Jan 25, 2018 - Energy & Environment

Coral reefs endangered by massive plastic pollution

Photo of coral off coast of Indonesia with pollution, including a piece of something with a Nike emblem, causing white syndrome coral disease

Plastic pollution, such as this Nike logo, helps foster certain diseases like white syndrome coral disease seen here. Photo: Joleah Lamb / Cornell University

The billions of pieces of plastic waste hovering in the oceans of the Asia-Pacific region are causing a 20-fold increased risk of diseases deadly to coral reefs, according to a new study published in Science Thursday.

Why it matters: The estimated 11.1 billion plastic items lodged around the Asia-Pacific coral reefs boost the risk of coral contracting skeletal eroding band disease, white syndromes, and black band disease, they found. About 275 million people in the region rely on the reefs for food, tourism, marine biodiversity, and coastal protection.

"Plastic is a triple whammy for coral infections — it abrades and cuts open the skin of the coral, and then can convey pathogenic microorganisms. [It] shades and cuts off water flow,"  study author C. Drew Harvell tells Axios.

What they did: Over multiple years, the scientists surveyed coral health on 159 reefs from Australia, Myanmar, Thailand, and Indonesia — saying this represents more than half of all global coral reefs and 73% of human populations living near the coast. At each site, they identified and surveyed a 30-foot-long area of coral habitat (called a transect line), with 3 transects at each site. They measured the level of plastic pollution and examined over 124,000 reef-building corals for diseases.

To control for the damage caused to reefs by global warming, Harvell says the surveys were carried out at a time of year when the corals weren't bleached by warm water. "The bad thing is that we expect plastic will make corals much less resilient to warming events and prevent them for recovering," says Harvell, an ecologist at Cornell University. "So it's the combination of the two stresses that is very destructive." 

What they found: The likelihood of disease in the coral rose to as high as 89% when corals were in contact with plastic — much higher than the 4% risk without the pollutants — depending on the disease and the type of coral.

The limitations: Eric Hochberg, a reef ecologist from the Bermuda Institute of Ocean Sciences who was not part of this study, says the research does a "good job raising a new concern about plastics on coral reefs," but adds that the "observed reef area cannot be considered representative of all reefs across the Asia-Pacific region."

He says some of the figures show the total area of the reefs that were visited, instead of the actual areas that were observed and measured. "This is 0.00086% and 0.00156% of the reported global and Asia-Pacific reef areas, respectively," Hochberg tells Axios.

What's next: Harvell says they estimate the level of plastic items entangled in coral reefs will grow 40% to 15.7 billion plastic pieces by 2025, unless plastic management systems are adopted globally.

"If the modeled predictions are borne out, this is yet another area where humans should work to lessen our impact on this aesthetically, culturally, and economically valuable natural resource. I think reducing the transport of plastic garbage to the ocean is an achievable goal, even for developing nations," Hochberg tells Axios.
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