Is ocean acidification knocking the scents out of salmon?

The results of the new study don’t bode well for these fish, Williams says. Already, he notes, these fish and their ecosystems face a host of other pressures. Dams on some rivers, for instance, make it difficult for coho to return to spawn in their home streams. And even should they make it upstream to spawn, dams might kill young coho as they tried to migrate downstream to the sea. Polluted storm water flowing into Puget Sound is also proving toxic to these fish.

James Helfield agrees that the study is bad news for coho. He is a fisheries biologist at Western Washington University, in Bellingham. Helfield studies salmon ecology but was not involved in the study. “This study illustrates another way that climate change might harm salmon populations,” he says.

In many waters, salmon are more than just another fish in the sea. In the ocean, they provide essential food for other species, including seals, orcas, other fish species and, of course, people. In rivers, they have a trickle-up effect on the food web and the ecosystem. Once salmon die in those rivers, their decaying bodies add nutrients to the forest.

And what’s bad news for salmon is probably bad news for other marine species, too. In fact, says Helfield, the study’s findings are not unexpected. “Other recent studies,” he notes, “have shown that some marine fish become ‘drunk and disoriented’ when exposed to too much carbon dioxide in sea water.”