By Alex DeMetrick

BALTIMORE (WJZ) —  Scientists knew oysters were good for the bay but they never knew how good until now.

Alex DeMetrick reports for an animal that doesn’t move, it works pretty hard.

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Here’s what science already knew:

“These oysters, they filter the water. One adult oyster can filter up to 50 gallons of water a day, so you think of all these millions of oysters and they’re just a factory for clearing the water,” said Tom Zolper, Chesapeake Bay Foundation.

That’s a big reason millions of dollars are being spent to spread old shells containing baby oysters onto natural and artificial reefs.

What wasn’t known until now is how effective they are at filtering nitrogen out of the water.

“We found it was considerably higher than we ever thought be,” said Jeff Cornwell, University of Maryland Center for Environmental Science.

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The University of Maryland Center for Environmental Science took part in the study, focusing on nitrogen because it feeds algae blooms that created dead zones.

“We need to take out about half a million pounds of nitrogen here in the Choptank River. If we could plant oysters on 23 percent of the bottom you can grow them, we would accomplish that goal,” Cornwell said.

It turns out oyster reefs work like sewage treatment plants, which lure bacteria to convert nitrogen into a gas.

“It’s a harmless gas. It makes up 80 percent of our atmosphere,” said Mike Owens.

Fixing numbers to what’s happening to an underwater oyster reef isn’t easy.

“Being able to bring back an intact section of oyster reef and bring it into the lab and try to make measurements on it is a very challenging process,” Owens said.

That’s paid off in hard numbers about what could be gained down here if oyster numbers can be increased.

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Oysters aren’t alone down there. The study also found a healthy reef supports life for 24,000 other organisms per square meter.