Humans greatly impact coral reefs in many different ways. These can include oil spillage, garbage dumping, and pesticides.
Oil spills massively contribute to marine pollution, with even the smallest of leaks causing serious damage in sensitive areas and killing wildlife.
Garbage dumping can damage the environment by killing plants by not allowing them to get enough sunlight, or taking many years to biodegrade, and, in turn, suffocating them. Heavy objects can also directly damage the environment, by crushing or breaking coral, rocks or any other marine structures. Garbage dumping can also kill marine animals, as they may attempt to ingest garbage, and choke in the process.
Pesticides can pollute water and kill marine wildlife. The pesticides run off crops during rain, and usually into a body of water, where it could potentially enter the ocean. When the pesticide has entered the ocean, it then pollutes the water, and can then harm marine wildlife. The wildlife is poisoned by ingesting the pesticides, resulting in them being poisoned by it and eventually dying.
Ocean acidification is the process in which carbon dioxide dissolves from the atmosphere to create carbonic acid, which decreases the pH levels of the ocean. This causes corals to become more brittle, and doesn't allow them to form or start new corals.
Temperature changes brought on by climate change can stress corals out. If the water temperatures stay at a higher temperature than usual for several weeks, the zooxanthellae they depend on for most food leave their tissue, which drains the colour from the corals, as the zooxanthellae are what give coral their colour.
If a resort were to be developed on Heron Island, it would greatly impact the ecosystem. Many turtles live and give birth on Heron Island's beaches, so if a resort was built on the turtles' breeding grounds, there turtles would have nowhere to lay eggs. Several species of birds, such as silver gulls and mutton birds also reside on the island, so building a resort could destroy or at least threaten the homes of these birds. It could also affect the coral reefs surrounding the island, by disturbing the wildlife and, potentially, physically damage the reefs by breaking off bits of the reef. After the resort is constructed, it could continue to damage the marine wildlife surrounding the area through disposing sewage, and boat traffic damaging the reefs.