Plastic ocean litter boosts lethal infections in corals

A Nike logo is clearly visible on an item lodged into a coral reef

A Nike logo is clearly visible on an item lodged into a coral reef Credit James Cook University

Besides plastic waste damaging the corals - tiny invertebrates whose calcium carbonate skeletons build up reef structures - another threat comes from the way the detritus can carry diseases across open seas.

"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.

The researchers estimate the increased chance of infection on the reefs affected could be as high as 89 per cent, in some cases. Every year, millions of tons of waste end up in the oceans, where they remain indefinitely.

The plastic may stress the corals by blocking light and oxygen from reaching them or cut into the coral's flesh or rub against it, creating a wound that bacteria can get in.

Kelly, now a PhD student at Carleton University in Ottawa, participated in the Australian surveys while doing her master's degree at James Cooke University in Townsville, Queensland: "I didn't mind one bit".

Coral reefs are already being assailed by catastrophic "bleaching" events along with over-fishing and attacks by ravenous starfish but now man-made plastics are being highlighted as threat because they can introduce disease into the delicate eco-systems.

Sadly, plastic waste, including bags, straws, small toys, fast food packaging, bottles, and more, comprise a massive problem for the environment. Kelly says after seeing the findings of the study she co-authored, she no longer uses plastic straws and shopping bags. The study, published Thursday in the journal Science, said the likelihood of disease skyrockets from 4 percent to almost 90 percent when coral comes in contact with plastic.

Coral reefs are productive habitats in the middle of nutrient-poor waters, Harvell said.

This allows bacteria and viruses to gain hold on the coral, with spikey coral more likely to snag any plastic rubbish. The presence of plastics seemed especially to aggravate some common coral afflictions, such as skeletal eroding band disease.

"Those pathogens eat the tissue", said Joleah Lamb, a postdoctoral researcher at Cornell University and lead author of.

"Any compromise like that is going to make creatures more susceptible to the risks of other diseases".

"They do not present clear evidence as to whether the pathogens were transferred by the plastic - but that is certainly a possibility", he said.

Furthermore, the authors also predict that the number of plastic items entangled in coral reefs in the Asia-Pacific could increase to a staggering 15.7 billion by 2025.

In collaboration with numerous experts and underwater surveyors across Indonesia, Myanmar, Thailand and Australia, we collected data from 159 coral reefs between 2010 and 2014.

Journal Reference: Joleah B. Lamb et al.

Based on other studies, the researchers think there are a couple of ways the plastic could be causing disease. She also examined whether existing coral reef management strategies are effective for mitigating marine diseases, such as the use of marine protected areas.

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