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North Carolina Mussels on the Brink?

January 23, 2013

by Meg Lowman

It’s the biggest conservation crisis that no one talks about.
—Paul Johnson, director, Alabama Aquatic Biodiversity Center

What group of species is more common in North America than anywhere else?

Freshwater mussels. But this unique group of organisms rarely reaches the headlines or even reaches the center of discussion in school biology classes. Even more amazing is the fact that, of the 297 species found on our continent, two-thirds are concentrated in the Southeastern United States because of the region’s unique geology and relatively stable environment over the past 60 million years. Mussels provided an important food source for Native Americans, fostered the button industry in the 1800s, and constitute an essential part of freshwater food chains.

Mussels operate as filter feeders, removing bacteria and algae from water, which ultimately contributes to water quality. Of the 10 to 700 animals found in one square meter of stream bottom, each one filters approximately one liter of water per hour — essentially providing a free water-filtration system for our freshwater streams.

But mussels are in great danger. Twenty-five species already are extinct, and about 75 percent of mussel species are at some level of peril. The biggest threat to mussels was the widespread construction of dams in the early 1900s, and more recently, deforestation and mining that create muddy waterways. Mussels cannot survive in these polluted, silt-laden waters; many species are suffering a rapid population crash. In a sense, mussels serve as a “canary in the coal mine” for water quality.

Their population declines indicate a decline in water quality that can affect humans and agriculture, so monitoring mussels now represents a key indicator of stream health. Mussels are unique among all bivalves because they have a parasitic larval stage on the gills or fins of fish. So, if their fish hosts are impacted by pollution, the reproduction of mussels is also in jeopardy.

Some biologists have developed programs to repopulate mussels by rearing them in hatcheries and releasing them into the wild.

Scuba diving for Missouri mussels

Scuba diving for Missouri mussels

Dr. Art Bogan, research curator of aquatic invertebrates at the N.C. Museum of Natural Sciences, is a global expert on freshwater mussels. In his briefcase-tool kit, he carries scuba gear, rubber waders, dip nets, waterproof collection boxes and a thermos of coffee. Bogan is a freshwater detective, finding the mussel species of the Southeast and figuring out why this region is a global biodiversity hot spot for these unique critters. He recently discovered and described two new species of mussel from our region, and he knows there are other new species as yet undiscovered.

Are any readers interested in scuba-diving in local streams, with a chance to find critters never seen before by human eyes? Well, perhaps a career as a malacologist (scientist who studies mollusks) is for you!

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