For years, scientists have been tracking a large accumulation of floating trash, mostly bits of plastic, in the north Pacific ocean called the "Great Pacific Garbage Patch," or the "trash vortex." This region, according to the latest research, has more lost and discarded plastic inside it than previous surveys suggested - like, a lot more. And it's still growing.
The Great Pacific Garbage Patch (GPGP) is filled with 79,000 metric tonnes (87,000 tons) of plastic, which is between 10 to 16 times higher than previous estimates, according to new research published today in Scientific Reports. Disturbingly, plastic pollution inside the GPGP "is increasing exponentially and at a faster rate than in surrounding waters," the authors state in the paper. For the many marine animals that make this vast ocean region their home, this is a dreadful development.
Mass concentration map using data pulled from the new survey. Image: The Ocean Cleanup
A popular misconception of the GPGP is that it's a gigantic floating island of plastic. In reality, it's a region of the north Pacific ocean, from Hawaii to California, that extends for 1.6 million square kilometers (618,000 square miles). In this region, floating garbage gets trapped by wind and ocean currents, where it's been steadily accumulating for decades. Looking at this region from a boat or plane, an observer wouldn't see very much or think that it's very polluted, but on closer inspection, the overall density of plastic garbage floating within it is high enough to warrant its designation as an area and phenomenon of concern. The new study, led by Laurent Lebreton from The Ocean Cleanup Foundation, was an effort to quantify and characterise the trash found within this major oceanic "plastic pollution hotspot," also known as an oceanic gyre.
"Plastic accumulates in this region because of converging currents and low sea surface wind," Lebreton explained to Gizmodo. "This is a natural phenomenon that occurs in subtropical waters of every oceanic basins in the world. There are actually four other accumulation zones such as this one: South Pacific, North Atlantic, South Atlantic, and Indian Ocean."
Nets collecting plastic.Photo: The Ocean Cleanup
From July 27th to September 19th, 2015, Lebreton's team surveyed the GPGP using aerial surveys and data collected by 652 nets pulled by 18 ships. The aerial images offered a more accurate assessment of the debris than previous surveys, which relied exclusively on visual surveys taken from boats.
A "ghost net" lifted aboard a survey ship. Photo: The Ocean Cleanup
"Plastics were by far the most dominant type of marine litter found, representing more than 99.9 per cent of the 1,136,145 pieces and 668 kg [1,473 lbs] of floating debris collected by our trawls," write the authors in the new study. Over three-quarters of the collected plastic was larger than two inches (5 cm), and nearly half came from fishing nets. Microplastics, measuring less than five millimetres in length (about the size of a sesame seed), represented 8 per cent of the total mass of the GPGP - but microplastics account for a whopping 94 per cent of the estimated 1.8 trillion pieces of floating debris within the patch.
"We knew most pieces are comprised of microplastics; however, when you look at the total available mass of plastic, most material is contained in large debris that may degrade into harmful microplastics over time," said Lebreton.
Claudia Halsband, a senior scientist at Akvaplan Niva who isn't affiliated with the new study, says this observation make sense - that the smaller the size range that is included in such surveys, the more particles are found. "This is expected as one piece of macroplastics can degrade into thousands if not millions of microplastics, hence the discrepancy between their contribution to mass versus abundance," she told Gizmodo.
Only certain types of plastic can float and collect within the patch, namely polyethylene and polypropylene, which are typically used in packaging. Most of the plastic had broken down into indistinguishable bits and pieces, but items that were identifiable included containers, bottles, lids, packaging straps, ropes, and fishing nets. Some items even had the date of production stamped onto them, the oldest dating all the way back to the 1970s.
A sample of the plastic waste collected during the survey.Photo: The Ocean Cleanup
Disturbingly, the estimates of plastic within the patch may actually be too low.
"We used conservative methods whether in sampling or modelling during our research," Lebreton told Gizmodo. "For instance, take the aerial expedition data, when we were not sure if a spotted debris was plastic or something else (e.g. organic debris, wave chops, sun glints or marine life), we decided not to log the sighting so we were conservative."
In terms of why the new estimate was so much higher than those produced by previous surveys, the researchers say it likely has to do with improved survey techniques, but also increasing levels of ocean plastic pollution. Each year, anywhere from 5 million to 19 million tonnes (5.5 to 20.1 million tons) of plastic is dumped, either intentionally in inadvertently, into the ocean. The spike may also have something to do with the 2011 earthquake and tsunami in Japan, which washed an estimated 4.5 million tonnes (5 million tons) of debris into the ocean in an instant, of which 70 per cent may have sunk rapidly to the bottom. The next steps for the researchers, and others concerned with this growing patch, is to figure out the primary sources of all this ocean plastic, and to determine how long plastics stay with the area.
"This is an impressive and important study," Matthew Savoca, a postdoctoral researcher at NOAA's Southwest Fisheries Science Center, told Gizmodo. "I have been hearing whispers about this study for a while now, so I was excited to read it, and it did not disappoint." Savoca said the new results were "sad but not terribly surprising" when considering the team's thorough approach to measuring large plastic debris at such an enormous scale. "Counterintuitively, larger plastic has been more difficult to quantify than microplastics in the open ocean, so this study fills an important knowledge gap in that respect," he said.
Needless to say, the size and density of the GPGP is bad news for marine life, as animals like sea turtles and marine mammals can get tangled up in abandoned fishing gear and starve or drown — a phenomenon known as "ghost fishing." Based on the new data, Savoca says this is a more serious threat to ocean life than previously considered. Another problem is that "hundreds of species of marine wildlife consume plastic, which has negative effects on those animals including malnutrition and biomagnification of plastic-derived toxicants," said Savoca. This could eventually be a concern for human health if we start to eat fish that have consumed plastic. "Finally, more recent studies suggest that plastics may harbour pathogens and introduce disease to wildlife that is immunologically unprepared for this microscopic onslaught," he said.
As a biologist, Halsband said she's most concerned about the smallest particles, "not only because they are the most abundant, but because they interact with the smallest organisms at the base of marine food webs (such as zooplankton), and the potential for a magnification of the impacts up the food chain is high," she told Gizmodo.
While discouraging, Savoca says there is a silver lining to the study.
"As with CFCs and the ozone hole in the 1980s, with this issue - plastics in the ocean - we have identified the problem, the cause, and potential solutions," he said. "There are things people can do everyday to help mitigate this issue, including supporting environmentally friendly legislation and reducing your own dependency on single-use plastics." For example, we can politely refuse plastic straws in restaurants, plastic cups on aeroplanes, or plastic coffee lids at Starbucks. "Who needs that stuff anyway!" said Savoca.