A study published on Wednesday estimates that the ocean contains over 260,000 tons, or 5.25 trillion pieces, of plastic. The study found that the amount of microplastics, pieces of plastic that are less than half a centimeter, found on the ocean's surface were much smaller than expected.
The study was conducted by Marcus Eriksen of the Five Gyres Institute, which works to reduce plastic pollution.
Eriksen took data from 24 different ocean expeditions in major ocean currents across more than 1700 different locations. The researchers ran their data through a model to produce estimates for the amount of plastic of various sizes in the ocean. According to the researchers, all of their estimates are "highly conservative, and may be considered minimum estimates." Indeed, their projections account for only 0.1 percent of the world's annual plastic production.
Over 90 percent of the searches that the study did contained plastic, and polystyrene made up most of the plastics found. One of the researchers said that in some areas with larger amounts of debris, there was more plastic in the water than living creatures. The amount of plastic found in the northern and southern hemispheres were about the same, which the study's authors said was surprising "given that inputs are substantially higher in the northern than in the southern hemisphere." The authors said that this might mean that plastic pollution moves between different oceans more easily than previously assumed.
The study's authors said that "removal processes" such as UV degradation, consumption by organisms and loss of buoyancy are responsible for the low amounts of microplastic found on the ocean's surface. The Five Gyres Institute explains that forces such as waves and sunlight break plastic down into smaller pieces but that the plastic never fully disappears.
According to The New York Times, the fact that there were fewer pieces of microplastics than expected is not good news. These pieces of microplastics could have settled deeper into the ocean or along the sea floor, where recovering and cleaning them up is more difficult. In addition, plastics can become coated with other pollutants, so when organisms eat them, they consume additional toxins. Fully 44 percent of seabirds and all sea turtle species have been found with plastic in their bodies, and studies have shown that sea organisms consume plastic at rates higher than previously thought.