BC’s pink sea urchins are moving to shallower waters thanks to climate change

VANCOUVER – Pink sea urchins off the coast of Vancouver Island are spreading to shallower waters, which researchers say is an indication of how rapidly climate change is affecting ocean life.

Researchers from Memorial University, Ocean Networks Canada and the University of Victoria found that the sea urchins, which live up to 400 meters below the sea surface, are expanding their populations into shallower water at an average rate of 3.5 meters per year as the Warming of the ocean reduces oxygen levels and food sources at shallower depths.

Study co-author Rylan Command said that thermal domes and heat waves are becoming more common and that understanding how the ocean responds to these changes can have a direct impact on people.

The movement of pink sea urchins over time, for example, could upset the balance with other sea creatures and cause them to replace other species like the red sea urchin harvested in fisheries, he said.

“It’s almost like an indicator that things are changing fast and that’s important to people because that’s going to affect us, too,” he said.

The researchers looked at 14 years of data, including before, during and after the ocean heatwave known as “The Blob,” which lasted in the Pacific Ocean between 2013 and 2016.

They used data from both an Ocean Networks Canada observatory and the Federal Fisheries and Oceans Trawl Survey to gather information from about 400 meters deep, covering an area of ​​760 square kilometers.

“We were able to get a holistic picture of how everything is changing. I think this kind of data combination is really important and really useful,” Command said.

Study co-author Fabio De Leo, who works at Oceans Network Canada, said warming from The Blob destroyed much of the kelp that the sea urchins eat, leading to a dramatic decline in their populations.

“The kelp forests felt the ocean heatwave pretty badly. So that’s essentially one of the main foods for the pink sea urchin,” he said.

The researchers say the higher-than-average surface temperatures also disrupted the ocean process known as “upwelling,” which sees nutrient-rich water rushing to the surface from deeper depths and potentially affecting where the sea urchins find food.

The BC research aligns with similar work done in California in 2017, which found that pink sea urchins also sought out shallower waters in that region.

De Leo said it’s important for monitoring the area to have data that spans more than a decade.

“We need to know how biodiversity and marine communities are changing over time in order to adapt and make plans,” he said.

This report from The Canadian Press was first published on February 7, 2023.

Ashley Joannou, The Canadian Press

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