barrier Reef has more different types of species than any other environment. It is a breeding area for humpback whales, as well as six different species of turtles. Below is a food web that shows the relationship between the animals.
Sharks are the main predators in the Great Barrier Reef. They prey on fish, and the fish prey on primary producers such as algae, sea grass, and sponge. There is also a parasite called a trematode, that is found in almost every fish, bird, and turtle in and near the Great Barrier Reef. There are also herbivorous reef fish that play a beneficial role for the coral by decreasing algae growth and help allow coral to settle and grow.
Information from Australia's Great Barrier Reef Marine Park Authority