Rougher Waters Threaten Blue Mussel

Do you think you could hang onto the wing of an airplane while it zipped across the sky at 600 miles per hour?

Not a chance, yet that's equivalent to what all sorts of marine creatures do, day in and day out, in the intertidal zone where the sea meets the shore.

"It's a very physically stressful environment," says Emily Carrington, assistant professor of biology at the University of Rhode Island, who admits to somewhat of an obsession with the critters that inhabit one of Earth's most difficult regions. She believes they may be able to tell us much about what the future holds.

"They get bashed by waves, with water velocities of 20 meters per second," she says. "And when the tide goes out, they can get fried to a crisp, or heated up, dried out, or frozen. This is all a typical day in the intertidal zone.

"It's really a tough place to make a living."

But it's hardly a dead zone.

Key Species

"The weird thing is it's one of the most diverse habitats that we know," Carrington says. "There's more diversity in terms of species and body design" than almost anyplace else, and they even look different.

"It's not that they're all flat, or all round," she says.

All that could be changing, right before our eyes, at a pace so slow and in an environment so tumultuous that it's almost impossible to see it. A growing number of scientists believe the planet is getting warmer, and the climate is being influenced more and more by such events as El Nino, the warming of the Pacific Ocean that causes huge breakers to pry the sand out from under homes along the California coast.

While she was working on her doctorate degree at Stanford University a few years ago, Carrington became fascinated with one particular species that lives in the intertidal zone — the blue mussel. Using nothing but tiny threads, or as Carrington puts it, "nature's little bungee chords," these creatures can hang onto rocks that are being battered by waves driven by hurricanes and violent storms.

If they lose their grip, the surf likely will carry them into deeper water to the delight of predators that couldn't touch them in the intertidal zone. So they hang on or die.

And that set Carrington to wondering. Is there a point at which the waves become so violent that the blue mussel doesn't have enough muscle to stick around? Would they perhaps work their way into calmer waters, abandoning the rocky points they now dominate?

The lifestyle of the blue mussel might serve as somewhat of a barometer, giving scientists one more trail to follow as they try to figure out just what's going on in the murky waters of global climate change. Carrington landed a $320,000 grant from the National Science Foundation to see what she could learn from the blue mussels living at the edge of Rhode Island's Narragansett Bay.

As is nearly always the case, it turns out that it's much more complicated than it seems on the surface. The blue mussel is a "filter feeder," meaning it sucks in sea water, extracts what it needs, and spits out the rest. That results in cleaner water, a necessary condition for other species. It also serves as a habitat for many other creatures, providing warmth from the midday sun and a place to hide from predators.

"It's a keystone species," Carrington says. "If you take them away, other things can't live there." So if the storms get too violent and sweep the blue mussels away, other species and the entire coastal ecosystem will pay a high price.

Scientists have known for years now that the blue mussel can raise or lower its ability to hold onto the slippery rocks. Its staying power in the winter, for example, is twice that of the summer. It is generally believed that the mussel anticipates the approach of winter, growing more threads to increase its strength, so it would seem that it is well suited to adapting to changing conditions.

But Carrington believes it may turn out that the mussel's adaptation may come at a high price.

Gripping or Reproducing

"They can produce more threads [to increase their holding power] but the problem is they're not free," she says. "They [the threads] cost energy, and that may take energy away from reproduction, or how fast they can grow."

Her early research indicates that the mussels do not spawn while they are producing threads to increase their winter strength, so it may be that they must choose to do one or the other.

So she will spend the next few years collecting mussels from the Rhode Island shoreline "to bring them into the lab and play around with their reproductive cycle," she says.

She will wait until they are ready to reproduce, then hit them with large simulated waves to see if she can get them to do both, she says.

The world may not be waiting impatiently for the answer, but Carrington's research is typical of the kind of work that scientists must do to fill in the blanks and answer the crucial questions related to global climate change.

The blue mussel may tell us a few secrets. If it starts disappearing, or heading for calmer waters, the seas are, indeed, getting rough.

Lee Dye’s column appears weekly on A former science writer for the Los Angeles Times, he now lives in Juneau, Alaska.