Horizontal distribution of surface microplastic concentrations and water-column microplastic inventories in the Chukchi Sea, western Arctic Ocean

The recent influx of microplastics into the Arctic Ocean may increase environmental stress on the western Arctic marine ecosystem, which is experiencing significant sea-ice loss due to global warming. Quantitative data on microplastics in the western Arctic Ocean are very limited, and the microplastic budget of the water column is completely unknown. To fill in gaps in our knowledge of Arctic microplastics, we observed surface concentrations (number of particles per unit volume of seawater) of meso- and microplastics using a neuston net, and we observed wind speeds and significant wave heights in the Chukchi Sea, Bering Strait, and Bering Sea. From these observations, we estimated the total number (particle inventory) and mass (mass inventory) of microplastics in the entire water column by taking into account the effect of vertical mixing. The particle inventory of microplastics in the Chukchi Sea ranged from 0 to 18,815 pieces km-2with a mean and standard deviation of 5236 & PLUSMN; 6127 pieces km-2. The mass inventory ranged from 0 to 445 g km-2 with a mean and standard deviation of 124 & PLUSMN; 145 g km-2. Mean particle inventories for the Chukchi Sea were one-thirtieth of those for the Arctic Ocean on the Atlantic side and less than onetenth of the average for the global ocean, suggesting that the Chukchi Sea is less polluted. However, the annual flux of microplastics from the Pacific Ocean into the Chukchi Sea, estimated from microplastic concentrations in the Bering Strait, was about 5.5 times greater than the total amount of microplastic in the entire Chukchi Sea water. This suggests that microplastic inflows from the Pacific Ocean are accumulating in large amounts in reservoirs other than the Chukchi Sea water (e.g., sea ice and seafloor sediments) or in the downstream regions of the Pacific-origin water.

Automated summary

The recent influx of microplastics into the Arctic Ocean is causing increased stress on the western Arctic marine ecosystem which is already dealing with sea-ice loss due to global warming. However, there is limited quantitative data on microplastics in the western Arctic Ocean, and the microplastic budget of the water column is unknown. To address this knowledge gap, the researchers observed surface concentrations of microplastics using a neuston net and estimated the total number and mass of microplastics in the entire water column, considering the effect of vertical mixing. The results showed that the Chukchi Sea has lower pollution levels compared to other regions, but there is a significant influx of microplastics from the Pacific Ocean accumulating in various reservoirs.