Microplastic Pollution in the Southern Ocean: Finding What Lies Beneath the Surface

EarthzineWriting Fellowship 2017

Sometimes at-sea research requires trips to land for sampling. Image Credit: Giuseppe Suaria

Plastic pollution is choking the world’s oceans. Scientists have been monitoring the presence of large pieces of plastic on the Antarctic continent for more than 30 years. Plastic ingestion detected in Southern Ocean seabirds signaled its presence in this region as well. However, little is known of the extent of the pollution in Southern Ocean waters, either on the surface or just below it.

Scientists aimed to change that, and recently completed a journey of a lifetime to quantify plastic marine debris in the Southern Ocean waters surrounding the Antarctic continent.

The expedition encountered fierce ocean conditions, including the ice sheets of the Antarctic continent. Image Credit: Giuseppe Suaria

From December 2016 to March 2017, a team from Swiss Polar Institute completed the Antarctic Circumnavigation Expedition (ACE) on board the Akademik Tryoshnikov, an icebreaker outfitted for scientific research. The vessel traveled from Germany to Cape Town, and then completed a circuit around the Antarctic continent before returning north. The expedition comprised 159 marine and terrestrial researchers from around the world working in diverse scientific fields, all curious to find out more about Subantarctic ecosystems.

It was no easy task. The team quickly discovered that standardized methods of surveying for plastic pollution would not stand up to the fierce Southern Ocean currents surrounding Antarctica. Rough seas in the Southern Ocean made it difficult to see anything floating on the surface during surveys, or safely use nets and trawls to collect samples without damaging the equipment and endangering the crew. So, expedition researchers developed new and groundbreaking survey methods to more precisely track plastic pollution, particularly microplastic pollution, in the Southern Ocean.

Some of the wild and stunning Antarctic residents. Image Credit: Giuseppe Suaria

Giuseppe Suaria is a research fellow with CNR-ISMAR (Consiglio Nazionale delle Ricerche – Istituto di Scienze Marine) in Italy. Plastic marine debris is Suaria’s specialty. He surveys the ocean surface and what lies beneath the surface for litter (or debris). In 2016, he authored a paper that alerted the world to the “plastic soup” polluting the Mediterranean Sea.

Having never been to Antarctica before, ACE was a new adventure for him. He said some days left him “completely speechless with the beauty of the places we visited. They were wild, wonderful, amazing, and stunning.”

Peter Ryan, the other lead scientist in this endeavor, was a little more familiar with the Southern Hemisphere as director at the Percy FitzPatrick Institute of African Ornithology, University of Cape Town, South Africa. Ryan has been investigating the impacts of plastic marine debris on seabirds in the Southern Hemisphere since the 1980s.

Ryan and Suaria collecting samples on land. Image Credit: Patti Virtue

Plastic pollution poses entanglement and ingestion risks to marine organisms, and can transfer harmful pollutants to marine ecosystems. Plastic pollution includes microplastics, which are tiny pieces of plastic less than 5 mm across. While it is accepted that microplastic pollution is distributed across the globe, scientists are only just starting to understand the full extent of how microplastics impact the environment. Antarctic researchers did not think microplastics could penetrate the Southern Ocean, which is guarded by the Antarctic Circumpolar Current, but the work by Suaria and Ryan may prove otherwise.

Suaria, Ryan, and the ACE researchers wanted to quantify how much plastic debris was floating on the surface of the Southern Ocean; they also were eager to understand how much plastic debris was distributed through the upper water column.

According to Ryan, it was an interesting cycle of discovery, because while scientists are certain that plastic pollutes all corners of the planet, knowing the quantity and types of plastic pollution in all regions is critical in the development of ocean pollution mitigation plans.

A bongo net was used to filter water samples and catch solid objects on a mesh screen. Image Credit: Giuseppe Suaria

Traditionally, standard methods of tracking and quantifying plastic pollution entail at-sea surveys of the ocean surface for litter that could be detected with the naked eye from the bow of the ship. Another method involves filtration systems, such as neuston trawls and bongo nets, to filter ocean water through a fine mesh net, catching solid objects; this was the original methodology Suaria and Ryan intended to use.

However, in the Southern Ocean, these standard methods for surveying plastic pollution turned out not to be enough to detect its presence and reliably quantify it. Ryan conducted thousands of kilometers of surveys and counted less than 22 items floating in the Southern Ocean.

They suspected that these surveys were not capturing the full picture. “At first, we thought that we were sailing through, fortunately, the last very clean ocean of the world, and the overall impression was that we were in a pristine sea, it was pretty good,” said Suaria. “Overall, we saw very few floating items, or macro debris.”

Something was missing. According to Suaria, plastic was everywhere, and in massive numbers, even though they couldn’t see it from the bow of a boat.

Scientists aboard ACE also traveled to land via helicopter. Image Credit: Giuseppe Suaria

“It was a special moment when we realized that the Southern Ocean was not as clean as we were thinking,” Suaria said. “We started collecting samples in a slightly different way and that’s when we realized … we were missing something really big.”

This is where Tommy Bornman comes in. Bornman is the manager of the Elwandle Coastal Node of the South African Environmental Observation Network and led the plankton sampling team. The rough seas prevented his team from deploying their bongo nets to sample plankton, so they resorted to filtering water from the ship’s intake system, drawn from 5 meters underwater. Occasional synthetic-looking fibers were collecting on the filters in the intake system, which Bornman reported to Suaria. Ryan said he believed the fibers were probably contamination from either the air in the lab, or from effluent water from the washing machines aboard.

But Suaria and Bornman persisted, insisting that it was possible the fibers were in the ocean itself. Ryan devised a plan to sample the waters ahead of the ship (so as to avoid contamination from the ship). They found more synthetic fibers than expected.

“Everybody became immediately aware that we were in front of something really unexpected and big,” said Suaria.

Leveraging the diverse research specialties of the researchers present on the boat, Suaria and Ryan sought to develop a new approach in collaboration with the plankton sampling crew.

As they dug deeper, looking more closely for items like microplastics, instead of the items that were visible from the surface, the amount of microplastic pollution they discovered was more than they had anticipated. This countered previous beliefs that the waters surrounding Antarctica were somewhat protected by the fierce Southern Ocean currents circling the continent.

As ACE concluded and data analysis began, Suaria felt a sense of urgency to disseminate this newly discovered knowledge to the world. Over the past year, he has been characterizing all the items he found in his sample collections.

Suaria and Ryan presented preliminary results of research at the 6th International Marine Debris Conference in San Diego, California.

Suaria’s and Ryan’s discovery of more microplastics exceeded what was previously believed to exist in the Southern Ocean.  This was one of the most valuable research outcomes of ACE.

“The world needs to know we are devastating the last wilderness. It’s not so pristine anymore,” said Suaria.

Veronica Padula, a 2017 Earthzine writing fellow, is working on her Ph.D. in fisheries at the University of Alaska Fairbanks College of Fisheries and Ocean Sciences. Padula is STEM program manager for the Aleut Community of St. Paul Island.