The first thing to know about marine plastic waste is that most of what you may already know is wrong. There isn’t really a “great garbage patch” in the Pacific, or any other ocean–in the sense that a patch is a physical thing that you can see. It doesn’t look like an “island” (unless you have a funny idea of an island). And it isn’t the size of Texas.
So, what is it really? By the time plastic ends up in the middle of the ocean, most of it has been ground down into small, “mircoplastic”-sized pieces and is suspended below the water surface. Though there is trash floating on the surface, it’s not a significant part of the total, even in ocean gyres where bottles and packaging collect.
How much plastic is in the oceans in all? Estimates of the total plastic product weight that has entered the ocean are in the range of millions of tons. But sample collections show only a small percentage of the probable total. The 2010 Malaspina Expedition, a big ocean research project, found plastic over wide areas, but, overall, far less than researchers thought they’d find. For reasons that aren’t fully understood, most of the plastic had disappeared.
In the 2010 expedition, researchers took about 200,000 samples at 313 points in the Indian, Pacific, and Atlantic Oceans, at depths up to 6,000 meters. They identified microplastics in 88% of ocean surface that was surveyed. But the yield equated to tens of thousands of tons in total, not thousands of thousands as projected. “The global load of plastic on the open ocean surface was estimated to be on the order of tens of thousands of tons, far less than expected,” the scientists write in a study reporting the work.
Lead author, Andrés Cózar, a researcher from the University of Cadiz, says there are several possible explanations. “We propose the existence of processes efficiently removing floating plastic from the surface,” he writes in an email. “This sink may involve a combination of fast nano-fragmentation of the microplastic into particles of microns, or smaller, their transference to the ocean interior by food webs and ballasting processes, and processes yet to be discovered.”
In translation: Possibilities include that the plastic is broken into pieces too small be captured by nets, that it accumulates on coastlines (the Malaspina was only on the open sea), and that the plastic becomes dirty and sinks to the bottom. Or that it’s being eaten by fish. “There are signs to suggest that plankton eaters are important conduits for plastic pollution and associated contaminants,” Cózar says.
That’s not to say, the marine plastic problem isn’t as large as thought. It’s just different–less visible and less understood–than we thought. “Many descriptions of the plastic garbage patches have not been accurate, using pictures don’t illustrate the problem,” Cózar says. “These plastic accumulations aren’t islands. But, it is evident we are putting too much plastic into the oceans, and that we don’t know what this plastic is doing.”