What are the biggest perceived threats to the reef?

Islands in the whitsundays

The Great Barrier Reef Marine Park maintains a fine balance in order to stay healthy and thriving, just like most ecosystems! It relies on the weather, water temperature, tides and overall water health in order to remain healthy itself. Any small interruption in its equilibrium can result in changes in habitat.

The two biggest perceived threats to the Great Barrier Reef Marine Park today are coral bleaching and the crown-of-thorns starfish. Both have major effect on the reef, with the long term effects largely unknown as research is still ongoing.

Coral bleaching

Coral bleaching is one of the biggest ongoing threats to the marine park. This is an issue that can affect all reefs, anywhere in the world, as it is caused when the relationship between coral and symbiotic algae is disrupted. When coral becomes stressed due to pollution, heat or other changes in the environment, it may expel its algae, which in turn, causes the coral to have a bleached look. The algae is what gives the coral not only its colour, but also its nutrients. Today we may see corals like this in the Great Barrier Reef Marine Park, predominately in the North. This is due to the fact that is often a result of rising temperatures, which is more drastic in the north of Australia. Despite common belief, a bleached coral is not always a dead one. If algae leaves the coral, it may go on surviving until the threat passes, when the algae may move back in and resume normal life. However, if left too long, the coral can starve to death and die. There are currently many surveys going on in the Great Barrier Reef Marine Park to analyze the extent of the damages from the last major bleaching event, which began in 2016. It is unknown how this will affect the reef overall and what impact it will have on its future at this stage.

Crown-of-thorns starfish

The crown-of-thorns starfish is a current plight to many individual reefs in the Great Barrier Reef Marine Park. The invasive species, while damaging, is a native to the Great Barrier Reef Marine Park and is always found all over the reef. However, in recent years, there has been a rise in its numbers due to unknown reasons. The crown-of-thorns feeds on corals, attacking particularly the staghorn, which are a fast growing coral. They consume large quantities, leaving a trail of bleaching coral skeletons behind as they eat their prey. There have been preventative measures taken to destroy as many of the crown-of-thorns as possible to give the other corals a chance to thrive and survive, but humans can only do so much when you are dealing with the vast scale of space in the marine park. While this is current common practice, the extent of the damage done by the crown-of-thorns is unknown. It is entirely possible that the increase in their numbers is a natural phenomenon that helps to promote health on the reef. One theory is that by removing the fast growing corals, the crown-of-thorns is clearing up free real estate for new coral species to move in and regenerate and that it is a natural process that happens on the Great Barrier Reef. Other theories in their increase include runoff from farming which have allowed them to multiply at unnatural levels, or that high levels of fishing and fishing exploitation have decreased the number of animals that prey on their larvae, allowing many more to survive to adulthood.

Both situations are being monitored by the Great Barrier Reef Marine Park Authority. If you have anything to report, such as crown-of-thorns outbreaks, you can report them to www.gbrmpa.gov.au.

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