Coral Reefs on a Changing Planet
A coral reef is like an underwater city. Corals and algae construct the framework that rises off the tropical ocean floor and attract many diverse inhabitants. Schools of multicolored fish glide above the structure. Invertebrates dart around on its surface. All that busy activity and all that life exists in a delicate balance.
This delicate balance is threatened by humans in many ways. Some of the threats are easy to see - plastic bottles and other trash littering reefs, sediment in the water or settling on the reef corals, and water pollution. Overfishing is reducing the number of grazing fish in some areas. And scratches on corals from the fins of careless snorkelers, anchors, or even deep gouges from boats that have run aground are visible in many reefs.
There are also threats that are less visible yet pose great dangers to coral reefs like acidic seawater, warmer seawater, and coral diseases. The threats might be hard to see, but their effects are not. Some reefs have been so hard hit that scientists say they will not be able to recover. Scientists predict that over half of the world’s coral reefs may die by 2050 if these threats continue.
Acid Seawater: More of the greenhouse gas carbon dioxide means more global warming, but also, some of it gets into the oceans. Carbon dioxide makes seawater more acidic. And acidic water makes it difficult for coral and algae to build the reef.
Warmer Seawater: As the Earth warms, so do its oceans. When seawater gets too warm, corals release the algae that live within their tissues – a process called coral bleaching. Some reefs might be protected if there are areas of the ocean that are able to stay cool.
Coral Diseases: These diseases are caused by bacteria, fungi, and viruses. There are more diseased corals today than there were several decades ago. These diseases do occur naturally but are also brought on by pollution and other changes to the environment.