Le site de vulgarisation scientifique de l’Université de Liège. ULg, Université de Liège

Microplastics in fish stomachs
12/4/15

An ingenious procedure

The procedure used is simple but somebody needed to come up with it: The stomach contents are treated with “A mixture of bleach and strong acid”. This successful result is the result of a direct collaboration between biologists like France Collard and chemists like Bernard Gilbert and Gauthier Eppe, in the Chemistry Department of ULg. However, the upstream work was particularly arduous because the fish first needed to eat in order to establish what needed to be chemically “digested” and based on this, to identify the substances. “One thing led to another, I found that the best-adapted solution and also the one which worked best was bleach. While beach only takes one night to decompose and degrade substances, other compounds such as potassium hydroxide take three weeks to do so”. The other advantage of bleach is that it is cheap and readily available in retail outlets.

Diagram isolation method


With regard to the results, there were some surprises in store. It should be remembered that one of the first objectives of the thesis was to establish whether fish ingested plastic or not. If the answer to this is yes, then which plastics? Do they correspond to certain criteria of size, shape or colour? And yet, France Collard found mainly cellulose fibres in the stomachs of the fish.  This shows the redundancy of visual observation, which can bias the results. “We demonstrated that many of the particles we thought to be plastic were not. In fact there are more fibres made of cellulose than any other type of pollution caused by human activity”. Cellulose exists naturally so that would have been fine except for the fact that the fibres were coloured. Given that these stains were artificial colorants, there is consequently no possible doubt about the origin of these cellulose fibres (textile fibres, for example). In addition, during the course of her thesis, France Collard observed the same phenomenon in some crustaceans (2). Plastic is therefore supplanted by artificial cellulose fibres. It has been proved that during one washing machine cycle « More than 1, 900 fibres can be released into the water”!

These results, while they differ somewhat from what was expected at the outset, clearly illustrate the effectiveness of this method which combines three valuable advantages: speed, low cost and reliability.

(2) When microplastic is not plastic : ingestion of artificial cellulose fibers by macrofauna living in seagrass macrophytodetritus, Collard France, Remy François, Gilbert Bernard et al., in American Chemical Society, http://hdl.handle.net/2268/185549

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