She made her way to the edge of the water. It smelled like putrid shellfish — cooking.

All around her, beds of mussels had popped open, dead. The heat beating down on the rocks had killed them, and she could see dead tissue between their shells.

A dead crab floated in the water, she said.

Gehman studies marine community ecology, but this was the first time she had seen anything of this “magnitude of mortality.” An estimated 1 billion small sea creatures — including mussels, clams and snails — died during the heat wave in the Salish Sea, off more than 4,000 miles of linear shore, according to marine biologist Chris Harley.

Record-breaking temperatures hit the Pacific Northwest at the end of June, with an all-time high in British Columbia of 121 degrees. British Columbia reported at least 719 people suffered “sudden and unexpected deaths,” three times more than what would normally occur in the province during a seven-day period.

Lisa Lapointe, the province’s chief coroner, said in a statement last week that the extreme heat probably was “a significant contributing factor” in the increased number of deaths.

Harley’s research team used infrared cameras to measure temperatures on the shoreline rocks — recording some readings as high as 122 degrees.

With mechanisms to keep from drying out, mussels are able to withstand high temperatures. They hold water inside their shell and close up on land, when exposed by tides. They grow in beds, which provide a thermal buffer. But the record heat was just too much.