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Microplastics are 'to blame' for the decline of fish populations, study suggests

Posted on 03/06/16 in News

Microplastics are 'to blame' for the decline of fish populations, study suggests

NOTE: The scientific paper that this article was based on was retracted by the journal Science in May 2017 after an inquiry concluded the authors of the study were "guilty of scientific dishonesty". 

By Lewis Smith

Plastic is killing fish, stunting their growth and hamstringing their ability to avoid predators, a study shows.

Scientists warned that the impact of microplastics, tiny fragments less than 5mm long, could be having a “profound” affect on fish populations.

An estimated 300 million tonnes of plastic is manufactured every year and huge quantities end up in the seas and waterways. One study last year estimated there are 5.25 trillion pieces of plastic in the seas.

Much of the plastic found in water consists of tiny beads created for use in beauty products while other particles come from larger items that have broken down into fragments. However, while it can break down into tiny pieces, plastic can survives in the environment for hundreds or even thousands of years.

Researchers looking at the impact of microplastics on fish analysed the survival of perch at the larval stage and found that exposure to plastics could have a catastrophic affect.

They found that the proportion of eggs that hatched successfully was much lower if there was plastic in the water. Eggs in clean water had a 96 per cent chance of hatching whereas those with high levels of plastic in the water had only an 81 per cent hatch rate. Those in waters containing an average quantity of plastic - compared to coastal areas - had an 89 per cent hatch rate.

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The research team from the Uppsala University in Sweden also discovered that if the larval fish had the opportunity the larval fish would switch from their natural diet of zooplankton to plastic, having severe consequences for their rate of growth.

Survival of the fish exposed to plastic was further affected by changes in their behaviour which meant they ignored chemical signals in the water warning them of the presence of predators.

In tests the scientists found that fish exposed to microplastics in tanks were caught and eaten four times faster than those kept in clean water.

Dr Oona Lönnstedt warned: “If early life-history stages of other species are similarly affected by microplastics, and this translates to increased mortality rates, the effects on aquatic ecosystems could be profound.

“Fish reared in different concentrations of microplastic particles have reduced hatching rates and display abnormal behaviors. The microplastic particle levels tested in the current study are similar to what is found in many coastal habitats in Sweden and elsewhere in the world today.”

The fish used in the study were Eurasian perch, Perca fluviatilis, which have declined in recent years in the Baltic Sea.

Dr Lönnstedt and her colleague Professor Peter Eklöv said their finding suggested plastic pollution could be one of the main reasons for the decline.

Professor Eklöv said: “Increases in microplastic pollution in the Baltic Sea and marked recruitment declines of the coastal keystone species, like perch and pike, have recently been observed. Our study suggests a potential driver for the observed decreased recruitment rate and increased mortality.”

In their study, published in the journal Science, they concluded: “Exposure to environmentally relevant concentrations of microplastic polystyrene particles inhibits hatching, decreases growth rates, and alters feeding preferences and innate behaviors of European perch larvae.

“Our results demonstrate that microplastic particles operate both chemically and physically on larval fish performance and development.”

Picture: a perch larva with ingested microbeads clearly visible. Credits: Oona Lönnstedt

Lönnstedt O.M., Eklöv P. 2016 Environmentally relevant concentrations of microplastic particles influence larval fish ecology. Science (doi: 10.1126/science.aad8828)