For a long time now, marine animals have been known to consume plastic debris due to the fact that it might look like prey. However, a recent study by Duke University of plastic ingestion by corals suggests there are chances that it may be an additional reason for the potentially harmful behaviour. Visual cues, such as a resemblance to prey, don’t factor into the appeal, the researchers noted, because corals have no eyes.
Plain plastic, scientists noted, tastes good thus the consumption. During the experiments, it was found that corals ate all types of plastics but preferred unfouled microplastics by a threefold difference over microplastics covered in bacteria. Any one or even a combination of chemical additives exist on plastic when it emerges from the factory and it is likely that it acted as a stimulant that makes it appealing to corals.
However, more research is required to identify the specific additives that make the plastic tasty to corals and determine if the same chemicals act as feeding stimulants to other marine species. Microplastics, tiny pieces of weathered plastic less than 5 mm in diameter, began accumulating in the oceans four decades ago and are now ubiquitous in the marine environment. And they pose a major threat to foraging sea animals, including many species of birds, turtles, fish, marine mammals and invertebrates.
Plastic can lead to intestinal blockages and create a false sense of fullness or reduce energy reserves in animals that consume it. The study also noted that around eight per cent plastic that coral polyps ingested was still stuck in their guts after 24 hours. It can also leach hundreds of chemical compounds into their bodies and the surrounding environment. The biological effects of most of these compounds are still unknown, but some, such as phthalates, are confirmed environmental estrogens and androgens – hormones that affect sex determination.
In another experiment, scientists put groups of coral into separate feeding chambers. Each group was offered the same amount of “food” — weathered plastics — for 30 minutes but some groups got only particles of unfouled microplastics while others got particles of weathered microplastics fouled with a bacterial bio-film. This experiment verified the corals consumed eat both types of plastic but preferred the clean type by a three-to-one margin.