NORTH KINGSTOWN, R.I. (WPRI) — If you go to the upper pond of the Narrow River right now, you might catch a whiff of rotten eggs. Veronica Berounsky, president of the Narrow River Preservation Association, said it's nothing to be concerned about. "It's a natural occurrence, so don't be alarmed," said Berounsky, who also works as a coastal ecologist at the University of Rhode Island's Graduate School of Oceanography. Berounsky said the river is actually an estuary, which is a place where salt water from the ocean meets fresh water from the Gilbert Stuart Stream. TARGET 12: Climate change pushing some marine species out of Narragansett Bay The upper pond and lower pond are deep basins that are about 42 and 60 feet deep respectively. Berounsky said that, at the bottom of those basins, there is an oxygen-free zone rich in sulfur. This layer recently "overturned," ending up on the surface, according to Berounsky. "I think the trigger for this one was the king tides that we had," she explained. "We have had a dry fall. Less fresh water is coming into the system ... and so you've got more sea water coming up, in particular, with the king tides." The upper pond of the Narrow River has overturned, making the water appear milky. (Courtesy: Steve Carey) Berounsky explained that, when the dense sea water goes to the bottom of the basin, it pushes up the sulfur-rich water sitting at the bottom. The layers of water with varying oxygen counts then mix together and ventilate so that gas levels can replenish throughout. As a result, she said the water looks milky and the sulfur that's closer to the surface gives off the smell of rotten eggs. Though some of the marine life in the water won't survive, but Berounsky said the ecosystem will recover. Berounsky said it's still safe to boat, fish or kayak in the Narrow River, but she doesn't recommend swimming since the sulfur can dry out your skin. The natural event is highly unique and only happens once every 10-15 years, according to Berounsky. She said the last time an overturn lasted more than a day was back in 2007, when it stuck around for six weeks. Berounsky doesn't know when the overturn will stop, but she said everyone should try and see it for themselves while they can. "There aren't a lot of places in the world that have conditions like this, so it's a pretty unique thing," she said. "The pictures are cool, but to actually see it in person is really pretty cool." Close Thanks for signing up! Watch for us in your inbox. Subscribe Now Ocean, Bay & Beach Report SIGN UP NOW