Around four billion minute fibres could be littering each square kilometre of some of the world’s deep seas, demonstrating that plastic debris is now creating cause for concern in some of the remotest parts of the marine environment.
That is one of the findings of a pioneering international study examining the scale of the presence of microplastics at depths of up to 3500m in parts of the Indian and Atlantic Oceans, and the Mediterranean Sea.
Existing research had shown that in recent decades plastic debris has become almost omnipresent on the world’s coastlines, but the extent of its concentration close to shorelines had not increased in line with predictions based on the production and use of plastic.
However, the current study – led by scientists from Plymouth University and the Natural History Museum – indicates this may be because microplastics have sunk to the ocean floor, with the number of fibres recorded as being up to four times more abundant in the deep seas than in shallow and coastal waters.
In fact, the current study has led scientists to suggest – in areas of the Indian Ocean at least – that around 4 billion fibres per km² would be present in seamounts.
Richard Thompson, Professor of Marine Biology at Plymouth University, who co-ordinated work to identify plastics in the deep sea sediments, said:
“Marine debris, mostly consisting of plastic, is a global problem, negatively impacting wildlife, tourism and shipping. However, despite the durability of plastic, and the exponential increase in its production, there has always appeared to be a considerable proportion of the plastic debris that was unaccounted for.”
The study, published in the Royal Society Open Science journal, also involved the University of Barcelona, the University of Oxford and the Scottish Association for Marine Science.
Dr Lucy Woodall, zoologist at the Natural History Museum collected many of the samples and noticed small pieces she thought could be plastics. Dr Woodall said:
“The puzzle for marine scientists has been to establish where plastic debris is going. Part of the answer is that much of this waste is breaking down into fibres invisible to the naked eye and sinking to the sea floor. It is alarming to find such high levels of contamination, especially when the full effect of these plastics on the delicate balance of deep sea ecosystems is unknown.”