Microplastics In The Environment: Larval Perch Choose Plastic

By on July 6, 2016
microplastics in the environment

Concern for the problem of microplastics in the world’s waters has only surged within the past decade and researchers are still working to cover all the angles of the issue out there. One clearly important one has to do with how fish will respond to the presence of microplastics in the environment.

As has been proven already, we know that fish and other aquatic organisms mistake microplastics for food. But what are the impacts of this consumption in the long term? Scientists at Sweden’s Uppsala University have completed a series of experiments to find out. Their findings aren’t too promising for the offspring of fish in the future.

Researchers exposed larval perch to to environmentally relevant concentrations of microplastic polystyrene particles, about 90 micrometers in size. The particle levels tested in the study are similar to what is found in many coastal habitats.

After that exposure, the fishes’ behaviors were monitored to see if they acted out of the ordinary or were affected in development. They were found to have reduced hatching rates, showed stunted growth rates and displayed abnormal behaviors.

Stunted growth was related to larval feeding preferences as perch that had access to microplastic particles only ate plastic and ignored their natural food source of free-swimming zooplankton, scientists found. That result marks the first time that an animal has been found to preferentially feed on plastic particles and is a great cause for concern.

Researchers also saw that perch larvae exposed to microplastic particles during development displayed changed behaviors and were much less active than fish reared in water that contained no microplastic particles.

But more importantly, fish exposed to microplastic particles ignored the smell of predators that usually evoke innate antipredator behaviors. To see the impacts of this, researchers placed perch with pike, their natural predator. The perch that had been exposed to microplastic particles were caught and eaten more than four times quicker than control fish. All fish exposed to microplastic particles died within 48 hours.

This response in fish larvae could translate to higher mortality rates as a result of increased predation risk in nature and could cause disruptions in the replenishment and sustainability of fish populations. In the Baltic Sea, for example, increases in microplastic pollution and marked recruitment declines of coastal keystone species like perch and pike have been observed together.

The findings highlight ecologically important and previously underappreciated effects of microplastic particles that enter marine ecosystems. Scientists say they underscore the need for new management strategies or alternative biodegradable products that lower the release of microplastics into the environment, but argue that more research is needed to fully understand the dynamics at play.

Full results of the work are published in the journal Science.

Top image: Larval perch from the Baltic Sea that has filled its stomach with microplastic waste particles. (Credit: Oona Lönnstedt / Uppsala University)

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