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Increasing temperatures and carbon dioxide levels in the world’s oceans may actually speed the growth of starfish, according to research published this week in the Proceedings of the National Academy of Sciences. The results contrast with previous findings of global warming’s negative effects on the five-armed fish’s relatives.

“Mollusks, bivalves, clams and mussels respond negatively to increased carbon dioxide,” says Rebecca Gooding, a doctoral student in zoology at the University of British Columbia and lead author of the paper. On the other hand, she says, compared to their invertebrate cousins, “starfish are growing faster, getting bigger faster, and they’re eating more.”

The starfish’s saving grace, according to Gooding, is that it wears less armor than most other marine invertebrates. (One exception is soft-bodied animals like the sea anemone.) Oceans absorb about half the carbon dioxide humans release into the atmosphere, resulting in more acidic water. Many sea creatures suffer as lowered pH dissolves their calcified shells.

But the effect is not universal. “We need to be careful predicting how species are going to respond to climate change just based on which species they are related to,” says Gooding. “It’s very complex. We actually know very little.”

The researchers put starfish into tanks with carbon dioxide levels and temperatures ranging within current and future levels predicted by the Intergovernmental Panel on Climate Change. In water that contained a relatively high level of carbon dioxide, the sea star, Pisaster ochraceus, grew 67 percent more than its counterparts in tanks set at lower concentrations. An increase of three degrees Celsius (about 5.4 degrees Fahrenheit) boosted relative growth by 110 percent.

Of course, good news for one species doesn’t always apply to an entire underwater ecosystem. Starfish feed on smaller invertebrates, including species not found to do as well under changing ocean conditions.

The mismatch may have a dangerous downside. “This species of sea star just chows down on mussels,” says Gooding. “We expect mussels to grow smaller with rising carbon dioxide since they are stuck in a shell.” The starfish’s dependence on something with shrinking shells makes Gooding wary: “I think mussels are in trouble.”

Photo by Topyti via Flickr

7 Comments

1. 1. pgtruspace 01:46 AM 5/27/09

   says doctoral student Rebecca Gooding. “It’s very complex. We actually know very little.” says it all.

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2. 2. pgtruspace 01:59 AM 5/27/09

   Too bad there are no facts sited in the article just statements of opinions based on?????????????????????????????elevated levels of CO2. How high is up? May be Rebecca needs a nice fat research grant to learn a little more.

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3. 3. galaxy_man 08:37 AM 5/27/09

   The measured growth increase isn't an opinion, nor are the parameters that led to it. The fact that these starfish feed on species that are suffering negative effects from the same source is not an opinion.
   
   Apparently your argument is fixed on the point that this person is a grad student who admits that there is a lot to learn. So far that puts her way ahead of blowhards that act like they know everything and address nothing. And grad students in research fields are not exactly on the same level as someone getting their MBA.
   
   A lot of valuable findings are the results of work done by grads. For example, the discovery of superfluids in the form of He3. That's a pretty big one, wouldn't you say?

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4. 4. skavookie in reply to pgtruspace 01:22 PM 5/27/09

   Gooding's conclusions are based on two years of research and you can find the methods used and the exact parameters by looking up her article at a university research library. This is just a summary for laypeople, and thus does not contain technical details. And, SciAm misquoted her on a number of points. I suspect that she would have been annoyed that they used "starfish" instead of "sea star," as "sea star" is more correct (they are not fish), and she always uses the term "sea star."

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5. 5. Owl905 02:50 PM 5/27/09

   Interesting article. Including what kind of increased CO2 levels were used would have been been. The key implication of the study seems to be that ocean acidification will have a much stronger effect than a worst-case warming change.

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6. 6. MichaelPKaneko 03:06 PM 5/27/09

   Very interesting. It makes sense that rising CO2 levels will have different effects on different organisms. Too often, us laymen oversimplify things and only see in black and white! Anyway, such research is important, because it's quite possible that some pest organisms will thrive in increased CO2.

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7. 7. cornflower in reply to pgtruspace 07:20 AM 9/15/09

   Oh, no! We wouldn't want anyone to make money expanding our knowledge base!!!! The facts might get in the way of our opinions and force us to think more criticially about our own ideas!

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