Microplastics are found concentrated in seas. By the year 2100, 69% of the water surface of the Mediterranean and 54% of the water surface of the Yellow Sea could even show unfavourable conditions for marine life due to the pollution with microplastics, a new study, conducted by the Flanders Marine Institute (VLIZ) and the universities of Ghent, Gothenburg, Utrecht and Wageningen reveals.
Anno 2010, 0.17% of the global ocean surface layer is impacted by microplastic pollution, posing a threat to the marine ecosystem. Under the worst case scenario, this fraction will increase to 1.62% of the ocean surface layer by 2100, an area as big as ten times the size of France. In particular, the Mediterranean Sea and the Yellow Sea, two enclosed basins facing high human pressure, are under serious threat.
Plastic particles in the upper 5 meter sea water
The new study assessed the risk of floating microplastics (< 5 mm) to marine ecosystems worldwide. The researchers compared ambient concentrations of microplastics in the surface layer of the global ocean (up to five meter deep) with available ecotoxicity data. By doing so, the scientists determined the concentration of microplastics above which adverse ecological effects are likely to occur. Moreover, based on the ever-increasing production of plastics since the 1950s, the researchers predicted the risks of microplastics for the marine ecosystem in 2050 and 2100.
High concentrations in eastern Mediterranean Sea
The study shows substantial spatial differences in the risk of microplastics in the ocean surface layer. The Mediterranean Sea and the Yellow Sea (near China) in particular have the dubious honour of harbouring the highest concentrations of microplastics in the surface layer of the ocean (up to a depth of five meter). The highest microplastic concentrations were estimated to be over 40 microplastics per liter of seawater in the Eastern part of the Mediterranean Sea and over 50 microplastics per liter of seawater in the Yellow Sea.
These values are lower than the predicted median concentration of 121 microplastics per liter of seawater above which adverse ecological effects are likely to occur. However, this unacceptable level varies between a maximum of 1,500 microplastics per liter (best case scenario) and a minimum of eight microplastics per liter (worst case scenario). Hence, this study shows that certain organism in parts of the Mediterranean Sea and the Yellow Sea are currently (anno 2010) already at risk. 16% and 5% of the surface areas of the Mediterranean Sea and the Yellow Sea respectively were exposed to microplastic concentrations exceeding the most strict unacceptable level of eight microplastics per liter of seawater.
Sea could exhibit unfavourable conditions for marine life
If the plastic production continues to increase at the current rate, scientists expect the global plastic production to quadruple to 1,800 megatons by 2100. With the increasing plastic production, the chance that the unacceptable concentration of microplastics will be exceeded increases. The researchers predict that under a worst case scenario, 69% of the surface area of the Mediterranean Sea and 54% of surface area of the Yellow Sea will exhibit unfavourable conditions for marine life due to microplastic pollution by 2100.
Higher chance of altered ecosystems
This study shows that the risk at the global ocean surface related to the pollution by microplastics is going in the wrong direction. The increasing microplastic concentrations, which already exceed the safe standards locally, will lead to a higher chance of altered ecosystems. Additional studies investigating the interaction between microplastic exposure and other global change stressors in marine ecosystems are urgently needed. In this way, policymakers can determine priorities and implement targeted measures to tackle realistic environmental risks.