Foul smell in Great South Bay is from decaying invasive seaweed

The smell is so potent that it is described as rotten eggs or a sewage spill. But it is neither of those. Instead, scientists have pinpointed the source of the odor in the Great South Bay as an invasive red seaweed. The red tinge in the water is most noticeable on warmer days with a south wind but often no one even knows it is even there.

This foul phenomenon is newer to North America. And this latest outbreak on Long Island is wreaking havoc in the Great South Bay, where the seaweed thrives on high nitrogen and carbon dioxide, according to Dr. Chris Gobler, a professor at Stony Brook University.

"It originated from Japan and it's slowly spreading across the globe," Gobler said. "It likes slightly cooler temperatures, and over the summer as the bay gets warmer, it starts to decay. And come the fall, the decayed seaweed and rotted seaweed smell pretty bad."

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Aside from the smell, scientists said decaying seaweed can reduce oxygen in the water and harm sea life. In high concentrations, it can also be dangerous to breathe in.

"At high levels, rotting seaweed can release hydrogen sulfide gas and make people sick," Gobler said. 

Some ways to take action include limiting the use of fertilizer and updating your septic tank.

"Our home values, businesses, and recreational opportunities are dependent on the bay being healthy," Save the Great South Bay's Robyn Silvestri said.

Curbing pollution and sewer runoff now help make sure the bay is healthy for generations to come.