Scientists find plastics at bottom of deep submarine canyon

University College Cork scientists have discovered plastic at the bottom of a deep submarine canyon at 2,125m water depth while investigating cold-water coral habitats on board the Marine Institute's RV Celtic Explorer.

UCC's Marine Geology Research group has been investigating cold-water coral habitats in the Porcupine Bank Canyon, some 320 km due west of Dingle, on a research expedition led by UCC's Dr Aaron Lim.

Scientists have recovered eight novel monitoring stations called 'landers' worth €450,000, deployed between 2,500m water depth and 700m water depth by the Marine Institute's Remotely Operated Vehicle (ROV) Holland 1, earlier this summer.

The monitoring stations record the speed, temperatures and direction of the currents around these habitats as well as trapping samples of the food, sediments and microplastics being deposited around the corals to understand conditions and how the corals are coping with changing oceans.

The researchers found plastic in the bottom of the canyon at 2,125m water depth, as deep as ten Eiffel Towers stacked on top of one another. The reach of human plastic waste is down this deep, even 320km offshore.

"It's always sad to see plastic rubbish in these otherwise pristine habitats. It is quite incredible that our plastic waste can get this far out and so deep in the oceans," said UCC Professor Andy Wheeler, who has pioneered research on cold-water coral mound offshore Ireland over the past 20 years.

"I don't think people think about this when they dump their rubbish. We're also trying to see if microplastics are being fed to the corals from above. We've just got the samples, let's hope we're wrong."

The Porcupine Bank Canyon, which is deep enough to stack ten Eiffel Towers inside, is teeming with a whole range of cold-water coral habitats, just on Ireland's doorstep, according to Dr Lim.

"The environment is much more dynamic than we thought, with two of the monitoring stations knocked over by the currents; food supply for the coral is variable but the corals are doing okay. Some of these habitats have existed for millions of years and have grown so large they resemble hills made of coral, called coral mounds.

This is the first time eight of these monitoring stations have been deployed and collected using the ROV Holland 1. It will provide scientists with an insight into the processes affecting these cold-water coral habitats, food sources and the impact of microplastics.

Ireland's cold-water coral reefs are found in the cold, dark ocean at water depths of 600m to 1,000m along our continental margin. "Not only is this expedition vital for understanding these habitats and our impact upon them, it also acts as a baseline to start monitoring how our deep-water habitats here are changing," added Dr Lim.

The team has a research agenda which will see them return to the canyon and other habitats alike for a number of years to monitor the changes in the environment around these habitats. The monitoring stations will be brought back to UCC for detailed analyses.

This research survey is carried out with the support of the Marine Institute, funded under the Marine Research Programme 2014-2020 by the Irish Government to support and promote the Atlantic Ocean Research Alliance (AORA). AORA facilitates common research and knowledge exchange for us to provide healthy, resilient oceans for our future generations.

The survey has also received funding from Science Foundation Ireland, Geological Survey Ireland and University College Cork.

ENDS