Credit Alexander Seymour and Austin Allen
The ocean is full of plastic. Eight million tons are dumped in the seas every year. Plastic bags have been found in the guts of dead sea turtles, which mistake them for jellyfish. More than 200 species have been documented eating plastic, which looks colorful and edible but can kill them.
In lab experiments, even tiny corals, the organisms that make up reefs, have been observed nibbling on a confetti of broken down plastic fragments similar to what swirls through the depths. But they aren’t just eating whatever floats by. Instead, according to a new study in Marine Pollution Bulletin, some of the chemicals infused in the plastic may actually taste like food to the corals.
It isn’t yet clear how much plastic is consumed by corals in the wild, or what harm it might do to these important marine organisms, which are already threatened by environmental dangers like warming seas and pollution. But understanding why plastic might appeal to them is important, especially because some particles appear to get stuck in the corals, potentially disrupting their digestive process.
Hundreds of chemicals are mixed into plastics to achieve certain textures or other characteristics. Because the corals sense the presence of food with receptors, it would not be all that surprising if some chemical additives mimicked substances that set off the corals’ appetites, suggested Alexander Seymour and Austin Allen, who were both graduate students at Duke University when they led this study.
In their experiment, the researchers offered corals collected from North Carolina’s coastal waters two different kinds of plastic to see what would be more popular: older plastic, weathered in seawater and covered with a thin layer of bacteria, or plastic fresh from the factory. The corals seemed to prefer the newer plastic, ingesting more of it than the older shards.
The difference between the consumption of new and old plastic could come down to the concentrations of additive chemicals. Perhaps the microbes on weathered plastic kept those added compounds from reaching the corals as swiftly. Or maybe the microbes produced substances that kept the corals from eating them as quickly.
Daniel Rittschof, the pair’s adviser, and other members of the lab are now working to verify whether specific substances in plastic are tasty to marine invertebrates. Finding out what these are and how they work could have far-reaching implications.