Symbiosis meets Climate Change - Science Update

A trio of co-dependent creatures that like it really hot and how the warming world is causing corals and their algae partners to break up.
18 March 2007


This week for the Naked Scientists, symbiosis meets climate change. In case you don't remember from school, symbiosis is when totally different types of organisms live together in a mutually beneficial relationship-- sort of like marriage. I'm going to talk about a trio of co-dependent creatures that like it really hot. But first, Chelsea tells us how the warming world is causing corals and their algae partners to break up.

Even if you're worried about global warming, it probably seems like a fairly distant threat. But to coral reefs it's a clear and present danger. Evolutionary ecologist Drew Harvell of Cornell says warm temperatures seem to weaken corals' immune systems while at the same time causing diseases to flourish: a one-two punch. What's more, corals have a symbiotic relationship with a type of algae that provide them with oxygen and nutrients.

DREW HARVELL (Cornell University):

And the algae are actually very sensitive to changes in temperature and so even a one or two degree increase in temperature can cause the symbiosis to fall apart and the coral can die.

In fact, scientists have documented several cases of heat-related coral death around the world. Harvell and others hope to save those that remain by finding ways to boost their immunity, kill their diseases, and protect them from people.

Thanks, Chelsea. There's a kind of grass called "panic grass" in Yellowstone National Park here in the U.S. that thrives in hot geothermal soils, which can reach 50 degrees Celsius. It was recently discovered that a kind of fungus on the plant's roots makes this possible: neither the fungus nor the grass can withstand the high temperatures alone.

But now, researchers have found that the fungus confers this heat-resisting power only when it's infected with a virus. Marilyn Roossinck of the Samuel Roberts Noble Foundation in Oklahoma says they were able to reveal the three-way dependency by curing some of the plants of the virus.

MARILYN ROOSSINCK (Samuel Roberts Noble Foundation):

When the plants were colonized with the fungus infected with the virus, then they were heat tolerant. And when they were colonized with the fungus without the virus, or with no fungus, they died under the heat stress. Roossinck says understanding survival mechanisms like these isn't just academically interesting.

With the global climate changes that we are all facing now, we're going to see a lot more extreme environments on the planet, and that would include higher temperatures, probably also more periods of drought. So we need to understand how plants normally tolerate natural extreme environments. That may better equip us to grow crops when environments that seem extreme today become more normal.

Thanks, Bob. Next time we'll talk about how some scientists are using sound to make the lovely sights of public aquaria accessible to the visually impaired. Until then, I'm Chelsea Wald... -

...and I'm Bob Hirshon, for AAAS, The Science Society. Back to you, Naked Scientists...


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