When you think of the Great Barrier Reef, what comes to mind? For many of us, we're picturing tropical weather, an abundance of ocean wildlife, and bright, vivid colours.
Unfortunately, in recent decades, the vibrancy of the Great Barrier Reef, and many other coastal reefs around the world, has been dulled by a phenomenon known as coral bleaching, where coral loses its bright colours and turns white. In 2020, the Great Barrier Reef experienced its most widespread bleaching event on record – around 2300km of coastal reefs were severely bleached. This is the third mass bleaching event on the Reef in five years.
Widely regarded by scientists to be a consequence of climate change, coral bleaching is not only an eye sore, but a warning of what's to come of the Reef if governments continue to ignore the reality of global warming.
What causes coral bleaching?
Just like how humans can develop grey hairs when they're feeling pressure, coral bleaching is a stress response, specifically heat stress.
As the summer months continue to get hotter and hotter every year, water temperatures increase too – and it doesn't take much for coral bleaching to occur! If the water temperature increases by even just one degree Celsius for four weeks, it can result in coral bleaching.
When coral is under stress, the microscopic algae that gives coral its vibrant colour, zooxanthellae, is expelled, revealing their white skeletons. But this is more than just an aesthetic issue. Zooxanthellae enables the process of photosynthesis to take place – how coral gains the nutrients to survive. So, while bleaching doesn't kill the coral immediately, it is at a much greater risk of starvation and disease.
Coral bleaching affects more than just the coral – it affects the entire ecosystem of the reef.
Bleached coral will likely grow and reproduce at dramatically lower rates. Coral is a key habitat for many fish and ocean wildlife, so as coral continues to shrink in size and numbers, so too does the population of species that rely on coral for food and shelter.
What can we do?
The good news is coral can recover from bleaching over time – but only if temperatures drop, and ocean conditions return to normal. Unfortunately, according to the Intergovernmental Panel on Climate Change's (IPCC) modelling, the temperatures of the surface layers of the Ocean is predicted to rise by 1-3 degrees celsius by 2100 if we don't intervene.
Negligent governments and corporations that continue to pollute our oceans must be held accountable – we can do this by making our voices heard on social media, contacting our local representatives, and voting for climate action. Never underestimate the power of collective action!
On an individual level, there are lifestyle changes that we can all make that will benefit our coral reefs:
- Recycling, and proper disposal of rubbish, so that debris does not make its way into our oceans!
- Minimise use of fertilisers on gardens, as they can get washed into our waterways that eventually end up in our oceans!
- Reduce our energy consumption (walking more, using public transport, turning off the lights, etc.), which will in turn reduce our greenhouse gas emissions, which cause temperatures to rise!
- Reduce stormwater runoff, and prevent water pollution, by installing water catchments or rain gardens on your home!
Coral bleaching is a symptom of climate change, but it doesn't need to be the death rattle. We can make changes, big and small, to protect our coral reefs, and ensure a brighter, and more colourful future for all ocean life!
Header Image: Unsplashed