In a study led by California Sea Grant Extension Specialist Theresa Talley, researchers found that nearly a quarter of fish sampled from a creek that flows into San Diego Bay contain microplastics. This work, which was recently published in the journal PLOS ONE, examined plastics in coastal sediments and three species of fish.
The study reveals that species’ natural history, in particular what they eat, how they feed and how those change over their lifetimes, may influence their contamination levels. This new information on how plastics travel through the environment and into fish could help add a key piece to the emerging picture of the dynamics and impacts of plastics in California’s coastal environment. To better understand the impacts and movement of plastic through an urban watershed and the fish that inhabit it, Talley and colleagues focused their study on the highly urbanized Chollas Creek. The creek flows from a densely populated area of San Diego into San Diego Bay—reported to be the second-most polluted bay in the country.
The team identified 25 categories of plastics in the sediments, including pieces of film, polystyrene, soft and hard plastic, microbeads and synthetic fibers, with the fibers and both hard and soft pieces making up 90% of fragments found on the creek bed. The fish, in contrast, seemed to consume only about half of the categories of plastic observed in the environment.
“If we want to reduce the risks that plastic pollution poses to sea life and, ultimately humans, we need to better understand the processes underlying the entry of plastics into food webs,” says Talley, “It’s no longer enough to document all the places we find plastics. If we want to develop solutions, we need a clearer understanding of how and why the plastics move through ecosystems.”
Images provided by California Sea Grant.