NanoMare expedition: nanoplastics in the North Atlantic

Written by Helge Niemann, Chief Scientist during cruise AW-109 

I escaped the heatwaves in the Netherlands, apparently the new normal, even if some people do not like to admit it. But that is another story… We went out into the North Atlantic for another reason: plastics.

We have all heard about it: plastic waste floating in our oceans and its negative consequences for marine life. A never-receding avalanche of waste pours out of our civilisation into the sea. Larger plastic objects float at the sea surface, drift with the currents and are broken into ever-smaller fragments by the sun’s scorching UV light and the smashing force of the waves. In this way, larger pieces become smaller; macroplastics become microplastics, until…

…well, until what?

We already discovered that at least some of these larger macro- and microplastics are broken down into particles smaller than one-thousandth of a millimeter. That is very small. Imagine a thin human hair: it is at least 50 times thicker than one-thousandth of a millimeter. These tiny plastic particles - smaller than one-thousandth of a millimeter -are called nanoplastics and are invisible to the naked eye.

Nanoplastics also behave rather oddly. Larger plastic objects usually floats or sinks. For example, plastic bags are often made of polyethylene (PE) and float, while soda bottles are made of polyethylene terephthalate (PET) and – if not closed with a lid - sink. But nanoplastics neither float nor sink, regardless of whether they consist of PE, PET or another type of plastic. Nanoplastics behave like milk in coffee: the milk’s tiny fat droplets remain evenly dispersed, neither immediately rising to the surface as cream nor sinking to the bottom of the cup.

For the ocean, this means that nanoplastics can be distributed throughout the water column, from the sea surface to the deep sea. Almost all marine life may therefore come into contact with nanoplastics. We found that nanoplastics constitute the lion’s share of plastic pollution in the North Atlantic (ref. ten Hietbrink et al., Nature 2025). However, we do not yet know exactly how much nanoplastic is out there globally or how it affects marine life.

Are nanoplastics concentrated near the ocean surface, where they form from macro- and microplastics? Do nanoplastic concentrations differ when comparing for example arctic, temperate and subtropical regions? How much has already reached the deep sea? What happens to microbes - the base of the marine food web - when they are exposed to nanoplastics? What is the fate of nanoplastics in the ocean: do they eventually break down completely

These are some of the many questions that we are trying to answer with the data collected during this expedition. Funding from the EU has allowed me to establish the NanoMare project and bring together an excellent team of scientists - and we are fortunate to conduct this expedition aboard the shiny new flagship of the Dutch research fleet, RV Anna Weber-van Bosse.

Over the coming weeks, we will breathe science: collecting samples, making measurements, discussing our findings and starting experiments. And we will cover a wide geographical range, from the ice-cold Arctic waters to the balmy subtropical waters around the Azores - during expedition AW-109.