11 Billion Pieces of Plastic Are Making Coral Reefs Sick

The ocean is incredibly vulnerable at the moment. Humans are producing billions of tons of plastic waste and climate change is increasing ocean temperatures. A study published Thursday in Science estimates that roughly 11.1 billion pieces of pathogen-carrying plastic are affecting coral reefs in the Pacific.

These reefs are incredibly important. They provide protection to the shoreline from crashing waves, they bring in income from tourists, and act as nurseries for fish. “Although coral reefs cover less than 1 percent of the ocean floor they are estimated to support 25 percent of marine life globally,” a spokesperson for the US Environmental Protection Agency (EPA) wrote me in an email. According to the new study, coral reefs provide $375 billion in goods and services to the US alone.

But they’re being choked by plastic. 80 percent of ocean debris originates on land—the average American citizen used 68 kilograms, or about 150 pounds, of plastic per year in 2014. In the new study, the first to look at how this plastic affects the health of coral reefs in the Pacific Ocean, researchers estimated 11.1 billion of pieces of plastic are currently entangled in Asian-Pacific coral reefs, each one increasing the likelihood of corals becoming diseased from 4 percent to 89 percent.

From 2011 to 2014, researchers from Cornell University, James Cook University in Australia, and the nonprofit Environmental Defense Fund, among others, surveyed 124,000 reef-building corals, examining them for evidence of plastic and telltale signs of six common coral diseases caused by pathogens that can float toward them on little plastic boats: skeletal eroding band, a group of diseases called white syndromes, and black band disease.

The presence of plastic on coral reefs was obvious. One-third of the reefs they surveyed had at least two plastic items per 100 square meters. In Indonesia it was especially bad, with an average of about 25.6 plastic pieces per 100 square meters, while Australia was far less affected, with an average of about 0.4 plastic pieces per 100 square meters.

“In some of the places we visited in Indonesia, the trash was knee deep on the shore, adjacent to a coral reef,” Drew Harvell, a professor of Ecology and Evolutionary Biology at Cornell and the senior scientist on the project, wrote me in an email.

The Asia-Pacific region encompasses 55.5 percent of global coral reefs and 73 percent of the human population living within 50 kilometers, or about 31 miles, of the coast. Based on the human population size in these areas and their observations of plastic, the authors estimated 11.1 billion plastic items on the region’s reefs. They also predicted that this number would balloon to 15.7 billion by 2025. Just seven years and plastic on reefs will increase by 40 percent.

Plastic waste provides an ideal surface for pathogens to stick to. Vibrio, a pathogen that consumes the symbiotic algae living in corals and is associated with the white syndromes, dominates polypropylene debris.

“Plastic is a triple whammy for increasing coral infections,” Harvell said. “It abrades and cuts open the skin of the coral and then can convey pathogenic microorganisms and shades and cuts off water flow.”

Harvell and her co-authors found that plastic increases the likelihood of disease for corals by more than a factor of 20 in all the regions surveyed, from 4.4 percent to 89.1 percent.

Plastics are eight times more likely to cause disease for more structurally complex corals. It’s harder for plastic to get caught on flatter corals (known as massive corals), so they are less prone to disease. Those unlucky massives that do get hit, though, experience a 98 percent increase in the likelihood of disease.

The future looks bleak for these organisms. “In some cases, infected corals can recover if the stress is removed. In other cases, particularly if there is another stress, like coral bleaching, the infection spreads and kills the entire coral colony,” Harvell said. With the increase in coral bleaching over the past several decades caused by climate change, corals seem even more at risk.

So what are the solutions? Maybe governmental regulation, but with the current US administration’s attitude toward the environment, that doesn’t seem likely, at least in this country. As the EPA wrote me, they recognize that “plastic products and packaging are essential materials for the modern world,” and they “do not advocate nationally for specific regulatory mandates regarding the use of plastics.”