As the true extent of the horrific levels of plastics that enter our oceans is finally being revealed, many are only now coming to understand the impact that this is having on marine wildlife. Most of this has focused on the fish and sea birds that have been found to consume the inorganic material, but little work has been done to assess how plastics affect those animals that live in the deep oceans.
Now research has found that one such deep-sea creature, the truly bizarre giant larvaceans, are chowing down on the plastic that sinks to the depths, and spreading it further and wider than before. These weird animals, which are effectively bags of pulsating mucus that drift around filtering particles out of the water column, are truly alien creatures.
The animal itself is shaped not unlike a tadpole, reaching roughly 10 centimeters (4 inches) in length, but they produce a sticky mucus filter that can reach up to a meter (3.3 feet) in size. They drift around the deep ocean, capturing food particles and passing them to a central mouth. But it now seems that they are also capturing tiny pieces of microplastic that also drift through the water, and could be playing an important role in moving the plastic through the deep sea and helping it settle on the deep seafloor.
“There's a lot of work being done studying plastic in the guts of seabirds and fish,” explained Kakani Katija, co-author of the paper published in Science Advances. “But no one has really looked at plastics in deeper water. We're currently working on experiments to study the concentrations of microplastics at different depths in the ocean, using water samples and maybe even cast-off larvacean houses.”
They have found that as the larvaceans filter out the suspected food particles, they also take in fragments of microplastics, and process them in the same way. They tested this by piloting remotely operated vehicles into the deep outfitted with containers of seawater and colored plastic microbeads. Once they found a larvacean, they released the microbeads, and then pulled back to watch what happened.
In 11 of the 25 larvaceans tested, the microbeads got caught in the mucus, and in six of these, they found that the animals were actually consuming the plastic. Following this, they poop out the tiny bits of plastic, which then rapidly sink to the ocean floor, and get mixed with the mud in the deep sea.
The fact that microplastics have been found even in the most remote and deepest reaches of the oceans has long puzzled researchers, and now this new discovery may help fill in the gaps as to how the plastics move around the oceans.