Record high temperatures in the Pacific Ocean destroying coral reefs
Since 1985, the Great Barrier Reef’s coral has been ravaged by tropical storms, invasive crown-of-thorns starfish, disease, and coral bleaching driven by rising ocean temperatures.
Coral reefs are crucial incubators of the ocean’s ecosystem, providing food and shelter to a quarter of all marine species. The reefs support fish stocks that feed more than a billion people, while an estimated 30 million small-scale fishermen rely on reefs for their livelihoods. Reefs are made up of millions of tiny animals called polyps that form symbiotic relationships with algae, which in turn capture sunlight and carbon dioxide to make sugars that feed the polyps.
Coral bleaching occurs when high heat and bright sunshine cause the metabolism of the algae to speed out of control; algae then starts creating toxins, which in turn leads the polyps to recoil. If temperatures drop, coral can recover, but the denuded ones remain susceptible to disease. If heating continues, coral starves to death. Once the algae are gone, the reef will erode, destroying fish habitat and exposing previously protected shorelines to the destructive force of ocean waves.
Damaged or dying reefs have been found from Réunion, off the coast of Madagascar, to East Flores, Indonesia; and from Guam and Hawaii in the Pacific to the Florida Keys in the Atlantic. The first mass bleaching occurred during the 1982-83 El Niño. A global bleaching event was confirmed in 1998, during a strong El Niño that was followed by a very strong La Niña, which brought warmer waters to places like Palau and Micronesia.
A second global bleaching event occurred in 2010, during a less powerful El Niño. Scientists first observed the most current global bleaching event, the third one, which began in mid-2014 in the western Pacific Ocean as the current El Niño strengthens. The bleaching events has persisted for 20 months, continuing to this day. It takes 10 to 20 years for the reefs to recover, and what is happening now is killing off reefs that have not been able to recover from the previous event in 1998.
The Great Barrier Reef stretches 1,000 miles along Australia’s northeastern coast, consists of 3,000 individual reefs, and is home to 1,500 species of fish. The Great Barrier Reef has been subject to the largest, most recent bleaching event because of El Niño.
In a survey of 520 individual reefs that make up the northern section of the Great Barrier Reef, 95 per cent were severely damaged, with only four showing no signs of bleaching. About 620 miles of reef that was previously in prime condition has suffered from severe bleaching.
The Great Barrier Reef Marine Park Authority has raised its bleaching warning to the highest alert and will begin to put limits on water pollution in place—to avoid further weakening of the reefs—while monitoring coral closely.
Simply put, the state of the Great Barrier Reef is a disaster. The precise quantity of coral that will die has yet to be determined; however, a recent survey off Cape York found the mortality rate to be 50 per cent.
The current pace of climate change may not give these damaged reefs sufficient time to fully bounce back. Before the 1980s, mass bleaching events were virtually unheard of. Today, they occur much more frequently, especially during seasons affected by El Niño
As more carbon dioxide is pumped into the atmosphere, the ocean becomes more and more acidic. In some cases, acidification can make corals more sensitive to bleaching at lower temperatures.
However, there are options to ensure that the integrity of the reefs is maintained. Some species of fish, like the rabbitfish and the spotlight parrotfish, play a crucial role, but these fish are in decline due to heavy fishing. Bans on fishing near the coral reefs will play a huge part in allowing these herbivore species of fish to maintain and help the reefs rebuild.
The most effective move to make in stopping the bleaching events will be to limit the burning of fossil fuels, since the ocean’s water is 30 per cent more acidic. The rate of change is expected to continue, making this the fastest in 300 million years.