Our horror, another mass coral bleaching is possible in the Great Barrier Reef. With water temperatures reaching upto 3℃ higherIn some areas, it was higher than the average. This would be the sixth and fourth such event since late 1990s, respectively.
Today, a United Nations monitoring mission arrives in Queensland to inspect the reef. consider listing the World Heritage site as “in danger”.
As coral reef scientists, we’ve seen firsthand how the Great Barrier Reef is nearing its Tiping pointThe reef will cease functioning as an ecosystem once it reaches that point. This is not due to climate change exacerbating heatwaves in the oceans, but also higher ocean acids, loss of oxygen and pollution.
Scientists are also at their tipping point. The reef is suffering environmental conditions so extreme, we’re struggling to simulate these scenarios in our laboratories. Despite Australia having Facilities of the highest qualityWe are literally beating our heads against a wall every year as the situation worsens.
It’s getting harder for scientists to predict how these conditions will affect individual species, let alone the health and biodiversity of reef ecosystems. But let’s explore what we do know.
What is coral bleaching, and why does it occur?
Corals are animals that live in a mutually beneficial partnership with tiny single-celled algae called “zooxanthellae” (but scientists call them zooks).
Zooks provide energy and colour to corals, and the coral provides them with a home in coral tissue. The coral expels toxins from the coral when the alga is under stress, such as in too hot water.
The corals become starved if there is no algae. They lose their vibrant colours and the coral tissue reveals the bright white limestone structure.
If stress conditions are relieved, coral can grow back and recover over many months. But if stress persists, the corals can die – the skeletons begin to crumble, removing vital habitat for other species.
We had hoped to get a reprieve.
Scientists and managers hoped for a reprieve in this year’s drought. The Great Barrier Reef was a large part of this. In the initial stages of recoveryFollowing the 2016 and 2017 bleaching events.
In the tropical paradise of northern Queensland, we’ve been wishing for cloudy days and cooler temperatures, hoping for rain and even storms (but not big ones). These conditions typically come with La Niña – a natural climate phenomenon associated with cooler, wetter weather, which has now happened Two years consecutively.
But despite these effects of La Niña, climate change meant 2021 was one the hottest years ever recorded. Now, at the tail end of Australia’s summer, the reef is experiencing another marine heatwave and is tipping over the bleaching threshold.
There’s not enough time for coral to recover between events. Even the most robust corals require some time to recover. It took nearly a decade for recovery. It is not clear that corals are adapting to these new conditions.
Climate change is making it worse. La Niña and its counterpart El Niño more variable and less predictable. This means that Australia will not only experience more intense heatwaves but also flooding, droughts, and storms.
How will this impact marine life?
A healthy Great Barrier Reef It is your homeThere are at least 1,625 fish species, 3,000 molluscs species, and 630 echinoderms.
Coral reef life can choose to adapt to changing waters or move on.
1. Can they adapt?
Over generations, species can make changes at the molecular level – their DNA – so they’re more suited to or can adapt to new environmental conditions. For species with rapid generation times, this evolution may be possible. damselfishes.
But reef species with slower generation times can’t keep pace with the rate we’re changing their habitat conditions. This includes the iconic potato codMost sharks take around a decade to reach sexual maturity.
2. Can they move?
Some species are reef fishesYou may find yourself moving to cooler waters sooner than the harmful effects of global warming.
But this option isn’t available to all species, such as those that depend on a particular habitat, certain resources, or protection. This includes coral. coral-dwelling gobiesAnd several damselfishes.
A citizen science project called Project RedMapDocumenting has been done by. The poleward migration of species reef fish speciesClimate change. Studies have shown thatIt is more likely that larger, tropical fishes can survive in temperate water than those with high swimming abilities, such as some butterfliesfishes.
3. They can even die
The third option is one we don’t like to talk about, but is becoming more of a threat.
If marine life can’t adapt or move , we’ll see Local scale extinctions– Total extinction of certain species and dramatic declines among fish populations.
Listing the reef as ‘in danger’
While the reef is bleaching, UNESCO delegates have arrived in Queensland to monitor its health, as the World Heritage site is once again being considered for an “in danger” listing.
The visit will likely include seeing the bleaching currently occurring, the damage to the reef still apparent from past events, and they’ll hear firsthand from scientists and managers who’ve witnessed these impacts.
Listing the Great Barrier Reef as “in danger” would raise the alert level for the international community and hopefully inspire climate action.
Reducing the major source of stress the reef faces – climate change – will require ongoing collaborations between Australian and international governments, with work on local management issues also involving business owners, reef managers, Traditional Owners, scientists, civil society groups, and other stakeholders.
We’ve known for a long time the most important step to save the reef: cutting emissions to stop global warming. Indeed, Future projections of coral bleaching from the 1990s suggested that frequent and severe events would begin from the late-2010s – and they’ve been alarmingly prescient.
The Great Barrier Reef’s continuing demise is one of the most visible examples of how our inaction as humans has profound and perhaps irreversible consequences. We are rapidly approaching the tipping points.