Microplastics in squishy creature’s poo hurt ocean’s ability to absorb CO2

29 Apr 2019

Photo of a salp. Image: Ken O’Sullivan/Sea Fever Productions

A new study has found that a tiny jellyfish-like creature is eating tonnes of microplastics, thus reducing the oceans’ ability to absorb CO2.

Almost everyone is now aware of the scourge of microplastics and the damage it causes to the world’s oceans, but new findings, including the work of NUI Galway researchers, have revealed yet another worrying discovery.

In a paper published to Environmental Science & Technology, a team including lead author Alina Wieczorek found that microplastics also impact the amount of atmospheric CO2 absorbed by oceans. Along with trees, oceans are a vital resource in efforts to reduce and limit atmospheric CO2 as they act as carbon sinks through biological, chemical and physical processes.

Microplastics are having an effect because they are being eaten in large quantities by salps, a jellyfish-like creature that plays an important part in transporting CO2 to the seafloor. Estimates suggest oceans have captured between one-quarter and one-half of all human-derived CO2 in the past two centuries, with salps being instrumental in this.

At the ocean surface, microscopic algae turn dissolved CO2 into organic carbon for energy. These algae are then consumed by many different animals, making them a vital part of the oceans’ food chain.

As this organic carbon is passed up through the food chain, much of it is respired and converted back into CO2, which is then released into the ocean and the atmosphere. However, some of this carbon is transported to the seafloor in the form of sinking parcels.

Just the beginning

One such deliverer of these parcels is the salp. When they ingest the algae at the ocean surface, they produce dense faecal pellets that rapidly sink to the seafloor, carrying large amounts of CO2.

However, during experiments conducted with NUI Galway’s collaborator, the Villefranche Ocean Observatory in France, the research team found that when salps ingested microplastics, the faecal pellets didn’t fall nearly as fast.

“Our study highlights that marine litter and microplastics may impact on animals and even ecosystems in ways we just haven’t considered yet,” said Dr Tom Doyle, senior author of the study.

“However, it is very important to point out that our study was carried out in a laboratory and under controlled conditions. We now need to go out into the field to further test our hypothesis by quantifying the abundance of microplastics found in salps and their faecal pellets in different areas of our oceans.”

Colm Gorey was a senior journalist with Silicon Republic