In a recent study, scientists have discovered that some wild coral are feeding on tiny shreds of plastic trash. What’s worse is, they are actually preferring these ‘microplastics’ over their natural food—even when the plastic is carrying fatal bacteria. This is frightening because coral reefs are home to some of our planet’s most biodiverse ocean regions, sustaining over 25% of marine life.
Plastic degradation takes up to 500-1,000 years. Which means, nearly all plastic created still exists on Earth, often weathered down to smaller pieces less than 5 millimeters long. Lead author of the study and coral biologist Randi Rotjan of Boston University previously discovered microplastics on the surface of seagrass, yet she was still surprised with her team’s recent findings. The study was published in the journal Proceedings of the Royal Society B: Biological Sciences.
Rotjan said:
I never expected to find so many microplastics per polyp – to me, that was a big surprise. To our knowledge, this is the first report of microplastics accumulating in wild corals, though several other studies have shown coral consumption of microplastics in the laboratory.
When Rotjan first started working in marine ecosystems, she didn’t expect to be focusing on plastics. She was excited about studying corals and wanted to have conversations with nature.
Rotjan said:
Plastics keep interrupting the conversation, and it’s hard to ignore. You pick your ecosystem, you pick your organism, and you are most likely going to find microplastics.
The team collected colonies of northern star coral off the coast of Rhode Island and exposed them to either microplastics, brine shrimp eggs, both, or microbeads coated in bacteria. Then they took the creatures out, cut them open, and inspected their stomach contents. All of the coral had microplastics in their guts, with an average of 112 pieces per polyp. More than 73% of the total were plastics in the shape of fibers, followed by round particles at 15%.
Overall, the coral consumed almost double the number of microbeads as brine shrimp eggs, providing them with no nutritional value. The team suggests that there is a high, repetitive energetic cost to eating microplastics, but more research needs to be done on the effects to know exactly.
In the next phase of the study, the team coated microplastics in bacteria and released them into the corals’ chambers. After two days, the polyps spit the plastic back out but unfortunately, some bacteria remained inside them. All coral polyps that ate the bacteria-laced microbeads died within two weeks.
Co-author of the study, Koty Sharp of Roger Williams University said:
Nearly every surface in the ocean is coated with microbes, but bacterial communities on microplastics are different. In fact, they are so different that researchers have assigned a new word for them – the ‘plastisphere’. We are barely getting to know the plastisphere, and we know almost nothing about the fate of the plastisphere in the environment.
In 2015, the US banned microbeads, but that doesn’t mean they have vanished from the Earth. Plastics have been found everywhere, from tall mountain peaks and in the dark depths of the ocean to remote islands and even in the food that we eat or the water that we drink. Can you believe it? It is actually estimated that around 4.8 to 12.7 million tons of plastics end up in Earth’s oceans every year!
Rotjan said:
I hope people are inspired to make the necessary changes to clean up our world. It won’t be easy, but we have to do it. I think we all, collectively, suffer from the delusion that when we do something in a human setting – be it use plastics or release CO2 or any other action – it only affects humans. But in reality, our actions are impacting all of the citizens of Earth – all organisms and ecosystems.
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