CORAL REEFS

SHARKS HELP TAKE CARE OF CORAL REEFS

On reefs without sharks, smaller predators (known as mesopredators) are more abundant. These mesopredators are usually the prey or competition to sharks. This is called "mesopredator release" in ecology. It's common when a top-level predator is removed from the food chain... and it happens both in the ocean and out of it. 

Sounds great, if you're a fisherman wanting to catch these mesopredators, right? Wrong!

So what's the big deal?

Keeping mesopredators in check means small reef fish can thrive - and they're the ones who actually take care of the coral.
​Often herbivores, they eat off the algae that can overwhelm coral (especially if it is young or recovering - like, from a recent storm). In areas with healthy shark populations, the corals will actually recover faster from bad events (like bleaching) and have a lower chance of catching a disease and getting sick!

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large, mobile sharks may also be an important source of nutrients for coral reefs and their creatures. how?


​Shark poop has nitrogen (and other minerals) in it. When a shark poops over a coral reef, that gets deposited to a reef ecosystem!
​This amount probably helps keep it healthy- kind of like fertiliser.

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Why are coral reefs so important?

Coral reefs are one of the most diverse ecosystems in the planet. They also...
  • protect coastlines by acting like a buffer, and protecting our coasts from waves, storms, and floods. This not only helps saves lives, but helps us avoid property damage and erosion.
  • coral reefs have multiple uses: a spawning ground, nursery, refuge and feeding areas for a variety of animal.
  • are a source of nitrogen (may be in thanks to that shark poop) and other essential nutrients for marine food chains - it also helps with nutrient recycling.

WHAT THREATS TO CORAL REEFS FACE?

OCEAN ACIDIFICATION

Ocean acidification dissolves the very skeleton of corals... and that's what makes up the structure of a reef. If this persists, it makes it difficult for corals to grow. No coral reefs, no benefits to the ocean (and us).

CLIMATE CHANGE

As the ocean warms, the symbiotic relationship between corals and microalgae breaks - and if the temperature is too high, this microalgae may not be able to recover. This microalgae often is what gives coral its vibrant hues... and when expelled, a coral is "bleached."

disease

Higher temperatures (thanks to climate change) means corals are more susceptible to illness, and in their weakened state allows for disease-causing organisms to grow and spread faster. 

And the list goes on... ​
overfishing, fishing using cyanide and dynamite, pollution from sewage and agriculture, massive outbreaks of predatory starfish, invasive species, and sedimentation from poor land use practices. Just the tip of the problems that coral reefs face.