Microplastics and a widely used pesticide are helping kill off sea star populations in Washington state’s Puget Sound, new research shows.
The findings come as researchers look into what has caused a mass sunflower sea star die off in the region. Though it’s not yet clear whether the toxic substances are at the die off’s root, the study found that microplastics and the pesticide have detrimental impacts on young sea stars, which could prevent the population from rebounding.
Finding that the two pollutants cause mortality in sea stars is “not good”, said Allie Tissot, a doctoral candidate at Portland State University and co-author.
“Their populations are really low and there are only so many on the coast right now,” Tissot said. “There are so many microplastics, contaminants and chemicals that might be in their environment, so we don’t know what the full combination of effects may be.”
Sunflower sea stars in the Pacific north-west are considered endangered by some groups as wasting sea star syndrome decimates the population, creating a domino effect that is throwing off an ecological balance in the region. Too few sunflower sea stars results in the proliferation of sea urchins that consume kelp that provide a range of benefits to aquatic life along the coast, including providing shelter for young fish.
The pesticide, Imidacloprid, has been known to devastate bee populations and kill songbirds. The substance is about to be banned in the UK, but the US Environmental Protection Agency has resisted calls for a prohibition.
The study also focused on microfibers, a type of microplastic that typically comes from clothing and textiles, and is about one-fifth the size of a human hair. Microfibers are a toxic material that can also carry dangerous chemicals. Laundry machines are thought to be the main source of microfibers because the pieces shed from clothing during wash cycles.
Among other issues, the pesticide caused gut malformations and prevented the stars’ stomachs from growing, which ultimately killed them. Imidacloprid, which targets mosquitos, works by preventing the insects’ stomachs from growing, so it is not entirely surprising that it has the same impact on other organisms.
The microfibers also seemed to accelerate growth, a response likely stemming from the stars being unable to get enough nutrients. The contaminants may not be causing wasting sea star syndrome, Tissot said, but it could be preventing the population from recovering.
The findings also caused alarm because researchers only looked at the effects of two common contaminants – sea stars are exposed to a wide range of toxins that could impact their health.
However, help may be on the way. The state senate in Oregon, Washington’s southern neighbor, is considering a bill that would require microplastic filters in new washing machines sold in the state.
Meanwhile, the federal government has proposed listing the sunflower sea star as a threatened species under the Endangered Species Act. That action would trigger a prohibition on spreading the pesticide in the region.
“The least we can do is to reduce additional stressors on marine ecosystems, such as pesticide inputs and plastic contamination,” said Jason Hodin, a study co-author and University of Washington researcher.