There are tens of thousands of seals on Cape Cod and the Islands, and everyone seems to have an opinion about them. Some see them as an adorable tourist attraction that helps the ecosystem. But to others, they’re Public Enemy No. 1 — a messy, fish-eating shark magnet that needs to be culled. “We don’t know what other cascading effects seals will have,” says Joe Roman. “I think there’s good reason to believe that they’re going to change the nutrient dynamics, but they may also have new surprising roles. And that’s the fun part about science.” Listen to the story on WBUR.