12 interesting coral reef facts

Coral reefs are one of the most indispensable ecosystems on Earth.

What makes corals are so brightly coloured? Why do they turn white when they’re unhealthy? We’ve got you covered. Below, we’re sharing 12+ fascinating facts about coral reefs: The most biologically diverse ecosystem on Earth.

Corals reefs are large skeletons (because they’re made up of tiny animals a.k.a. ‘coral polyps’). They’re home to hundreds of plants and organisms, support fisheries and may host the answers needed to develop new cancer medication. 

How many of these coral reef facts do you know?

1. Coral reefs occur in more than 100 countries and territories whilst covering only 0.2% of the seafloor. They reside in tropical and semi-tropical waters.  

2. The single-celled algae, zooxanthellae, that live in the tissues of the coral polyps can fuel up to 90% of the reef-building coral’s energy requirements for growth and reproduction. Additionally, zooxanthellae are responsible for the vibrant colours of the corals!  

3. In return, the corals provide them with a home to reside in and nutrients to aid photosynthesis. Thus, fulfilling a mutually beneficial (‘symbiotic’) relationship! 

4. A healthy coral reef can limit coastal wave energy by up to 97%. That alone makes corals a crucial shoreline protector, like some other coastal ecosystems.

Coral reefs protect around $6 billion worth of built infrastructure from flooding around the world, from an economic perspective.

5. Large scale losses of coral reefs are due to a warming Ocean and climate change.

Land-based pollution of nutrients and sediments from agriculture, marine pollution, overfishing and destructive fishing practices, and outbreaks of coral diseases and crown-of-thorn starfish (see below image) are all causes of local coral losses. 

6. Coral reefs support at least a quarter of all marine species. What’s more: Coral reefs are a home to an average of 830,000 species (550,000 – 1,330,000). The range varies widely due to large populations of small cryptic species being difficult to sample.  

7. Astonishingly, scientists estimate that roughly 74% of coral reef species remain undiscovered! 

8. Ocean acidification is a major threat to coral reefs.

The decrease in pH (making water acidic) hinders corals and other organisms from forming their skeletons. This makes them especially vulnerable in juvenile stages.

The weakening of these skeletons also results in habitat loss, low reef biodiversity, coastline erosion etc. 

9. Coral reefs subjected to higher temperature levels increase the likelihood of abrupt and irreversible changes. According to the IPCC, a record-shattering warming world of 1.5°C would mean a 70-90% decline in coral reefs.  

10. Coral reef associated fisheries provide 70% of protein in the diets of Pacific Islanders. These fisheries support around 6 million people and are worth $6.8 billion annually.  

11. Corals can turn white due to coral bleaching. Climate change is a major driver of coral bleaching, and this process disrupts the symbiotic relationship with zooxanthellae.  

As the algae is dispelled by the corals in an attempt to protect themselves, the corals vulnerability increases and they lose a major energy source. If the heat stress persists, corals are likely to die.  

Over half of the our coral reefs are already lost.

12. Coral restoration is a relatively new nature-based solution. Nature-based solutions refers to an umbrella of methods for reviving ecosystems in the face of adversity. 

A 2020 review stated that coral restoration projects report a survival rate between 60-70% with a report stating that 1.5C warming would render this solution to be ineffective.

The authors of the review noted that most projects are small-scale and that we’ll still require large-scale climate action to tackle the root of this issue. 

With over half of the world’s coral reefs already lost, it is evident that coral reefs are declining due to a multitude of human pressures.  

Some warm water corals have reached adaptation limits. Nevertheless, scientists and local communities are working extremely hard to continuously build on existing solutions and quickly adopt innovative approaches. 

The existential threat of the rise in global temperatures means that climate change action is urgently needed to establish coral reef resilience.  

Act now.