What happens when millions – or billions – of sea animals die on one day?

The heat dome' over the Pacific north-west brought unprecedented death to sealife. And the effects will be felt for years to come

As a marine biologist who has studied the effects of extreme weather events for decades, I expected it would be bad. The heat dome" brought record high air temperatures to the Pacific north-west, and for the plants and animals living along our extensive coastlines the late June timing could not have been worse. The scorching heatwave coincided with some of the lowest daytime tides of the year, leaving tidal lands exposed to hot air and sun for hours during the hottest part of the day, several days in a row.

And bad it was. In the days immediately after the historic heatwave, I visited shorelines that looked and smelled like death. Mussel, oyster and clam shells open wide with rotting tissue exposed, snails and chitons no longer able to cling to the rock, kelp and surfgrass bleached white and sloughing off dead tissue. Similar scenes were reported throughout the Salish Sea of Washington and British Columbia by scientists, shellfish growers and the general public, with mortality estimates ranging from millions to billions of individuals. We've never seen anything quite like this before.