“Shockingly high” levels of plastic contamination have been discovered in some of the most remote parts of the Chagos Marine Protected Areas – raising fears among scientists over the region’s population of reef manta rays for which Chagos has been designated a global safe haven and important feeding area.

Micro-plastics and micro-fibres linked to man made, clothing-related polymers such as polyester found in the area surpass those found in more densely populated regions such as Indonesia, with plastic concentrations reaching as critical level as 1.1 particles per cubic metre.

Published late last month in the scientific journal The Society for Conservation Biology, the study has since drawn direct attention to the scale of the micro-plastic and micro-fibre crisis, indicating that even remote marine areas are not safe from being contaminated by microplastics carried across large distances from their suspected source. 

On top of this, the findings now raise real concern over the growing pressures being faced by populations of reef manta rays – a species that eats plankton by a process known as filter feeding – now at growing risk of ingesting microplastics and suffering the, as yet, not-fully-determined physical consequences.

As filter feeders, long-term exposure to plastic ingestion not only increases exposure of manta rays to harmful chemicals associated with things such as reduced fertility and immune responses, but it also puts the species at the real risk of clogging their filtering systems.

“We mainly found black and blue fibres, and over half of the particle were found to be synthetic, including polyester, polypropylene, and nylon which are all microfibres that tend to originate from clothing,” said Dr Jessica Savage, the lead author on the study and researcher with Zoological Society London.

“While protected areas are created to protect an endangered species like the reef manta rays from things like fishing and other anthropogenic impacts, plastic – due to it drifting across country boundaries and certainly across the boundaries of protected areas, is a pervasive and systemic issue that needs global action to address.”

A previous study has shown that 99.9% of the macro-plastics in the Chagos Islands – those such as plastic water bottles – come from outside of the archipelago. An area that consists of just one human-inhabited island, the Chagos archipelago is sparsely populated. Perhaps most shocking among the findings of this recent study is that higher concentrations of microplastics were found around the archipelago’s uninhabited atolls.

“It all suggests that these micro-fibres are being carried to the region from elsewhere,” said Dr Savage. “As well as that, the fact that what we found were mainly black and blue fibres, it reinforced the idea that these are being emitted by the rivers around the Indian Ocean.”

Egmont Atoll on the Chagos archipelago has been designated an Important Shark and Ray Area on the IUCN, making it an important aggregation and feeding area for reef manta rays.

The long-term impacts of microplastic ingestion on reef manta rays is hard to monitor. However, given that this is an endangered species with a long life history – meaning they have a slower reproductive rate – the chronic long-term impact could include pressure on their fertility and population growth. It means their conservation can be critically impeded.

“We also forget that in the process of making plastic, they include lots of plasticisers and toxic chemicals that add to the problem for marine life. Every bit of these fibres is carrying a toxic burden that accumulates in the manta ray. And where there are studies, they show quite concerning impacts, not just on marine life but wildlife everywhere as well as humans,” said Dr Heather Koldewey, the supervising researcher on the study.

Plastic pollution is a systemic issue that is rooted not only in infrastructure and manufacturing but in societal connection to overconsumption and the environment.

One of the key tools – currently in development – to address this issue is the Global Plastics Treaty, which, alongside standardising the kinds of chemicals used in plastic production and setting recycling rates and the potential upper limit for the production of virgin plastics, will work alongside regulatory frameworks including Extended Producer Responsibility and Right to Repair to help transition the current linear – take, make, throwaway – economy into something more circular.

“In the context of remote islands, the Global Plastics Treaty is really, really important because there are so few solutions we can implement in-situ,” said Dr Savage. “Beach cleans, washing machine filters – these are downstream solutions, but stemming this at the start would reduce the chemicals used, or the polymers used, or making it legally-binding that any products you make have a reuse strategy.

“I really believe that The Global Plastics Treaty is a ‘once in a planet opportunity.’”

Dr Jessica Savage’s paper – No escape from microplastics: Contamination of reef manta ray feeding areas in a remote, protected archipelago – is now published in the journal The Society for Conservation.

Click here for more from the Oceanographic Newsroom.