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The Bay of BengalA recent study has found that 88 percent of the ocean contains plastic debris. Yet despite this wide diffusion, a vast amount of plastic is still unaccounted for.

In 2010, the Malaspina expedition used four ships to trawl the five garbage gyres of the world’s oceans. Pulled by winds and ocean currents, debris is swept into these gyres to become floating islands of – mostly plastic – trash. For months, researchers with the Malaspina trailed these gyres with fine mesh nets. Using their data, as well as regional surveys and previously unpublished reports, the team eventually calculated that the ocean contains about 40,000 tons of plastic.

Plastic does not biodegrade. Instead, solar radiation and salt water break it into smaller and smaller pieces. “Those little pieces of plastic, known as microplastics, can last hundreds of years,” says lead researcher Andres Cozar from the University of Cadiz. Microplastics “were detected in 88 per cent of the ocean surface sampled during the Malaspina Expedition 2010.”

While 40,000 tons seems like a lot, previous estimates of plastic diffusion led the Malaspina team to assume a much higher volume. In the abstract to their study, they note that, “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.”

Every year, humans produce about 300 million tons of plastic. Most of that goes into landfills but a small percentage of it is carried or dumped into the ocean. While some of it ends up trapped in Arctic ice (and more than previously suspected), most of it remains unaccounted for. Carlos Duarte, an oceanographer at the University of Western Australia and a member of the Malaspina team, says, “We can’t account for 99 percent of the plastic that we have in the ocean.”

Both Duarte and oceanographer Peter Davison believe fish are eating it. In what quantities, they’re not sure, and neither is certain what effect that has on the marine ecosystem. “Yes, animals are eating it,” says Davison. Toxins such as DDT, PCBs and mercury can adsorb into the microplastic and enter fish, potentially harming the food chain. Yet once consumed by the fish, those toxins, “may dissolve back into the water…or for all we know they’re puking it or pooping it out, and there’s no long-term damage. We don’t know.”

According to experts, the missing plastic may be degrading into pieces too small to detect, organisms may be latching onto them and pulling them below the surface, or microbes may even be eating them. No oceanographer or marine biologist is certain. All agree that more research is needed.

Update 12.26.2014 – In December, the 5 Gyres Institute released the first-ever complete global estimate of ocean plastic pollution. In their ‘All Gyres Paper,’ their researchers found that the ocean contains some 5.25 trillion plastic particles weighing over 268,000 tons. Planet Experts editor-in-chief, Pierce Nahigyan, spoke to 5 Gyres co-founder Marcus Eriksen on the report.

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