This popular St. John's swimming spot smells like broccoli. We asked an ecologist to find out why

Record temperatures across Newfoundland and Labrador are creating perfect swimming weather — but some residents are avoiding one popular spot in St. John's due to an unpleasant odour.

For several weeks, swimmers have complained of a stench wafting from George's Pond, a beloved feature of Signal Hill.

"It reminded me of broccoli," said Kathryn Cole, a Memorial University biology student.

Cole, a swimmer herself, is studying under assistant professor Kathryn Hargan, who specializes in ecology.

CBC Radio's St. John's Morning Show asked Hargan and Cole to test the water coming from George's Pond.

St. John's residents have swam in the pond for years, but until 2022 the city actually prohibited swimming in the pond because it was used as backup drinking water. After lifting the ban, the city erected signs advising that use of the pond is at one's own risk.

Last week, Hargan and Cole went out onto the pond in an inflatable boat to gather samples, a regular part of Hargan's work as an ecologist. 

Hargan said she looks at water quality, algae and historical conditions in bodies of water.

"Things are changing," she said. "There is climate change and there's other things that are changing in the province and around the world, and so we're trying to understand what that means for the biology of ponds and what that means potentially for drinking water quality."

Hargan examined the sample from George's Pond under a microscope in her lab at Memorial University's St. John's campus. She did find odour-causing species of algae in the sample, but said it likely isn't behind the stench at the pond.

"Most of them … cause more of a fishy smell, which isn't what's been described at George's Pond," she said.

Hargan said decomposition of algae and plant matter is likely behind the smell — potentially exasperated by hot conditions. 

"Often if you have decomposition you have sulfur and that's what creates what's more often described as a cabbage smell," she said.

Still, Hargan said a definitive answer would require regular monitoring and testing.