Proof of fish larvae eating plastics at sea


Plastics in marine environment

Image left - Selection of microplastics from water samples. (A) Blue fibre; (B) Red fibre, polyester; (C) Blue fragments, (D) Black bead. Middle and right, dissected fish larvae that had ingested microplastics (circled). (A) Whiting with 310 mm rayon fibre; (B) Thickback sole with 270 mm rayon fibre; (C) Common dragonet with 2 blue nylon fibres (220 mm and 230 mm). Image credit: M Steer.

PML scientists and colleagues from Plymouth University have verified and pictured examples of fish larvae ingestion of microplastics, including fibres, in the ocean.

This study, now published, is the first of its kind to simultaneously assess waterborne microplastic concentrations and ingestion in fish larvae, whilst also confirming the suspected particles to be plastic polymers.

Microplastics (plastic less than 5 mm in size) have now been documented in marine environments worldwide, where they pose a potential risk to all marine life. Just how small juvenile organisms such as fish larvae, which are of ecological and economical benefit, interact with and are affected by microplastics is however still poorly understood.

The researchers in this study assessed the occurrence of microplastic ingestion in wild fish larvae off the coast of Plymouth. They found that between April and June 2016, 2.9 % of fish larvae sampled had ingested microplastics, of which 66% were blue fibres closely resembling those found in water samples taken at the same time.

In coastal shelf seas, such as those surrounding the UK, the environment is highly productive, supporting large fisheries,  however it also experiences high levels of microplastic pollution. In these coastal habitats, fish have an important ecological and economic role but in their early life stages, planktonic fish larvae are vulnerable to pollution, environmental stress and predation.

The study demonstrated that Whiting (Merlangus merlangus) was the predominant species with ingested microplastics (reflecting their abundance in the populations sampled). Microplastic concentrations decreased with distance from the coast of Plymouth, whilst fish larval concentrations increased. Incidences of ingestion were found to decrease with distance from the coastline, which illustrates the effect of decreasing waterborne microplastic concentrations.

Madie Steer, who completed this work at PML as part of her MRes with Plymouth University commented:

“The aim of this study was to assess not only if fish larvae were ingesting microplastics, but also if there was a spatial pattern of ingestion. We know that microplastics are ingested by many different organisms, but we now need to understand why some studies report such high ingestion rates in the wild and others, like this one, are relatively low. Is it the organisms’ physiology or behaviour, or is it the characteristics of the waterborne microplastics?”

PML Senior Scientist and co-author on the study Dr Pennie Lindeque also commented:

“While the incidence of ingestion was relatively low in this study, the fish larvae have only been in the water column feeding for a matter of days to weeks. Considering that at our sampling station closest to shore there
were 27 times more plastic than fish larvae per cubic meter of water, and that plastics take centuries to degrade, then the problem is only set to get worse.”

Marine plastic debris is a result of poor waste management and accidental losses from fishing, industry, shipping and tourism among other sources. The rise in popularity of synthetic fibres such as nylon and polyester has meant that microscopic fibres are released into coastal waters through sewage outfall. There is currently no means of removing these microplastic fibres from waste water.

Madie Steer concluded:

“When there are high numbers of plastics in the water alongside large populations of animals that we know will ingest them then we expect there to be a higher level of ingestion. For commercially important fish species in particular it is vital that we understand if microplastics will affect their survival, so more research is needed on a much larger scale”.

This study provides important baseline ecological data for further research in the future, by illustrating the correlation between microplastics in coastal regions and the incidence of ingestion in fish larvae.

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