ADRIAN MA, HOST:
Scientists are studying an invasive species of algae they believe can cause an increase in mercury levels in the food chain. From member station WHQR in Wilmington, North Carolina, Kelly Kenoyer explains.
KELLY KENOYER, BYLINE: For tourists, coastal North Carolina is a paradise, and that's the case for tiny little eastern mud snails, too. But instead of white sandy beaches, these tiny gastropods love the brackish water and muck of the estuaries.
BYRON TOOTHMAN: They are little omnivorous detritivores. They will eat anything that can fit in their little mouths.
KENOYER: That's Byron Toothman, coastal biologist speaking at one of his primary research sites, Zeke's Island Reserve. He's studying these snails to see how they've been impacted by an invasive species, Gracilaria vermiculophylla. It looks like a black tangle of witch's hair, long strands that branch off each other.
Toothman says it's a macroalgae from the Northwest Pacific, and it's been found in marshes and estuaries of the Atlantic, from Georgia to New Hampshire.
TOOTHMAN: The macroalgae will wash up against the shore and get entangled in the shoots of the grasses.
KENOYER: The algae mats agitate and weaken the structure of the sediment under the grass, and that causes it to break off in big chunks, says coastal scientist Mariko Polk.
MARIKO POLK: That loss of sediment can result in both vertical - so up and down - and horizontal - side-to-side - erosion of that area.
KENOYER: That leaves behind this extra mucky mud where the grass and the mat used to be. It's easy to get stuck in and fills up with more invasive algae.
(SOUNDBITE OF WATER SPLASHING)
TOOTHMAN: But this also gets slippery.
KENOYER: I'm kind of - not going to lie - enjoying how goopy it is (laughter).
TOOTHMAN: It's interesting.
KENOYER: Toothman discovered something else unusual, though. Those mats have a significant impact on the estuary's mercury cycle. You see, there are tiny microbes under the surface of the sediment that thrive in low oxygen conditions. One of the things they do is create methylmercury.
TOOTHMAN: And that's the form of mercury that really bioaccumulates up through the food chain.
KENOYER: There's always methylmercury under the sediment. It's a natural part of the ecosystem, and it's OK if it stays there. But this algae creates its own low-oxygen environment for these microbes above the surface of the sediment. Toothman thought that might be a problem, so he decided to investigate, using those little mud snails that stay in one spot and love to eat everything.
TOOTHMAN: Maybe I can look for mercury in these, and if they're accumulating the mercury from their environment, maybe they will tell me whether there's more mercury associated with these algae mats. And, in fact, they told me just that.
KENOYER: Toothman compared snails that lived far away from the mats to those that lived on them.
TOOTHMAN: On average, it's about two to three times as much mercury, and we found similar patterns in other organisms, like shrimp and oysters.
KENOYER: Toothman says that might have an impact on seafood humans consume. But to find out, he and other researchers will need to do more studies further up the food chain.
For NPR, I'm Kelly Kenoyer in Wilmington, North Carolina. Transcript provided by NPR, Copyright NPR.
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