The plastic poured into the sea releases organic compounds that stimulate the growth of marine bacteria, according to a recent study. The research, published in the journal Nature Communications, reveals that the plastic waste releases up to 23,600 metric tons of organic carbon dissolved in water, which is mostly consumed by bacteria which multiply faster.
The study, carried out during the last two years by Spanish researchers in collaboration with the University of Vienna, Austria, has focused on how plastic waste discharged into the oceans affects the lowest levels of the food chain, the bacteria.
The team conducted their experiments using different types of plastic that are floating in the oceans’ waters and exposed them to solar radiation for periods between a week and a month. They used the exact same types of plastic that are found in greater proportion in the ocean, such as high and low-density polyethylene and polypropylene.
The researchers observed that all the studied plastic waste released organic carbon, whether they had been exposed to solar radiation or not.
Taking into account that each year up to 12 billion tons of plastic are dumped into the ocean, the study’s results suggest that this plastic is annually releasing 23,600 metric tons of organic carbon.
In the second phase of the study, the scientists added bacteria into the equation
Researchers observed that, after only five days, the bacteria had consumed 60% of the dissolved organic carbon released by the plastic waste. In addition, in cases where the plastic had not previously been exposed to solar radiation, the bacteria consumed more carbon and grew more rapidly.
“This indicates that solar radiation produces structural changes in the compounds released by the plastic, which can inhibit the growth of bacteria,” according to Alvarez Salgado, one of the researchers.
Scientists estimate that more than five billion pieces of plastic are currently floating on the surface of the oceans and forecasts indicate that the marine plastic waste that is discharged will increase up to 10 times in the next decade. This will proportionally increase the amount of organic carbon, with consequences for bacteria growth and, in turn, for other aquatic organisms and for the carbon cycle in the oceans.