The big cities of the sea

Author: Linda Bauere

If asked about climate change and the effect it has on our planet, what would you think about first? I, for one, would start thinking about the negative impact on rainforests, agriculture and hurricanes, not giving much thought to the thing that covers 71% of the Earth’s surface — water [1]. Seems bizarre, doesn’t it? As oceans hold about 96.5% of all of Earth’s water, we should be more concerned about their well-being. How could we do that? By taking care of the coral reefs — the big cities of the sea.  

To begin, we should start with the basics — what even is a coral reef? The coral reef is a large underwater structure that is made up from thousands of coral polyps — tiny animals related to anemones and jellyfish. These polyps extract calcium carbonate from seawater to form a hard exoskeleton, and with this process repeating itself the coral reef grows and thrives. However, the polyps alone are not enough to form a coral reef — they need to have a symbiotic relationship with an algae called Zooxanthellae, which creates energy through photosynthesis and is the main food source for the corals [2].

Why should we care what coral reef are? “Coral reefs are the big cities of the sea [3]”.

They are home to about 25% of all marine life and provide nurseries for a quarter of the ocean’s fish —  a few of those species have probably ended up on your plate at least once or twice [4].

This becomes more fascinating when we take into account that the reefs cover less than 2% of the ocean’s bottom [3]. By nurturing and providing for a quarter of the marine life, coral reefs provide an important food source to both the local communities and cities as well as to the world’s fisheries. Moreover, they are vital to the safe-being of coastal cities and in an event like a hurricane, a typhoon and even a tsunami they act as natural barriers. And, as technologies advance, more compounds from coral reefs are used in medicine — corals have evolved to have a chemical defence against predators, therefore scientists are working to research the medical potential of these substances and are starting to use them to treat diseases such as bacterial infections, heart disease, cancer and many more [2, 5].

So how can we take care of coral reefs? The easiest thing we can do is not damaging them any further as it takes a long time for coral reefs to be formed. To put this into perspective – on average corals grow 2.5 cm or less per year, and it has taken about 20,000 years for the Great Barrier Reef to become what we know it to be today [3]. Climate change and a rise in ocean temperature is the leading cause of coral bleaching — a term which is used when the coral turns completely white because the algae has left it, which leaves the coral more susceptible to disease (picture below). Therefore everything that we can do to prevent or slow down climate change will help the coral reefs.

Another major threat to coral reefs is pollution, for which humankind can take full responsibility.

In the words of ecologist Joleah Lamb, “after plastic comes into contact with a reef, the coral is 20 times more likely to be afflicted by disease” [6].

Nowadays, as #zerowaste becomes more popular with people making videos and sharing their stories of tips and ideas on how to reduce waste, it is becoming much easier to be friendly to our planet, thereby being friendly to the oceans and the coral reefs that reside there.

Whilst we tend to think that problems on the other side of the world have no impact on us, that isn’t necessarily true. Our planet can be defined as one large, beautiful, breathing organism full of life. As you may know yourself, if an organ, e.g., the liver fails, it has a negative effect on the rest of the human body. So why would our planet be any different? If we do nothing and let the coral reefs die out, the repercussions on our planet’s ecosystem will be drastic; at first affecting the coastal cities and communities but not stopping until the aftermath can be felt by each and every one of us. It is why I urge all of us to rethink our everyday habits to find out where we could do a little bit more to waste a little bit less.


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Article sources:

1. How much water is there on, in, and above the Earth? (2016, December 2). Retrieved from

2. Coral Reefs 101. Retrieved from

3. Knowlton, N. (2018, April). Corals and coral reefs. Retrieved from

4. Coral reefs. Retrieved from

5. NOAA. (2018, Juny 25). What does coral have to do with medicine? Retrieved from

6. Thompson, A. (2018, January 30). Where Plastic Goes, Coral Disease Follows. Scientific American. Retrieved from


Photo sources:

1. Photo by Shaun Low on Unsplash

2. National Ocean Service. What is coral bleaching?

Cover picture: Photo by Sagar on Unsplash

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