Sunflower sea star. Credit: NOAA Fisheries
A team of oceanographers and marine biologists at the Hakai Institute, working with a colleague from the Central Coast Indigenous Resource Alliance, and another from the Institute of Ocean Sciences, all in Canada, has found that the highly endangered sunflower star, a type of sea star, has found some degree of refuge in Canadian fjords (spelled fiord in Canada).
In their paper, published in the journal Proceedings of the Royal Society B, the group describes how they compared surveys of the biomass density of sunflower stars along the central British Columbia coast, both before and after the onset of sea star wasting disease (SSWD) and what they learned by doing so.
Over the past decade, the population of the sunflower star, which lives along the coast of North America, has dropped precipitously. Their global population is down 90.6% since 2013. The culprit is global warming, though indirectly. Global warming, it has been noted, has led to warmer ocean temperatures, particularly along coastlines.
Prior research has shown that SSWD prefers warmer water, which is why it has flourished, allowing it to kill so many of the sunflower stars that live along the coastline. In this new effort, the research team in Canada has found that some parts of the Canadian coastline appear to be offering a refuge of sorts.
Researchers at Hakai Institute have been conducting biomass density surveys along Canada's coast for several decades. Thus, they notice when populations of ocean creatures living there change. In this case, they noticed dramatically falling numbers of sunflower stars starting around 2013. Testing showed most of the drop was due to SSWD. But, in taking a closer look at the census numbers for the sea stars, the research team found that their density numbers appeared to be higher in fjords than in other parts of the coastline.
(A) Artistic illustration of the influence of the freshet on P. helianthoides distribution across depths.
(B) Salinity and temperature across depth for data included in figure 5, illustrating that salinity on the outer islands is all above 15 psu, and that higher temperature water in the fjords is associated with fresher water.
Credit: Proceedings of the Royal Society B: Biological Sciences (2025). DOI: 10.1098/rspb.2024.2770
Emboldened by the statistics, members of the team began diving in several of the fjords and found many more of the sunflower stars there than anywhere else. They suspect it is likely due to the cold water. Arctic outflow, they note, results in cold winds blowing across the region, which cools the water and also adds more oxygen.
The research team notes that in the summer, there is a lot of glacial runoff, dumping a lot of really cold water into the fjords. Then, because the sea stars do not like cold water, they go deeper. And that, the team suggests, may be shielding them from SSWD.
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