It's disturbing that sea creatures eat plastic not by accident, but because they like the taste.
For years, scientists thought that marine animals eat plastic by accident. There is so much of it in the water and it's hard to differentiate it from real food, so it ends up getting eaten. But now research is showing that marine animals actually like the taste of plastic, adding a worrisome element to the pollution problem.
Some research has been done on fish (we covered that in September), but now a recent study out of Duke University and published in the Marine Pollution Bulletin looks at coral's surprising preference for raw plastic. Scientists fed plastic micro-fragments and sand to coral polyps in a laboratory. They did this by dropping the piece near the coral and watching its reaction. From the Washington Post:
"If the sand came near their mouths, the animals used tiny hairs covering their body to brush themselves clean. But if a piece of plastic tumbled by, the corals snapped into action. They fired cellular harpoon guns, called cnidoblasts, which launched toxic barbs into the plastic particle. The corals scooped the plastic toward their mouths with their tentacles, then gobbled up the trash."
The coral ate 80 percent of the plastic offered, but ate sand only once in 10 trials, which means they can perceive a difference between the two. Said Alexander Seymour, one of the researchers, "What happens when you drop a particle of sand on a coral polyp is absolutely nothing at all."
The coral ate all plastics that were offered -- polystyrene, polyvinyl chloride, etc. Interestingly, most spat out the plastic eventually, which means they must recognize it as non-food at some point; only 8 percent retained the plastic for the full duration of the 24-hour observation period.
Coral have no eyes, which means they hunt for food using chemosensors, their version of a tongue. Essentially, they must taste something in order to decide whether it's food. When the Duke University researchers tried to alter the taste of the plastic by coating it in a microbial film, the coral were less interested; they prefer "raw plastic", eating it five times faster than the altered plastic.
Seymour says, "At least some of the hundreds of additives [in plastic] are acting as phagostimulant — a fancy word for compounds that are tasty."
This being said, the study has only looked at lab-controlled conditions; it does not know how wild coral in the ocean respond to plastic, nor does it suggest that coral are choosing plastic over real food. There are many other challenges that coral face these days that are arguably more dangerous, from bleaching and acidification to dynamite fishing.
Nevertheless, it's a disturbing reminder of the enormous impact our disposable consumer culture has on the natural world and how it can manifest in ways we do not expect.