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Oysters successfully reproducing in the Patapsco River, Chesapeake Bay Foundation finds

On a man-made reef built to help Chesapeake Bay oysters recover in the Patapsco River, nature is taking over. Researchers have found signs of new life among the mollusks.

In a semi-annual checkup of the reef next to Fort Carroll and the Francis Scott Key Bridge, the Chesapeake Bay Foundation found two spat — the name for oyster larvae that have attached themselves to the shells of other bivalves.

It may not sound like much given that the bay’s oyster population is less than 1 percent of its precolonial size.

But it’s an important step, said Allison Colden, Maryland fisheries scientist for the foundation. And it’s an especially promising one amid fears that the species might have suffered during a record year of precipitation.

Three million oysters were planted on a bed of granite by Fort Carroll in April 2017 through a collaboration that included the bay foundation, Maryland Port Administration and Maryland Environmental Service. At the time, it wasn’t clear how they would fare given poor water quality in and around the Baltimore harbor.

A survey earlier this year showed the reef was “flourishing” and supporting other species of aquatic life. But it didn’t reveal any signs of natural reproduction.

That doesn’t mean the oysters weren’t spawning, Colden said. But now there is proof that they are.

Oysters rely on salty water to grow and spawn, but biologists and watermen worry that record amounts of precipitation this year in and around Baltimore could have stunted the mollusks. The Baltimore reef is at least anecdotal evidence that the species has withstood that challenge.

Of the nearly 900 oyster samples the researchers collected from the bottom (and eventually put back there), 18 percent were dead, Colden said. That is about on par with what the researchers measured around the reef earlier this year, before all the rain.

But there were some indications all the fresh water has affected oysters in some ways.

They grew only about half an inch, on average, over the summer, less than would be expected or hoped for under normal conditions. The median size of oysters on the reef is just larger than 2 inches, Colden said.

And they were covered by a layer of dirt, which was likely washed in with the rain and also came downriver after the removal of the Bloede Dam upstream, she said. They are still resilient, though.

“They’re still sticking up out of that silt and mud and they’re doing pretty well,” Colden said.

The bay foundation plans to plant another 2 million oysters on the reef this spring.

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