Fish Acting as Lawnmowers Help Coral Reefs Recover


Written by Jaymi Heimbuch, Treehugger

A major barrier for corals trying to recover from damage is the overgrowth of algae. Too much algae, and coral larvae aren’t able to find suitable spots to settle down and grow up. But, with the help of a few certain types of fish, coral reefs stand a better chance of bouncing back from problems like storms or predation.

PhysOrg reports on research from University of California, Santa Barbara that found in some places, fish can be the key to corals’ survival.

The South Pacific island of Moorea, in French Polynesia, seemed to bounce back easier after the loss of live coral in the 1980s. The researchers wanted to understand why. Crown-of-thorns sea stars had fed on corals, and algae grew on the skeletons. Normally, that’s a bad sign. But in this area, there were larger numbers of bigger, fatter parrotfish and surgeonfish. It turns out, that the coral reef nearest the island was a nursery for these fish, which could grow fat on the algae, and in turn, help the algae stay mowed down, like a well manicured lawn. This gave space for coral larvae to take hold and rebuild the outer reefs that suffered the bulk of damage from both the sea star infestation and cyclones.

Because of the help of these “thousands of tiny lawnmowers,” the reef bounced back more quickly, and it explains why many reefs in the Caribbean, which don’t have healthy populations of parrotfish and surgeonfish due to overfishing, have a far more difficult time recovering from damage. The study shows yet another reason why protecting reefs from overfishing is a key solution for coral conservation. But it’s not about protecting just any part of coral reefs — it is vital to protect those that act as nurseries too.

From PhysOrg:

Managers have tried to reverse the trend of overfishing through the creation of Marine Protected Areas (MPAs), where fishing is severely restricted or prohibited. “Our results suggest that this strategy may not be enough to reverse the trend of coral reefs becoming algal reefs,” said Brooks. “Our new and very novel results suggest that it also is vital to protect the fringing reefs that serve as nursery grounds. Without these nursery grounds, populations of parrotfishes and surgeonfishes can’t respond to increasing amounts of algae on the reefs by outputting more baby herbivores.”

In short, the research team found that by using MPAs, managers can help protect adult fish, producing bigger, fatter fish. “But if you don’t protect the nursery habitat the babies produced by these bigger fish, or by fish in other, nearby areas you can’t increase the overall numbers of the important algae-eating fish on the reef,” said Brooks.

The researcher have uncovered another important clue that could make marine protected areas all the more successful if implemented correctly.

This post was originally published by Treehugger.


Related Stories:

Why Some Fish Fart

Overfishing 101: How Science Helps Managers End Overfishing and Rebuild Depleted Fish Populations

Update on the Great Pacific Garbage Patch (Yes, It’s Still There)


Photo from orkybash via flickr


Duane B.
.4 years ago

Thank you for sharing.

Carrie Anne Brown

interesting article, thanks for sharing :)

Craig Q.
Craig Q6 years ago

Don't give so much hope on grazing fish to clean algae off of coral reefs. Address the real issue that coral need clean clear nutrient free water in which to exist. Sewage, fertilizers, nutrients and atmospheric deposition of pollution exacerbate algal growth. Fish do their part but without clean water the fish cannot keep up with massive algal blooms. For more information visit the science section of and for free downloadable images of algal covered reefs in the Caribbean visit Thanks Craig Quirolo Photographer and curator of the archive.

Diane L.
Diane L6 years ago

This is called "balance of nature". When one species becomes too abundant, with no predators, or lack of them, then the entire environment suffers. Look at the devastation around Victoria Island in B.C. when Russian hunters almost made extinct the sea otters there.

Debra M.
Debra G6 years ago

Another part of the destruction of the coral reefs is the crown of thorns starfish, which has gained a terrible foothold on the reefs because of the trade in exotic shells, and the one known predator of the crown of thorns is a beautiful crustacean. Natives harvest this snail in unsustainable numbers in order to sell them to Westerners to adorn their own homes with. Stop buying sea shells! Leave living animals alone, and let them live. Then the oceans will begin to heal as well. If Mankind stops over doing everything we do every where we go.

Lisa Lungul
Lisa Lungul6 years ago

That story gives me hope for the future of our world in healing itself...only we need to stop destroying it first.

Karen B.
Past Member 6 years ago

Once man has destroyed his ownself,
Mother Earth will heal Herself.

Steffi Denys
Steffi Denys6 years ago

I don't understand why the most beautiful things in the world always have to be destroyed.

Rossy Osborne
Rossy Osborne6 years ago

Wonderful that these folk are finally learning to allow nature do it own thing, in its own way!
Interesting article thank you.

Jim Gayden
Jim Gayden6 years ago

Perfect example of a ecosystem symbiosis that has evolved over a millenia. Every species is vital in a complex ecosystem in order for it to remain healthy.