The good news, as reported by the New York Times, is that 11.2 million juvenile oysters have been added in the past six months to a section of the Hudson River off the coast of Lower Manhattan, where they are helping to filter the water and creating habitats for other marine life.

Oysters are natural filter feeders. They feed by pumping water through their gills, trapping particles of food as well as nutrients, suspended sediments and other contaminants. In doing so, oysters help keep the water clean and clear for underwater grasses and other aquatic life.

If they grow big enough, the oyster reefs can even play a role in dissipating wave energy, helping to protect the city’s shorelines from storm surges and flooding in extreme weather.

With 220,000 acres of oyster reefs, New York harbor was once one of the world’s great oyster capitals, exporting millions of them across the country and around the globe. By the turn of the 20th century, however, overharvesting and pollution decimated the oyster reefs and in 1927, the last commercial oyster bed closed.

If the newly seeded oysters are the good news, the bad news is that the oysters can’t do it all by themselves. The new oysters in the harbor won’t be safe for human consumption for the foreseeable future, as long a New York City’s antiquated sewage system keeps dumping raw sewage in the harbor every time it rains. 

As little as one-twentieth of an inch of rain can overload the system. The culprit is an outmoded sewer system, which combines sewage from buildings with dirty stormwater from streets. More than 27 billion gallons of raw sewage and polluted stormwater discharge out of 460 combined sewage overflows (“CSOs”) into New York Harbor alone each year. Oysters may be great filter feeders but they can not disinfect raw sewage. 

In September, the remnants of Hurricane Ida triggered the release of what has been described as a “sewage bomb” from the combined sewage overflows in Newtown Creek off New York’s East River.  

 The results of sampling after the storm showed that most of Newtown Creek had maxed out the testing technology. The proportion of fecal matter was about 240 times higher than what’s considered safe for swimming.

Recently in Maryland, at least 24 people fell ill after consuming Chesapeake Bay oysters that were contaminated by raw sewage.

Heavy metal pollutants and industrial chemicals in the harbor are also beyond the oysters’ ability to clean up.

The New York Times reports that the $1.5 million oyster seeding project was designed by the Hudson River Park Trust, the New York State Department of Environmental Conservation and the engineering firm Moffatt and Nichol, using state funding.

The “seeded” oysters came from the Billion Oyster Project, a nonprofit with a mission to make its name a reality in New York Harbor by 2035. The group says it has already restored 75 million oysters to the area since its founding in 2014.

The millions of new oysters planted in the harbor are indeed very good news. Unfortunately, as long as New York CIty’s obsolete combined sewage and drain water system keeps dumping thousands of tons of raw sewage into the harbor, the oysters can only do so much.