A new study by the Australian Research Council says that more than 40% of the reef is covered in seaweed. One professor thinks that the increase in seaweed could mean that there are not enough grazing fish to eat it, or something more serious. More studies are now under way to try and work out what is happening and if climate change could be part of the cause.

Not everyone agrees with the study, though. Some people who operate scuba diving companies in the area think that the scientists are only studying a small area of the reef, instead of looking at the entire 2,500km.