A new study has found that about 14 million tonnes of microplastic reside on the ocean floor. This conservative estimate was reached by the Commonwealth Scientific and Industrial Research Organization, or C.S.I.R.O., Australia’s national science agency. This estimate ranges from 9.25 million to 15.87 million tons of microplastics or 8.4 to 14.4 million tonnes. Microplastics are fragments of plastic measuring between five millimetres and one micrometre and have received less attention than single-use plastic products even though they can be equally toxic.

The estimates are far more than those for plastic on the ocean’s surface and equivalent to 18–24 shopping bags full of small plastic fragments for every foot of coastline on every continent except for Antarctica. Millions of tons of plastic enter the world’s water bodies with numbers ranging from 4.4 million to 8.8 million tons annually.

Microplastics find their way to the ocean floors and due to their size, are often ingested by plankton and fish which can then end up in the human food chain. The study aimed to find out the extent of microplastic pollution in deeper areas of the oceans since ‘this knowledge is imperative for predicting the distribution and potential impacts of global plastic pollution.’ 

The researchers quantified microplastics in deep-sea sediments from the Great Australian Bight using an adapted density separation and dye fluorescence technique, analysing sediment cores from six locations, ranging from 288 to 356 km from the Australian coastline. They found substantially higher microplastic counts than recorded in other similar analyses of deep-sea sediments, with the number of such fragments increasing as surface plastic counts increased, and as the seafloor slope angle increased. 

The presence of microplastics in deep-sea locations underscore the fact that plastic pollution in the marine environment is a bigger problem than previously estimated. As quoted in this article, Britta Denise Hardesty, a principal scientist for C.S.I.R.O. and an author of the study, said, ‘It really points to the ubiquity of the problem. It is really everywhere all the time and increasing.’