Marine amphipods increase micro-plastic pollution

Ocean pollution by micro-plastics is an acknowledged and growing threat to marine ecosystems. Now, in a biting irony, it seems that at least one member of those ecosystems is making its own hefty contribution to the problem.

Research by scientists at the School of Biological and Marine Sciences at the University of Plymouth in the UK has found that amphipods of the species Orchestia gammarellus are capable of transforming a discarded carrier bag from a single large oceanic hazard into 1.75 million microscopic ones.

The common amphipod, which looks like a tiny shrimp, is a detritivore – a species that consumes dead organic material. It also, however, feeds off plastic, particularly that which has accumulated a layer of organic material across it, known as a biofilm, during its time floating in the water.

The team, led by Daniella Hodgson, initially set out to determine whether the presence of a biofilm layer affected the rate at which O. gammarellus consumed different types of plastic.

In a paper published in the journal Marine Pollution Bulletin, the team reports that experiments in the laboratory as well as shoreline observations found that concentrations of amphipods stretched and tore plastic debris, creating high levels of micro-plastics found in and nearby their faeces.

The animals were equally adept at destroying conventional, degradable and biodegradable plastics, but the presence of biofilm increased the rate of destruction by about four times.

“An estimated 120 million tonnes of single use plastic items – such as carrier bags – are produced each year and they are one of the main sources of plastic pollution,” says co-author Richard Thompson.

“They already represent a potential hazard to marine life, but this research shows species might also be contributing to the spread of such debris. It further demonstrates that marine litter is not only an aesthetic problem but has the potential to cause more serious and persistent environmental damage.”

In related news, another paper looking at the consumption of micro-plastics by marine organisms has been condemned by Swedish authorities following its removal from the journal Science, the result of ethical concerns and claims that the results may have been fabricated.

The academic site RetractionWatch reports that the paper, Environmentally relevant concentrations of micro-plastic particles influence larval fish ecology, by Oona Lonnstedt and Peter Eklov or Uppsala University in Sweden, was pulled by the journal in early April, and an investigation launched by the university.

In part, the researchers looked at the behaviour of European perch larvae after exposure to micro-plastics and found that their ability to detect and respond to predators was significantly diminished.

The decision to retract was made after it was revealed that ethics approvals for exposing the young fish to predators was granted only after the research had already been conducted.

The paper had already been the subject of heated debate. RetractionWatch reports that one of the scientists’ principal conclusions – that fish larvae preferred to eat plastics instead of their natural food – was strongly contested by other researchers.

An investigation in April 2017 by Sweden’s Central Ethical Review Board found that there were critical flaws in the research, accused the researchers of “scientific dishonesty”, and called for a retraction.

Uppsala University’s investigation wrapped up early in December. It found several violations by the scientists, including the key discovery that the research could not possibly have been conducted within the timeline described in the paper.

Disciplinary action is pending.