There is a lot of trash in the ocean, but apparently there is not enough.
Humanity produces and throws away astounding amounts of plastic every year, so researchers expected to see similarly large amounts floating around in the oceans. Any floating debris travels and groups into larger collections due to the oceans' currents.
Researchers expected to find about a million tons based on data that has been collected for the past 30 years. But the results of a study from the University of Cadiz in Spain showed only 7,000 to 35,000 tons of plastic trash floating in the ocean.
The problem with finding less trash than expected is that we don't know where the rest is located. The possible explanations are all troubling.
The researchers analyzed data from multiple collection trips, including a cruise (the Malaspina expedition) that circumnavigated the world and collected garbage at 141 locations with a mesh net. In total, 313 sites were examined in the Indian, Pacific and Atlantic Oceans. The debris contained pieces of polyethylene and polypropylene products such as bags, food containers, toys and utensils.
The results were analyzed by a team of researchers led by Andrés Cózar, and published in the Proceedings of the National Academy of Sciences of the United States of America. This is the first time measurements of floating trash have been collected and combined to produce a worldwide assessment.
One explanation for why less floating plastic was found is that much of the debris breaks into semi-microscopic pieces. These pieces would then enter the food chain when swallowed and digested by small marine organisms, which are then preyed on by larger organisms that often end up on our plates.
"Ocean currents carry plastic objects which split into smaller and smaller fragments due to solar radiation. Those little pieces of plastic, known as microplastics, can last hundreds of years," says Cózar.
Another proposed explanation is that the plastic debris that was not found already sank down to the deeper, less-explored depths of the ocean. The ocean floors still contain unsolved mysteries but if chunks of synthetic material are landing in the deep ocean, the environment down there will be modified.
The final explanation offered, but the most unlikely, according to researchers, is that some of the smaller pieces of the plastic debris might be washing ashore.
The study says, "Resolving the fate of the missing plastic debris is of fundamental importance to determine the nature and significance of the impacts of plastic pollution in the ocean."
