Oysters flourish, even in dirty water

Three million oysters were planted on a bed of granite by Fort Carroll in April 2017 , just outside the Baltimore Harbor. 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.

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