The pollution of our oceans of oceans by marine litter and microplastics could be having an even worse affect on the environment than previously feared.
A new study led by marine scientists from the Ryan Institute at NUI Galway in collaboration with UCC and Villefranche sur Mer Laboratory has found that microplastic pollution may be having a serious impact on the systems in the ocean that absorb carbon dioxide from the atmosphere.
The NUIG research team looked at how microplastics affect small, jellyfish like creatures called Salps that play an important role in uptake of carbon dioxide from the atmosphere and its transport to the sea floor where it is stored.
The ocean is the single largest natural absorber of Carbon Dioxide emitted through the burning of fossil fuels, where it plays an important part in the marine ecosystem.
At the sea surface, microscopic algae turn dissolved CO2 into fuel (organic carbon). These algae are consumed by many different animals and form the basis of the marine foodweb.
However, as it passes through the food chain much of that carbon is respired and converted back into CO2 to be emitted into the atmosphere once again.
This is where Salps play an important role. They eat the algae on the sea surface and instead of re-emitting it they produce dense faecal pellets, which rapidly sink to the deep sea, carrying with them some of this captured carbon.
“Our oceans are estimated to have captured one quarter to one half of all human-derived carbon dioxide from the atmosphere in the last two centuries,” said lead author of the study Alina Wiczorek from the Ryan Institute.
She added that the “downward transport of carbon by salps and other zooplankton animals accounts for a major portion of this.”
Laboratory experiments carried out at the Villefranche Ocean Observatory found that when salps ingest microplastics and incorporated them into their faecal pellets they did not sink as fast anymore.
According to Alina Wieczorek, as the faecel pellets stay near the surface for longer “they may get broken down causing the carbon dioxide to be re-released back into the ocean and atmosphere”.
This mean that microplastic pollution could be driving down the efficiency of one of the most crucial natural processes for absorbing carbon dioxide.
The research team also noted that even when the faeces does sink, it carries the microplastic with it doe the deep ocean, further spreading human pollution.
Recent findings of plastic pollution in the Marian Trench, the single deepest point in the ocean on earth, supports these fears.