In the last years, concern about anthropogenic contamination has clearly increased due to its environmental effects. In particular, marine litter is one of the most worrying marine pollution problems for which plastics account for 80-90 %, since their low density and light weight make them easy to spread. Once in the ocean, they can break down into smaller particles through physical and chemical processes which increases their bioavailability. Those fragmented particles within the 1 μm-5 mm size range (their largest dimension) are widely named as microplastics, though it should additionally be mentioned that they are also being produced with that size for certain applications. In the particular case of plastic particles bellow 0.5-1 mm, it should be indicated that although they cannot be easily seen with the naked eye, they are widely spread in the environment being quite difficult to separate, detect and quantify them. For all these reasons, their study in any ecosystems and, in particular, in living organisms constitutes a great challenge.

In Spanish universities, each undergraduate student and master’s degree student, must develop a Final Degree Project (FDP) or a Final Master’s Degree Project (FMDP), respectively, which consists of an autonomous work carried out in the last semester of the last year of the degree. Both types of projects should be carefully written and presented in a public defense, according to the specific guidelines of the subject. In such project, the student must demonstrate the knowledge acquired and the skills developed, either through a bibliographic research or an experimental work.

As an FDP or FMDP dealing with marine pollution, we propose a fascinating and easy experimental work with a multidisciplinary approach suitable for the degrees of Biology, Environmental Sciences or Marine Sciences, or master’s degrees like Marine Biology, among others. In this work, students must analyse and quantify the content of microplastics within the digestive tracts and the gonads of sea urchins. They will be able to expand their skills in sampling, sample treatment, statistical analysis, etc., and also their knowledge about the importance of the monitoring of microplastics in the marine food chain and how contamination by microplastics affects marine organisms. The obtained results can be considered as an indicator of the environmental status of the sampling zone, but they can also increase the environmental awareness of any student.