Coral bleaching- the rundown

Coral bleaching is a mass phenomena sweeping our corals all over the world. It leaves corals vulnerable to disease, stunts their growth, affects their reproduction and has negative affects for the multitude of animals communities that depend on the reefs. So what is it, what are the effects, and can it be stopped?


Over the last century, the average temperature of tropical oceans has increased by 0.1 degrees celsius. Why? Our oceans absorb vast quantities of heat as a result of increased concentrations of greenhouse gases in the atmosphere which have primarily come from fossil fuel consumption, for example coal, crude oil and natural gas. This ties in with the increase occurring in the last century, as this coincides with industrial revolutions that have occurred around the world in the past 100 years and increased use of these fuels tenfold.


These temperature increases stress the corals out. When corals are stressed by changes in temperature, light or nutrients, they expel the symbiotic algae that lives in their tissues, causing them to turn completely white. The algae, called zooxanthellae, are photosynthetic, and provide their host coral with food in return for protection. Without this algae, the coral bleach and die.


The animals that depend on corals for food or habitats are affected negatively by this. When corals die it changed the abundance and composition of reef fish assemblages and can even cause fish to die as they lose their home or source of food.


The effects of coral bleaching impact humans too. Degraded or dead coral reefs are less able to provide the ecosystem services on which local human communities depend. For example, degraded coral reefs may not be able to sustain the accretion rates necessary to provide shoreline protection services. Losing reefs also means losing tourism, which is fundamental for many people and communities that rely on that income. Economically we also see that coral bleaching events shifts in fish communities, which can translate into reduced catches for fishers targeting reef fish species. This in turn effects food supply and associated economic activities.

Reefs also provide many pharmaceutical compounds, and without them we may lose sources of highly important medical resources (e.g. drugs to treat heart disease, cancer etc).


But all hope is not lost. There are ways we can help, both from home and when visiting places where reefs exist:


  • When visiting coral reefs, practice safe and responsible diving/snorkelling. Don't touch or break off parts of the reef (if you want a memento, take a photo- it's more environmentally kind and lasts longer) and ensure your boat doesn't anchor onto the reef. Also, be wise with your suncream choices. What many people don't know is that some ingredients in sunscreen can be harmful to and even kill corals, so inform yourself on a sustainable option or, better yet, wear a long-sleeved t-shirt or rash-guard to cut out the need for suncream completely!


  • At home, there are also many ways to help, which is probably more viable given our current COVID circumstances! Recycling and proper waste disposal is paramount, not only for coral reefs but for our planet in general. Plastic especially often ends up in oceans. affecting both the animals and the environments underwater, so be wise and dispose of your rubbish correctly. Minimising fertiliser use is also a good way of helping. The overuse of fertilisers on grass impacts water quality as nutrients from the fertilisers (such as nitrogen and phosphorous) end up in oceans. These nutrients pollute the water and can harm corals. Saving energy at home and work is also another quick and easy way to reduce the reliance of fossil fuels, which after all, is the biggest cause of our corals dying. And finally, spread the word! Learn what you can, do what you're able to, and inform the people around you. If you can, reduce your reliance on non-renewable energy, and advocate for more wind farms or hydroelectricity dams, or purchase some solar panels for your house!


As always, every little helps, and one person can make all the difference.


Let me know any things you decide to try, or other tips you recommend!


We can all DO MORE for our reefs from our home, and we can do it now.



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