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.” 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.