BROOKHAVEN, N.Y. — For all the devastation wrought by Hurricane Sandy on the New York region four years ago, there were a few places that stood out, becoming symbols of the storm.

There was the image of a roller coaster resting in the ocean off Seaside Heights, N.J. There were miles of boardwalk ripped from pilings in the Rockaways, as well as the blackened remains of 126 houses that burned to the ground there. And on Fire Island, there was a breach carved by the storm surge, which opened a passage between the ocean and the bay.

While the worst of the storm damage has been put right, the lingering scar from Hurricane Sandy remains on Fire Island. But unlike the wreckage elsewhere, the breach that cuts through the Otis Pike Fire Island High Dune Wilderness here is, increasingly, seen as something of a good thing that many people, including local officials, environmental activists and marine scientists, say should be left alone.

The reason is that the Great South Bay, which is flanked by Fire Island and Long Island’s South Shore, has become a sick patient. In the past 30 years, the bay, which once supported a robust clamming industry, has been affected by leaking septic systems and storm-water runoff containing lawn fertilizers and herbicides. The excess nitrogen spawned pervasive brown tides and algal blooms that, in turn, led to the collapse of clamming and imperiled the bay’s ecosystem.