I'll let Goldstein, writing about her work in Deep Sea News, take it from here:

Eventually I found myself in the lab dissecting barnacles in order to identify them. As I sat there, I thought “Well, I’m working on these barnacles anyway – wonder what they’re eating?” So I pulled out the intestine of the barnacle I was working on, cut it open, and a bright blue piece of plastic popped out.

Yep. Blue plastic, inside the creature's intestine. "I reached into my jar o’ dead barnacles and dissected a few more," Goldstein continues, "and found plastic in their guts as well."

Goldstein and a colleague, Deborah Goodwin, ultimately dissected 385 barnacles. And about a third of them (33.5 percent) had tiny pieces of plastic in their guts. Most of those organisms had eaten "just a few particles," Goldstein notes, "but we found a few that were absolutely filled with plastic, to a maximum of 30 particles, which is a lot of plastic in an animal that is just a couple inches long."

They analyzed the plastic, as well, and determined that it was generally representative of the microscopic plastic that floats on the ocean surface within the gyre. (It was a combination, the pair note in the paper they published about the finding, of polyethylene, polypropylene, and, less commonly, polystyrene.) Which would suggest, Goldstein notes, that "the barnacles are probably just grabbing whatever they come across and shoving it into their mouths."

So this is where our trash—our soda bottles, our coffee cups, our kids-meal toys—can end up when it breaks down: inside the intestines of hungry, and unsuspecting, sea creatures. In some sense, Goldstein notes, it's entirely logical that gooseneck barnacles would be eating plastic. "They are really hardy, able to live on nearly any floating surface from buoys to turtles, so they’re very common in the high-plastic areas of the gyre." Plus, "they live right at the surface, where tiny pieces of buoyant plastic float." Not to mention the fact that "they’re extremely non-picky eaters that will shove anything they can grab into their mouth."

Goldstein notes that the amount of plastic found in her samples is likely not fully representative of the amount of plastic the barnacles actually consume. They probably eat much more plastic than their preserved digestive tracks indicate. ("Barnacles are perfectly capable of pooping out plastic—I observed plastic packaged up in fecal pellets, ready to be excreted the next time the barnacle had access to a couple minutes and a magazine—so it is very likely that more barnacles are eating plastic than we were able to measure.") And one piece of good news, Goldstein and Goodwin note in their paper, is that the plastic particles didn't seem to block the barnacles' stomachs or intestines.