Researchers from University College Cork have found plastic on the seafloor at depths of more than 2km where even light has never penetrated.
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 on board the Marine Institute’s RV Celtic Explorer.
The group has 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 some three months ago.
While the monitoring stations record the speed, temperatures and direction of the currents around these habitats, it has also trapped samples of the food, sediments and microplastics, indicating the reach of human pollution on the darkened seabed.
Evidence of plastic was found at 2125m water depth - deep enough that you could stack 10 Eiffel Towers inside.
UCC Professor Andrew Wheeler said work was continuing to analyse samples brought up from the canyon, which will look at the potential impact of plastic on marine life at those depths.
"We felt the public would be shocked and surprised that plastic could end up 300km from the Irish coast and 2km down," he said.
Humans rarely visit here and yet their waste is there.
There are concerns about what impact plastic at those depths might have on marine life, particularly when plastic degrades to become microplastics. In the canyon dead plankton is a fundamental foodstuff for marine life, yet one fear is that plankton ingesting microplastics could increase buoyancy, potentially starving life at greater depths.
"We are in a position where our planet is changing rapidly and we have to be concerned about that," Prof Wheeler said.
Dr Lim said: “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 OK. 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. Dr Lim said: “Not only is this expedition vital for understanding these habitats and our impact upon them, but it also acts as a baseline to start monitoring how our deep-water habitats here are changing."
The research team agenda will return to the canyon and other habitats for a number of years to monitor the changes in the environment around these habitats, with the monitoring stations brought back to UCC for detailed analyses.
Paddy O’Driscoll, ROV Holland I superintendent, said: “It’s great that Ireland now has the technological capacity to undertake surveys in the deep seas and answer questions not just for Ireland but also vital to understand our planet’s health."
The research survey is supported by the Marine Institute, funded under the Marine Research Programme 2014-2020 by the Irish Government, and by Science Foundation Ireland, Geological Survey Ireland and University College Cork.