Townsville, Australia — Plastics waste is triggering disease outbreaks in coral reefs in the Asia-Pacific region, according to a new study.
Lead author Joleah Lamb said the study examined more than 120,000 corals, both plastics-free and with plastics present, on 159 reefs in waters off Indonesia, Australia, Myanmar and Thailand.
"We found the chance of disease increased from 4 percent to 89 percent when corals are in contact with plastic. We don't know the exact mechanisms, but plastics make ideal vessels for colonizing microscopic organisms that could trigger disease if they come into contact with corals," Lamb said.
"For example, plastic items such as those commonly made of polypropylene, such as bottle caps and toothbrushes, have been shown to become heavily inhabited by bacteria that are associated with a globally devastating group of coral diseases known as white syndromes."
Lamb is affiliated with the ARC Centre of Excellence for Coral Reef Studies at James Cook University in Townsville, and is a post-doctoral research fellow at Cornell University.
"We estimate there are 11.1 billion plastic items on coral reefs across the Asia-Pacific [region] and forecast this to increase by 40 percent within seven years. That equates to an estimated 15.7 billion plastic items on coral reefs across the Asia-Pacific by 2025," Lamb said.
The study, published in the Jan. 26 edition of Science, said more than 275 million people rely on coral reefs for food, coastal protection and tourism income, and the reefs have "cultural importance."
"Our study indicates decreasing levels of plastic debris entering the ocean by improving waste management infrastructure is critical for reducing the amount of debris on coral reefs and the associated risk of disease and structural damage," the authors said.
The number of plastic items observed on each reef varied significantly. The most was on Indonesian reefs and the least in Australian waters.
The study, which the authors say is the first to examine the influence of plastic waste on disease risk in a marine organism, involved visual examinations 124,884 reef-building corals for signs of tissue loss characteristic of active disease lesions.
The study said human population size in coastal regions and the quality of waste management systems determine which countries contribute the greatest plastic loads entering the ocean, given that an estimated 80 percent of marine plastics originate from land.
The authors said their current estimate of 11.1 billion items of plastic on coral reefs across the Asia-Pacific region is likely underestimated because China and Singapore were not within the study area.
The study identified three key diseases associated with rapid coral mortality that increased markedly when plastics debris was in contact with coral tissues: skeletal eroding band disease, with an increased likelihood of 24 percent; white syndromes, up 17 percent; and black band disease up 5 percent.
The visual examinations were conducted from 2011 to 2014.