Wild Things

The weird and wonderful in the natural world

Sarah Zielinski

Wild Things


Wild Things

Coral competitor becomes ally in fight against starfish

crown-of-thorns starfish

An outbreak of crown-of-thorns starfish (one shown) can devastate a reef. But algae, a coral competitor, may protect coral from the predatory starfish, a new study finds.

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Coral and algae don’t get along. On reefs, algae compete with coral, reducing coral growth and survival. Scientists suspect that the algae may also promote harmful bacteria or coral-eating species, causing further coral damage.

But coral have an even bigger worry: the crown-of-thorns starfish. These are large (up to about a third of a meter) seastars covered in venomous spikes that feed on coral polyps. Outbreaks of the starfish, which are native to the Indo-Pacific, can damage large sections of reef and even kill an entire coral colony.

So the combination of starfish and algae sounds bad for coral — but it may not be, a new study finds. The algae might protect the coral from the predatory seastars, Cody Clements and Mark Hay of Georgia Institute of Technology in Atlanta conclude August 26 in the Proceedings of the Royal Society B.

Clements and Hay performed a series of experiments in Fiji on Montipora coral, a favorite prey of crown-of-thorns starfish. They photographed reefs that had been attacked and those that hadn’t, quantifying algae cover on both. They planted tiny coral surrounded by various amounts of Sargassum algae to see how coral growth was affected. And they set up feeding trials for the starfish to see whether they would attack coral when algae was present.

The more algae that was around, the more coral growth declined, the researchers found. But the Sargassum seemed to have a protective effect when the starfish was present: There was less predation on reefs that had more algae. Attacked colonies had about 8 percent algal cover compared with 55 percent on reefs that were untouched. And in the feeding experiments, corals without any algae were always attacked while those with higher amounts of Sargassum were rarely consumed.

The algae could even force the seastars to change their feeding preferences. Crown-of-thorns prefer Montipora coral over Porites coral. But if the Monitpora is surrounded by algae, the starfish settle for the less-preferable Porites meal, the researchers found.

What is it about the algae that turns the starfish off? It is probably the physical structure of the Sargassum, the researchers suggest. When they put fake plastic Sargassum around the coral, seastars were much less likely to attack, similar to what happened with the real algae.

Animals

A world of mammal diversity has been lost because of humans

By Sarah Zielinski 9:55am, August 26, 2015
Humans have eradicated large mammal biodiversity in most regions of the globe, a new study finds.
Plants,, Animals

What fairy circles teach us about science

By Sarah Zielinski 6:30am, August 20, 2015
Science can’t yet tell us how fairy circles form, but that’s not a failure for science.
Animals,, Conservation

A UFO would stress out a bear

By Sarah Zielinski 12:00pm, August 13, 2015
Scientists need to know how animals, such as bears, react to the drones being used increasingly to study them.
Animals,, Conservation

Cougars may provide a net benefit to humans

By Sarah Zielinski 3:27pm, August 12, 2015
Cougars have disappeared from the eastern United States. If they returned, they’d kill deer, preventing many car crashes, scientists find.
Animals,, Conservation

Gibbons have been disappearing from China for centuries

By Sarah Zielinski 4:00pm, August 6, 2015
Gibbons are now found in only a small area of southwestern China. But they once thrived across much of the country, records show.
Animals

Don’t let Cecil the lion distract from the big conservation challenges

By Sarah Zielinski 4:11pm, August 4, 2015
Cecil the lion’s death rocketed across the news and social media. But there are bigger conservation challenges that need attention, too.
Animals,, Ecology

How bears engineer Japanese forests

By Sarah Zielinski 1:00pm, July 31, 2015
In Japanese forests, black bears climb trees, breaking limbs. Those gaps in the forest provide light to fruiting plants, a new study finds.
Animals,, Plants

On the importance of elephant poop

By Sarah Zielinski 4:57pm, July 28, 2015
Asian elephants are key dispersers for tree seeds. A new study finds that buffalo and cattle can also disperse the seeds, but not nearly as well.
Animals,, Oceans,, Climate

Sea level rise threatens sea turtles

By Sarah Zielinski 4:00pm, July 22, 2015
Sea level rise is causing coastal areas to be inundated with water. Even short periods of being wet can kill sea turtle eggs, a new study finds.
Animals,, Oceans

Eyewitness account of a dolphin birth takes a dark turn

By Sarah Zielinski 11:17am, July 21, 2015
Scientists witnessed the first wild birth of a bottlenose dolphin — and an attempt at infanticide.
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