Microplastics affect individual fish differently, study finds

It appears all fish might not be equal when it comes to how they are affected by microplastics, according to new research from the University of Essex.

A new study shows that within the same species of fish there are differences in how much microplastic they individually ingest. It also found the fish that ingested the largest amount of microplastic may be more vulnerable to predators as their startle response was slower.

The rising tide of plastic debris in the world’s oceans has become one of the main ecological issues of our time. Microplastics, which are particles of less than 5mm diameter, are especially problematic as they are widespread in our oceans and their small size make them available for ingestion by a wide range of marine organisms.

Animals in their early stages of development, such as tiny fish larvae, are particularly vulnerable and may mistake microplastic particles for food.

Essex researchers, working with colleagues from the Interuniversity Institute for Marine Sciences in Israel, carried out a range of controlled experiments where they repeatedly exposed early-stage sea bream to equal concentrations of microplastics.

The study, led by Dr Gerrit Nanninga, from the University’s School of Life Sciences, found some of the fish consistently consumed large numbers of microplastics, while others consistently avoided them.

“More importantly, we also found that fish which had ingested large quantities of microplastics exhibited a reduced startle response – which means they could be at greater risk of predators,” explained Dr Nanninga. “Such variation could have a strong impact on the way that microplastic pollution affects populations – some individuals may be more/less affected, simply because they have an innate tendency to consume/avoid these potentially harmful particles.”

Dr Nanninga said the level of microplastic ingestion could be related to certain personality traits of individual fish – with more active individuals ingesting more particles than less active fish.

The study, published in the Journal of Hazardous Materials, suggests that the impact of microplastic pollution may not be the same across populations. Instead some individuals may consistently be more affected than others due to differences in feeding behaviour. With plastics increasingly replacing real food items this could mean individuals that should  naturally have a selective advantage due to their feeding efficiency may now be the ones most impacted by microplastic contamination.

Dr Nanninga added: “Ignoring inter-individual variation in microplastic ingestion during experiments may lead to inaccurate conclusions about the consequences of microplastic exposure on fish.”