The Great Barrier Reef has experienced a third mass coral bleaching event since 2016 according to the scientist carrying out aerial surveys over hundreds of individual reefs.
“Australia’s lead management agency for the Great Barrier Reef can confirm mass bleaching is occurring on the Great Barrier Reef, with very widespread bleaching detected,” the country’s Great Barrier Reef Marine Park Authority (GBRMPA). It follows the worst outbreaks of mass bleaching on record killing about half the shallow water corals on the world’s biggest reef system in 2016 and 2017.
Hughes, director of the ARC Centre of Excellence for Coral Reef Studies at James Cook University and one of the world’s leading authorities on bleaching and the Great Barrier Reef, said: “We know enough now that [the bleaching] is more severe than in 1998 and 2002. How it sits with 2016 and 2017 we are not sure yet.”
Global heating caused by escalating atmospheric greenhouse gases is a major threat to the world’s coral reef ecosystems. Coral bleaching most often occurs when ocean temperatures are too warm for long periods of time, effectively cooking the delicate structures and leaving them weakened and sick. They can recover if temperatures go back to normal, but will die if the ocean doesn’t normalize.
The UN’s Intergovernmental Panel on Climate Change found the published evidence suggested a majority of tropical coral reefs would disappear even if heating was limited to 1.5C and would be “at very high risk” at 1.2C. The globe has warmed about 1C since the industrial revolution.
Not all bleached corals die. Corals bleach when they sit in waters that are unusually hot for too long. They can recover if temperatures fall, but are often killed when high temperatures are sustained.
A five-yearly report by the major marine park authority last year found the reef’s outlook had deteriorated from poor to very poor, and warned the window of opportunity to improve its future was “now”.
The latest mass bleaching comes as Unesco’s world heritage committee is scheduled to assess the reef’s status this year. It is the first time the committee will have considered the natural wonder’s world heritage status since the back-to-back bleaching events.
The GBRMPA said that the corals impacted by the mass bleaching may recover, but issued bleak predictions for reefs deeply affected by the dramatic levels of heat.
When you swim with sunscreen on, chemicals like oxybenzone can seep into the water, where they’re absorbed by corals. These substances contain nanoparticles that can disrupt coral’s reproduction and growth cycles, ultimately leading to bleaching.
Humans might be responsible for this contamination, but we’re also capable of helping heal these fragile underwater ecosystems. On May 1, 2018, lawmakers in Hawaii passed a bill banning the sale of sunscreens containing oxybenzone and octinoxate, another harmful chemical. Hawaii is the first state to pass such a measure.
Palau, Key West and the US Virgin Islands have introduced bans on harmful sunscreens. These bans started in 2020 and additional bans go into effect in the coming years. Here’s how you can protect both your skin and coral reefs.
Even if you don’t swim after applying sunscreen, it can go down drains when you shower. Aerosol versions of sunscreen can spray large amounts of the product onto the sand, where it gets washed into our oceans.
“We recommend the use of Reef-safe sunscreen free of oxybenzone,” says Peter Gash, managing director of Lady Elliot Island, near the Great Barrier Reef. Choose mineral-based sunscreens that use zinc oxide or titanium dioxide “non-nano” size particles that can’t be ingested by corals.