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Queen’s University Belfast Research Shows How Plastics Threaten Biodiversity of Marine Life

13th October 2021
The research found that microplastics are affecting the behaviour of hermit crabs
The research found that microplastics are affecting the behaviour of hermit crabs

New research at Queen’s University highlights the impact that microplastics are having on hermit crabs, which play an important role in balancing the marine ecosystem.

The research found that microplastics are affecting the behaviour of hermit crabs, namely their ability during shell fight contests, which are vital to their survival.

There is a strong association between hermit crabs and their shelters or shells, which are taken from marine snails to protect their soft abdomens. As the 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. They can achieve this through a contest, termed a shell fight, involving the ‘attacker’ rapping their shell against the ‘defender’ in an attempt to evict the opponent from its shell. In these contests, the hermit crabs will fight a competitor to secure the shell that they favour. These shells are vital in protecting and enabling hermit crabs to grow, reproduce and survive.

The new study builds on previous research by Queen’s University that showed hermit crabs were less likely to touch or enter high-quality shells when exposed to microplastics.

Hermit crabs were less likely to touch or enter high-quality shells when exposed to microplasticsHermit crabs were less likely to touch or enter high-quality shells when exposed to microplastics

The new study, published in Royal Society Open Science, provides a more in-depth insight into how the hermit crabs behaviour is affected when exposed to microplastics. The microplastics impair both the attacking and defending behaviour of hermit crabs during contests, impeding their ability to secure the larger shell that is required for both their growth and survival.

The research involved keeping hermit crabs in two tanks: one which contained polyethylene spheres (a common microplastic pollutant) and one without plastic (control) for five days. The team simulated the environment to encourage a hermit crab contest through placing pairs of hermit crabs in an arena, giving the larger crab a shell that was too small and the smaller crab a shell that was too big. Plastic-exposed hermit crabs displayed weaker attacking behaviour (known as rapping) during fights than crabs that were not exposed to plastic. Microplastics also reduced the ability of defending crabs to properly assess their attackers during contests and impaired their decision to give up their shell earlier.

Hermit crabs are known as scavengers as they recycle energy back into the ecosystem through eating up decomposed sea-life and bacteria. As such they play a vital role in rebalancing the ecosystem and are an important part of marine life.

Manus Cunningham from Queen’s University and one of the lead researchers on the paper, said: “These findings are hugely significant as they illustrate how both the information-gathering and shell evaluations were impaired when exposed to microplastics.

“Although 10% of global plastic production ends up in the ocean, there is very limited research on how this can disrupt animal behaviour and cognition. This study shows how the microplastic pollution crisis is threatening biodiversity more than is currently recognised.”

Dr Gareth Arnott, the principal investigator of the project said: “This study provides an insight into the potential for microplastics to alter important aspects of animal behaviour that are critical for survival and reproduction. We need to further investigate how microplastics affect their behaviour and the consequences, armed with this knowledge to advocate for change to protect our ecosystem.”

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Marine Science Perhaps it is the work of the Irish research vessel RV Celtic Explorer out in the Atlantic Ocean that best highlights the essential nature of marine research, development and sustainable management, through which Ireland is developing a strong and well-deserved reputation as an emerging centre of excellence. From Wavebob Ocean energy technology to aquaculture to weather buoys and oil exploration these pages document the work of Irish marine science and how Irish scientists have secured prominent roles in many European and international marine science bodies.

 

At A Glance – Ocean Facts

  • 71% of the earth’s surface is covered by the ocean
  • The ocean is responsible for the water cycle, which affects our weather
  • The ocean absorbs 30% of the carbon dioxide added to the atmosphere by human activity
  • The real map of Ireland has a seabed territory ten times the size of its land area
  • The ocean is the support system of our planet.
  • Over half of the oxygen we breathe was produced in the ocean
  • The global market for seaweed is valued at approximately €5.4 billion
  • · Coral reefs are among the oldest ecosystems in the world — at 230 million years
  • 1.9 million people live within 5km of the coast in Ireland
  • Ocean waters hold nearly 20 million tons of gold. If we could mine all of the gold from the ocean, we would have enough to give every person on earth 9lbs of the precious metal!
  • Aquaculture is the fastest growing food sector in the world – Ireland is ranked 7th largest aquaculture producer in the EU
  • The Atlantic Ocean is the second largest ocean in the world, covering 20% of the earth’s surface. Out of all the oceans, the Atlantic Ocean is the saltiest
  • The Pacific Ocean is the largest ocean in the world. It’s bigger than all the continents put together
  • Ireland is surrounded by some of the most productive fishing grounds in Europe, with Irish commercial fish landings worth around €200 million annually
  • 97% of the earth’s water is in the ocean
  • The ocean provides the greatest amount of the world’s protein consumed by humans
  • Plastic affects 700 species in the oceans from plankton to whales.
  • Only 10% of the oceans have been explored.
  • 8 million tonnes of plastic enter the ocean each year, equal to dumping a garbage truck of plastic into the ocean every minute.
  • 12 humans have walked on the moon but only 3 humans have been to the deepest part of the ocean.

(Ref: Marine Institute)

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