March 11, 2010

Maine's shrimp could serve as climate change barometer

— It's hard to imagine a creature more in tune with the environment than the Maine shrimp.

Timing is everything for an animal that lives five years and spawns just two or three times. It also helps that shrimp have one of nature's strangest and most efficient life cycles: All shrimp are male for the first half of their lives, and female for the second.

A new study published Friday in Science magazine shows that the northern shrimp, as the species is officially known, has even synchronized its reproduction to water temperatures changes and annual phytoplankton blooms.

And it suggests that the sensitive little crustaceans may be among the first critters to feel -- and show -- the effects of climate change in our backyard.

Most Mainers know northern shrimp as the small, sweet, pink delicacies sold each winter and spring in fish markets and along roadsides.

Offshore, they lead an equally colorful life. They hatch in the spring and float to the surface, eating plankton until they grow and descend to the bottom as juvenile males.

Shrimp reproduce as males when they're two years old, then transform into females and reproduce for two years before they die.

A key to their success, it turns out, is that the eggs hatch at just the right time to coincide with spring phytoplankton blooms, when there is so much baby shrimp food floating around the surface that it can actually be seen from satellites.

That's not as simple for the shrimp as it sounds.

Shrimp spend their brief adult lives on the dark ocean bottom and never come near blooming plankton.

So, to synchronize the egg hatching and plankton blooming, it seems, the shrimp key in to the temperature at the ocean bottom.

''They seem to have evolved the one thing they can basically control the time they extrude their eggs, and that seems to be timed in a way to the temperature regime they're in,'' said Anne Richards, a shrimp specialist at NOAA's Northeast Fisheries Science Center laboratory in Woods Hole, Mass., and a co-author of the new Science article.

The shrimp don't know that they're doing this, of course, and neither did Richards and the other scientists until they began comparing satellite images of the Gulf of Maine and other shrimp waters with egg hatching times.

As long as ocean temperatures stay in sync with the plankton blooms, the larvae will rise to the surface, find lots of food to eat and grow up to be parents, first fathers and then mothers.

But plankton blooms are affected by sunlight as well as the ocean temperature.

So if the water warms up sooner or later in the season than usual, the baby shrimp might not find a lot of plankton to eat.

All of which suggests that the shrimp, and the Mainers who love to eat them, could feel the effects of climate change sooner than most.

If ocean temperatures continue to rise as scientists have projected, it could throw off their timing, and their reproduction.

Of course, there are a lot of complicating factors in the ocean.

It's unknown how climate change will affect plankton blooms, for example. It's also unclear how fast shrimp might adapt to the changes, given their ability to cope in other unlikely ways.

''We like to simplify (nature) because we can handle that conceptually, but really there's a lot more complexity to things,'' Richards said. ''It makes it really hard to predict what's going to happen.''

For Richards, however, it's another good reason to keep an eye on shrimp.

''They're very interesting critters, and tasty too.''

Staff Writer John Richardson can be contacted at 791-6324 or at:

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