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Is plastic trash making coral reefs sick?

Plastic can be bad news for marine life. Seabirds and turtles will starve if they eat too many bags or six pack rings, and whales can get fatally snared in fishing gear. Now, another charismatic inhabitant of the oceans may be in danger. A new survey shows for the first time that plastic trash hikes the risk of diseases for coral reefs. Between 2011 and 2014, a team of researchers surveyed 159 reefs near Myanmar, Thailand, Indonesia, and Australia. They examined the health of more than 124,000 corals on these reefs and also checked to see whether they were hosting any pieces of plastic larger than 0.5 centimeters. Corals without any plastic had a 4% chance of being diseased, but the presence of plastic raised the risk to 89%, they report today in Science. This was true for three of the six most common diseases: skeletal eroding disease, white syndrome, and black band disease, all of which can quickly kill coral. The team has not demonstrated that plastic causes any of these diseases, but they point to possible mechanisms. Plastic trash can carry pathogens and hard debris might wound corals, triggering infection. And if plastic debris blocks sunlight, it could lead to low-oxygen conditions that promote the growth of disease-causing bacteria.