The Issue that is... Extinction
Tiger Shark- If the tiger shark was driven to extinction then the number of moray eels would increase because this is the tiger shark's prey. The dugong and turtle numbers would increase, but only slightly as the saltwater crocodile also eats these species. The Parrotfish numbers would decrease because there are more moray eels and the eels eat the parrotfish.
Dugong- If the dugong became extinct there would be less competition for the seagrass and turtle numbers would initially increase, however there would be less food for the crocodile and tiger shark so they would eat more turtles , parrot fish and moray eels. The shark numbers would stabilise however the crocodile and turtle numbers would go down as crocodiles now have only one species to eat and that is the turtle. Parrotfish and Moray eel numbers would also go down as these are preyed upon by sharks. Butterfly fish numbers would increase as the number of the predator which eats them, moray eels, goes down and this may also affect the types of corals that these butterfly fish eat.
Seagrass- If seagrasses were extinct in the Great Barrier Reef, then the dugong and turtle numbers would decrease as they eat the seagrass, and the number of prawn would also decrease because they live in these seagrasses. This would cause a collapse of the crocodile and shark population, though sharks could switch their diet to more parrotfish and moray eels therefore affecting their populations as well.
Dugong- If the dugong became extinct there would be less competition for the seagrass and turtle numbers would initially increase, however there would be less food for the crocodile and tiger shark so they would eat more turtles , parrot fish and moray eels. The shark numbers would stabilise however the crocodile and turtle numbers would go down as crocodiles now have only one species to eat and that is the turtle. Parrotfish and Moray eel numbers would also go down as these are preyed upon by sharks. Butterfly fish numbers would increase as the number of the predator which eats them, moray eels, goes down and this may also affect the types of corals that these butterfly fish eat.
Seagrass- If seagrasses were extinct in the Great Barrier Reef, then the dugong and turtle numbers would decrease as they eat the seagrass, and the number of prawn would also decrease because they live in these seagrasses. This would cause a collapse of the crocodile and shark population, though sharks could switch their diet to more parrotfish and moray eels therefore affecting their populations as well.