From Estuary News:
West Coast salmon and steelhead populations have declined steeply in the past century – a plight that biologists have primarily blamed on habitat loss. Dams, for instance, block adult fish’s access to historic spawning grounds, and juvenile survival is impacted by streamside development and water diversions.
Now, it turns out, microplastic pollution may be a much bigger factor than anyone knew just several years ago.
In 2019, scientists with the San Francisco Estuary Institute and the Los Angeles-based nonprofit 5 Gyres published findings indicating that car tire particles are one of the most prevalent forms of microplastic pollution flowing into San Francisco Bay. Then, in 2020, a team of West Coast scientists discovered that a chemical in these particles is extremely toxic to coho salmon at miniscule concentrations, apparently responsible for abrupt die-offs of adult fish observed over many years in Puget Sound streams. The researchers published their results in the journal Science.