Ocean microplastics carry ‘memory’ of their movement, study finds

Microplastics which float through the oceans have a “memory” of their previous movements which influences the way they travel, research has found.

A study from Heriot-Watt University found that rather than responding only to the waves around them at any given moment, the earlier motion of larger microplastic particles influences where they travel.

It is hoped the study will pave the way for more accurate predictions of where marine plastic pollution could end up.

Microplastic particles measure less than five millimetres in length, often coming from larger plastic pieces which have broken apart.

They can be harmful to ocean life and ecosystems.

Current understanding of microplastic particles often assumes that their movement in the ocean only depends on their immediate surroundings.

However the study, published in the journal Physics of Fluids, determined that for many larger microplastic particles previous interactions with ocean waves continued to shape their movement over time.

The researchers identified the point at which these “memory effects” become significant.

Dr Cathal Cummins is an associate professor in the School of Mathematical and Computer Sciences at Heriot-Watt University.

He said: “Plastic pollution is one of the defining environmental challenges of our time, but we still do not fully understand how microplastics move through the ocean or where they ultimately end up.

“Our work shows that larger microplastic particles effectively carry a memory of their previous motion through the water.

“That memory changes how they respond to waves and can have a significant impact on how far they travel.

“By accounting for these memory effects, we can develop more reliable mathematical models that help scientists better predict the movement of marine plastic pollution.

“Better predictions will ultimately support environmental monitoring, risk assessment and future strategies to protect marine ecosystems.”

Mary Eby, PhD researcher at Heriot-Watt University, said: “This should help future studies build a more complete picture of how microplastics are transported through the ocean and provide additional context for past studies in the existing literature.”