"Those pathogens eat the tissue", said Joleah Lamb, a postdoctoral researcher at Cornell University and lead author of.
A new study of more than 100,000 reef-building corals in the Asia-Pacific region found that plastic on reefs promotes "colonization by pathogens implicated in outbreaks of disease in the ocean". And that number is expected to rise 40% within the next 7 years.
"This study demonstrates that reductions in the amount of plastic waste entering the ocean will have direct benefits to coral reefs by reducing disease-associated mortality", Lamb said.
Based on how much plastic the researchers found while diving, they estimate that over 11 billion plastic items could be entangled in coral reefs in the Asia-Pacific region, home to over half the world's coral reefs. To start with, plastic in the ocean is a magnet for bacteria, including some implicated in coral diseases. Indonesia was found to be the worst offender, with the coral in Australia suffering the least - possibly due to Australia's intense clean-up and disposal efforts. The researchers assembled a database of plastic pollution on 159 reefs in Australia, Indonesia, Myanmar and Thailand, surveying about 12,000 square meters of reef.
"Laboratory studies have shown that plastic encounters can cause really subtle, chronic effects and harm, compromising the ability of organisms to grow in the normal way for example", he said.
She began collecting this data as a doctoral candidate at James Cook University in Australia.
In order to assess how much plastic there is in the reefs, global researchers surveyed more than 150 reefs for four years (from 2011 to 2014).
"Plastic items - commonly made of polypropylene, such as bottle caps and toothbrushes - have been shown to become heavily inhabited by bacteria". These reefs provide the USA around $375 billion in goods and services through fisheries, tourism, and coastal protection, and when you consider that 80 percent of this debris originates on land, curbing the problem is very much in our power. In December (2017), nearly 200 nations agreed to limit plastic pollution of the oceans, warning that it could outweigh all fish by 2030.
"There are really great studies showing how much plastic is going into the oceans and how much is floating on the surface", says Lamb, who's now a fellow at Cornell University.
Once corals are already infected, it is logistically hard to treat the resulting diseases.
Further investigations are needed to determine precisely how and why plastics make coral susceptible to different diseases. It was the idea of a graduate student, Joleah Lamb.