Study: Corals Eat Plastic Debris Because It Tastes Good To Them
Rather than it simply being the case that corals eat tiny plastic debris because they mistake it for prey, chemical additives in the plastic may be acting as a feeding stimulant — making the plastic “taste good” — according to a new study from Duke University. As a reminder here, corals have no eyes, and aren’t thought to possess much of a visual system.
“A white fleck of plastic is engulfed by a coral polyp.” Photo by Alex Seymour, Duke Univ.
“Corals in our experiments ate all types of plastics but preferred unfouled microplastics by a threefold difference over microplastics covered in bacteria,” noted Austin S Allen, a PhD student at Duke’s Nicholas School of the Environment. “This suggests the plastic itself contains something that makes it tasty.”
“When plastic comes from the factory, it has hundreds of chemical additives on it. Any one of these chemicals or a combination of them could be acting as a stimulant that makes plastic appealing to corals,” explained Alexander C Seymour, a geographic information systems (GIS) analyst at Duke’s Marine Robotics and Remote Sensing Center, and study co-author.
This is a problem as plastic is essentially indigestible, and thus the ingestion of it leads to reduced energy availability and general health and wellbeing, and can also cause intestinal blockages.
“About eight percent of the plastic that coral polyps in our study ingested was still stuck in their guts after 24 hours,” noted Allen. “We found that the corals ate all of the plastic types we offered and mostly ignored sand.”
An accompanying problem is the chemical pollution that invariably accompanies the ingestion of plastics — the effects of most of the chemicals found in plastics on human and animal health remains an unknown.
The press release provides more: “Allen and Seymour conducted their two-part study using corals collected from waters off the North Carolina coast. In their first experiment, they offered small amounts of eight different types of microplastics to the corals to see if the animals would eat the bite-sized bits versus other similarly-sized items offered to them, such as clean sand.
“In the second experiment, they put groups of coral into separate feeding chambers. Each group was offered the same amount of ‘food’ — weathered plastics — for a 30-minute period, but some groups got only particles of unfouled microplastics while others got only particles of weathered microplastics fouled with a bacterial biofilm. This experiment verified that the corals would eat both types of plastic, but preferred the clean type by a three-to-one margin.”
As a reminder here, micro-plastics are now ubiquitous in the environment — with even our drinking water now being host to significant amounts of the stuff. The oceans are now literally filled with it, which poses a number of unpleasant questions about the future health of the ocean’s ecosystems.
The new study was published in the online edition of the journal Marine Pollution Bulletin.
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