Ever since SEAPLEX was funded around two years ago, I have begun every one of my general audience talks (and even a few scientific ones) with a display of misleading and confusing headlines on the accumulation of trash in the North Pacific. According to these headlines, it’s twice the size of America, 3.5 billion …something…(they don’t say what), stretching from Hawaii to Japan. Most of these claims cannot be supported by any scientific data of which I’m aware.
As a scientist, it can be pretty frustrating to see these misconceptions repeated and repeated for years on end. That’s why the SEAPLEX team has done our best to accurately relay our observations from our own voyage to the North Pacific Central Gyre, and to refer people to reliable sources such as the NOAA Marine Debris Program’s FAQ. But I suspect the persistence of these misconceptions is why Oregon State University oceanographer Angelique White stated in a press release last week that the Great Pacific Garbage Patch is “grossly exaggerated.”
Since that press release and the ensuing media coverage, I’ve received many requests for clarification. If there’s no garbage patch, what the heck were we measuring back in 2009? But actually there’s no conflict between Dr. White’s statements and SEAPLEX findings. In this blog post, I’ll explain a few of the key points from the OSU press release.
“…it is simply inaccurate to state that plastic outweighs plankton, or that we have observed an exponential increase in plastic.”
Reports that plastic outweighs plankton stem from a 2001 study by Moore et al., published in Marine Pollution Bulletin. Most oceanographers, including myself, do not think that comparing the dry weight of plankton and plastic is a helpful way of understanding what is going on in the ocean. The reasons for this are somewhat technical, but you can read about them in this blog entry, which I wrote a year before I starting doing my own research on plastic in the North Pacific. I believe that this method is no longer much used – in a recent post at the Plastic Pollution Coalition’s blog, Marcus Eriksen of Algalita Marine Research writes “…it’s important to describe plastic to plankton ratios as an anecdote, but not worth quantifying.” Read his whole blog entry for the anti-plastic activist take on Dr. White’s press release.
As for an exponential increase in plastic, there is evidence that plastic debris increased from the 1960s and 1970s to the 1980s and 1990s. For example, a study by Robards et al. (1997) found more plastic in the stomachs of Arctic and subarctic seabirds in the late 1980s than between 1969-1977. After the mid-1980s, the trend becomes unclear. The only study of which I am aware that has measured this is Gilfillan et al. (2009). Using archived samples, they measured plastic in the California Current (not the gyre itself) in 1984, 1994, and 2007, and did not detect a significant increase.
“The studies have shown is that if you look at the actual area of the plastic itself, rather than the entire North Pacific subtropical gyre, the hypothetically “cohesive” plastic patch is actually less than 1 percent of the geographic size of Texas.”
In order to understand this, I emailed Dr. White directly, and she was happy to explain her calculations. First, remember that the vast majority, more than 90%, of the plastic found in the NPG are tiny – less than the size of your pinky fingernail. These pieces are spread out over the surface making them very hard to see with the naked eye. Mostly, the ocean just looks like ocean. In fact, here’s a photo I took smack in the middle of the “Eastern Garbage Patch” this fall:
But when you tow a fine-meshed plankton net through this same area, there are thousands of tiny plastic crumbs. They’re just really small, and fairly spread out on the surface of the ocean. Here’s a photo of the highest plastic densities I’ve ever seen in three trips to the Gyre, measured from a small boat on a glassy calm day. This is an area about the size of a dining room table.
So how can we reconcile finding plastic over 1,700 miles on SEAPLEX with Dr. White’s calculation that the “Great Pacific Garbage Patch” is just 1% of the state of Texas? There’s actually no conflict at all. Dr. White was looking at the area of the ocean’s surface covered by solid plastic, not where plastic pieces could be found. She calculated the area that would be covered by plastic if all tiny pieces were squished together into a solid “island.” Since the pieces are so small, that’s not very much area.
Many of the SEAPLEX scientists are considerably more concerned about the environmental impacts of these tiny pieces than we would be over a few larger pieces, or even a huge plastic island. There are many reasons for this, including toxins and the potential for such pieces to be ingested, but I think one of the most underrated impacts is the introduction of hard surfaces to an ecosystem that naturally has very few of them. Microbes, plants, and animals that live on hard surfaces are very different than those that live floating freely in the ocean, and adding all that plastic is providing habitat that would not naturally exist out there. To read more about our research, check out our webpage, or for a brief summary, this video podcast.
“If we were to filter the surface area of the ocean equivalent to a football field in waters having the highest concentration (of plastic) ever recorded…the amount of plastic recovered would not even extend to the 1-inch line.”
Once again, over 90% of the plastic pieces in the North Pacific Gyre are very small. There is no island, and the pieces are spread over the ocean’s surface. This photo of plastic and plankton collected on SEAPLEX represents an Olympic-sized swimming pool area of ocean (about 600 square meters).
When we painstakingly pick all that plastic out of the plankton samples, it is indeed a very small volume, only partially filling a container about the size of a nail polish jar (20 mL). However, in that tiny jar may be thousands and thousands of tiny pieces, collected in just 15 minutes of slowly towing a net along the ocean surfaces. Right now we don’t know what impact those pieces are having on the marine ecosystem, but we do know there are a lot of them, and that they can be found over a remarkably vast swathe of the North Pacific.
“Most plastics either sink or float,” White pointed out. “Plastic isn’t likely to be evenly distributed through the top 100 feet of the water column.”
This is true. Though we did find a few pieces of plastic at depth, most of the plastic that we observed on SEAPLEX was right on the ocean’s surface. Plenty of plastic debris has been found resting on the seafloor closer to shore – for example, one study conducted off central California found 6,900 pieces of debris per km2 (Watters et al 2010). I am not aware of any studies that have looked for plastic on the seafloor of the North Pacific Central Gyre – it’s pretty deep out there and considerable time and funds would be required.
Widespread misinformation, as is so common regarding plastic in the North Pacific, serves no one – not activists trying to ban plastic bags, not plastic manufacturers trying to develop ocean-degradable products, not groups developing methods to stop plastic pollution. Our role as scientists is to find out truths about the world, and to interpret and explain them. Debating what the data actually mean is a crucial part of the scientific process.
I think it is fantastic that so many groups and members of the public are passionate about what is happening in an obscure part of the ocean more than 1,000 miles away from any land. But the flip side of this interest is that the healthy scientific debate is going to be more public than usual. This is nothing to fear – in fact, I think it is a great window into how science is done. And I believe that this debate will ultimately be critical to finding a feasible solution to plastic pollution, whether than solution is based on land, at sea, or in legislative change.
Gilfillan, L., M. Ohman, M. Doyle, and W. Watson. 2009. Occurance of plastic micro-debris in the southern California Current system. CalCOFI Report 50. Retrieved from http://www.calcofi.org/publications/ccreports/251-vol50-2009.html.
Moore, C. J., S. L. Moore, M. K. Leecaster, and S. B. Weisberg. 2001. A comparison of plastic and plankton in the North Pacific central gyre. Marine Pollution Bulletin 42:1297-1300.
Robards, M. D., P. Gould, and J. Platt. 1997. The highest global concentrations and increased abundance of oceanic plastic debris in the North Pacific: evidence from seabirds. Pages 71-80 in Marine debris: sources, impact and solutions. Springer, New York.
Watters, D. L., M. M. Yoklavich, M. S. Love, and D. M. Schroeder. 2010. Assessing marine debris in deep seafloor habitats off California. Marine Pollution Bulletin 60:131-138. doi: 10.1016/j.marpolbul.2009.08.019.