Modelling marine microplastics’ movements

Researchers led by Newcastle University’s Dr Hannah Kreczak have identified the processes that underpin the trajectories of microplastics below the ocean surface, and have developed a mathematical model that may support the effort to remove plastic waste from the oceans.

Publishing their findings in the journal Limnology and Oceanography, the study presented a simple analytic model that described the deterministic dynamics of long-time vertical motion of buoyant microplastics, and the model the team developed used equations governing vertical particle position and algal population dynamics.

The team found that the smallest particles are extremely sensitive to algal cell attachment and growth, suggesting that a higher concentration of biofouled microplastic is expected to be found subsurface, rather than at the ocean's surface. This indicates these particles are always submerged at depths surrounding the base of the euphotic zone, where there is just light to support photosynthesis.

This is significant, because it is currently not known what happens to the vast majority of plastic particles once they enter the ocean, and 99% of microplastics are considered ‘missing’.

This new model, therefore, has the potential to understand the distribution of fouled plastics in the ocean and therefore the ecological impact, particularly in areas of high concentration.

Dr Kreczak said: “Mathematical modelling has been extremely beneficial in identifying hot-spots for marine plastic pollution on the ocean surface. I hope this research can be a constructive step in understanding the impact plastic pollution has below the surface and aid in the effort towards a more sustainable ocean.“

Dr Andrew Baggaley, one of the report’s co-authors, said, “This is an exciting first step in our project to develop a comprehensive modelling framework to understand the transport of microplastic particles and their distribution in the oceans.”

To read Newcastle University’s news announcement, visit their news page.

To read the study’s abstract, visit the Journal of Limnology and Oceanography’s webpage.