Summer 2021, Leiden - Delft, The Netherlands

Vliet Clean SUP – Science Unites People

Annelore van der Lint


Water is everywhere. We need to keep it clean and usable. Check out the video impression to see how we did this during the Sub-Vliet Clean Up last Summer.

Citizen science

Research on microplastics in the Vliet


Watch the video impression of the Vliet Clean Up

An integral part of every expedition of The Ocean Movement is doing research on microplastics. Through this research, we show the expedition members that small plastic fragments can be found in almost all seemingly clean water. This shows that the problem is much bigger than just the larger bottles and bags that we can see floating around. We have been examining the North-West European waters since 2016 and took more than 100 samples. We keep searching for ways to expand our research and gain more knowledge on plastic pollution.

With this project we tested a new method to collect and analyze microplastics. Microplastic research are currently analyzed by professionals in the lab. This method is very expensive and therefore not suitable for large-scale application. During the clean-up we tested a cheaper method which can be used by everyone on a large scale. Together we can collect more data.

Microplastics: A total of 10 trajectories were measured with two trawls during the clean-up. The numbers found were converted to number of particles/kilometer for each trajectory. Based on the microplastics found, it was calculated that there are an average of 83,417 pieces of microplastics per km in the Vliet!

The majority of the plastic particles (67%) we found were microplastic measuring a size smaller than 1 mm. The rest (33%) were larger than 1 mm and therefore macroplastic. Most microplastics were found in and just outside Leiden (3 trajectories with 127,745, 203,593 and 337,625 microplastic particles per km). The most abundant plastic particles, with 47.7%, were plastic fragments (plastic particles broken down from larger plastics), 34.6% foil (packaging material) and 11.7% Styrofoam.



Do you want to do it your self? That is possible! We made the protocol available for everyone:

How to make your own Manta (in Dutch) and how to analyse the Sample (in Dutch). For the English version please contact us at [email protected]

Slider Line

The Vliet Clean SUP 2021 - Citizen science pilot

This Project was partly made possible by stichting TAUW Foundation, Nederlandse Waterschapsbank and Hoogheemraadschap van Delfland.


24 - 27 of August 2021.


Leiden to Delft

Event details:

The four day Vliet Clean SUP went from Leiden to Delft.

We cleaned the river Vliet of macroplastic and piloted a new citizen science method to monitor also the smaller fraction of plastics.

2024 The Ocean Movement - Created by Wilde Amsterdam & Webbakery