An international team of scientists has analysed more than 100 water samples from the Arctic seas. They have found out how microplastics distribution changes in different water bodies. Anfisa Berezina is a doctoral student at St Petersburg University. To clarify the obtained dependences, she performed a detailed statistical data analysis on microplastics distribution, and the morphology, size and chemical composition of particles.

The research findings are published in Communications Earth & Environment.

According to the United Nations Environment Programme (2014), plastic is increasingly found in the world’s marine ecosystems. A potential threat to the marine fauna is presented by small plastic particles up to five millimetres in size and smaller – microplastics. They can disrupt the vital activity of zooplankton, be transmitted along the food chain, and also accumulate hazardous substances on their surface. The Arctic region, which has been considered a place free from plastic pollution for a long time, remains understudied.

The international team of scientists studied how microplastics distribution in the Eurasian Arctic is affected by Atlantic waters and Siberian rivers. The team, headed by Evgeniy Yakushev, Senior Scientist at the Norwegian Institute of Water Research, also included experts from: St Petersburg University; Shirshov Institute of Oceanology of the Russian Academy of Sciences; the University of Edinburgh (Scotland); the Lomonosov Moscow State University Marine Research Centre; and Tomsk Polytechnic University.   

‘The Ob, the Yenisei and the Lena annually bring more than 1,500 square kilometres of continental waters into the Arctic Ocean, forming vast desalinated areas on the Arctic shelf,’ said Eevgeniy Yakushev.

Scientists have not had reliable knowledge yet about the effect of river-borne plastic pollution on marine ecosystems. Our team was the first to assess the dependence of the microplastics distribution on the properties of water bodies of various origins.

Evgeniy Yakushev, Senior Scientist at the Norwegian Institute of Water Research

In the autumn of 2019, during an expedition aboard the research vessel Akademik Mstislav

Keldysh, the scientists took more than 100 samples in four seas of the Arctic Ocean:  the Barents, Kara, Laptev, and East-Siberian Seas.  A total of 60 subsurface water samples from a horizon of three metres and 48 surface neuston samples were collected. The geographic boundaries of these seas do not coincide with the boundaries of water masses, the circulation and interaction of which are the main factors in the transfer of microplastic particles. After analysing the spatial distribution of plastic in the seas under study, the researchers identified two different sources of contamination: the North Atlantic and the Great Siberian Rivers.

The marine-borne microplastics and the river-borne microplastics have distinct physical (size, morphology and weight) and chemical (polymer type) characteristics.  Thus, floating microplastics advected from the North Atlantic are composed mainly of polyethylene, while river-borne floating microplastics are composed mainly of polyester fibres. The distribution of the microplastics types under study is also affected by various factors. The transport of marine plastic is strongly influenced by seasonality in the Arctic (ice-cover formation). River-borne particles enter the Arctic from the vast catchments of Siberian rivers, with their distribution being influenced by the dynamics and volume of carried out fresh water. The researchers believe that, in the future, the properties of the microplastics can be used for identification of the water masses.

This research shows that even the most remote areas of the World Ocean are prone to microplastic contamination. Unfortunately, relatively few samples were collected in the Barents Sea as part of this work. It is where the sixth ‘debris patch’, along with the known debris accumulations in the centres of tropical gyres, is supposed to form.

Anfisa Berezina, a doctoral student at St Petersburg University

‘In the future, it is planned to study in more detail the microplastics distribution in the central part of the Barents Sea and the desalinated areas of the Kara Sea. In addition, the data from the Atlantic Ocean and coastal waters of Antarctica will be analysed. The key priority now is to study the influence of biogeochemical processes on the transport of microplastics in the ocean,’ said Anfisa Berezina.

The research is supported by the grant from the Russian Foundation for Basic Research (project No 20-35-90056).