Key species for cleaning up marine environment is disrupted by microplastics

The extent to which microplastics are impairing the lifecycle of the hermit crab, a key species in marine environments, has been outlined by scientists at Queen’s University Belfast (QUB).

These crabs are responsible for “cleaning up” the sea through eating up decomposed sea-life and bacteria and also act as an important host for other marine species.

The QUB research conducted with Liverpool John Moores University is another indication of how "the microplastic pollution crisis is threatening biodiversity", according to Dr Gareth Arnott from QUB School of Biological Sciences.

Currently up to 10 per cent of global plastic production ends up in the sea though the understanding of how this affects marine life is limited. Their research, he said, reveals the impact of plastics on hermit crabs, “which play an important role in balancing marine ecosystems”.

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Hermit crabs do not develop their own shells but instead take shells from snails to protect their soft abdomens. As a hermit crab grows over the years, it will need to find a succession of larger and larger shells to replace the ones that have become too small. These shells are vital in protecting and enabling hermit crabs to grow, reproduce and survive.

The researchers in a study published on Wednesday in Biology Letters, found that when hermit crabs were exposed to microplastics, “they were less likely to later touch or enter high-quality shells.”

“Our research shows that exposure to microplastics can have important effects on animal behaviour. More specifically, in this case it had a detrimental effect on shell selection behaviour in hermit crabs. As this behaviour is vital for hermit crab survival and reproduction, there could be important long-term consequences,” said Dr Arnott, who is lead author of the study.

To investigate the impact of microplastic exposure, the research team divided hermit crabs between experimental tanks, half containing microplastics while the other half had no plastic. After five days, the hermit crabs were moved into low-quality shells with the option for alternative high-quality shells offering more protection.

Dr Arnott added: “Our research shows for the first time how microplastics are disrupting and causing behavioural changes among the hermit crab population.”

By providing a hard, mobile surface, hermit crabs are also “walking wildlife gardens” he said. They host more than 100 invertebrate species – far more than live snails or non-living substrates.

Additionally, commercially valuable species such as cod, ling, and wolf fish prey on hermit crabs. “With these findings of effects on animal behaviour, the microplastic pollution crisis is therefore threatening biodiversity more than is currently recognised so it is vital that we act now to tackle this issue before it becomes too late.”