Scientists have a new way to estimate how often ocean animals get tangled in plastic — and it could explain why so many whales are washing up dead

  • An average of about 8 million tons of plastic enters the ocean as pollution annually, though the maximum amount could be closer to 14 million tons.
  • Whales and other marine animals can confuse plastic items for food and consume them, or get entangled in plastic nets. This can lead to strangulation and death.
  • A new study shows that the amount of plastic in the North Atlantic Ocean has increased dramatically since the 1990s, and the number of plastic entanglements increased 10-fold between 2000 and 2016.

For six decades, a research device with a rather unsexy name as been roaming the North Atlantic Ocean, pulled behind ships by a thick metal wire.

Called the Continuous Plankton Recorder (CPR), the three-foot-long metal torpedo’s original purpose was to collect plankton samples that give scientists clues about the quality of ocean water. But in 1957, the recorder got snagged in some trawl twine off the coast of Iceland. Eight years later, a plastic bag ensnared the CPR near Ireland.

The two ominous incidents were recorded in the CPR’s handwritten logbooks, early signs of a problem that’s now well known: The oceans are filling up with plastic.

“It’s fascinating to think that someone would have recorded that in a logbook not knowing that now it’d be an issue,” Clare Ostle, the author of a new study about plastic in the ocean, told Business Insider.

Some 165 million tons of plastic are currently circulating in Earth’s marine environments, according to the Ocean Conservancy. Ostle’s study, published in the journal Nature Communications, analysed old CPR logbooks in order to tabulate where and how often plastics like fishing nets became entangled in the torpedo. Since 1957, her work showed, the CPR ran afoul of plastic trash 669 times.

Most of those encounters happened between 2000 and 2016 – the number of entanglements increased 10-fold over that 16-year period, according to Ostle’s analysis.

Discarded nets and fishing lines ensnare the CPR

The CPR gets dragged by ships, and is designed to cut its way through the top 20 feet of the ocean, undulating to the surface and back down much like a whale or sea turtle would. The device debuted in 1931, and has travelled over 6.5 million nautical miles since 1957.

CPR trawlMarine Biological Association/Courtesy of Clare OstleSince 1957, the Continuous Plankton Recorder (CPR) has been towed over 6.5 million nautical miles in the North Atlantic and adjacent seas.

As the topic of plastic pollution has gained traction in recent years, Ostle said, her research team wondered what else they could do with the plankton recorder and its data.

“We spoke to ship employees who dragged the recorder, and they complained about more entanglements,” she said.

So Ostle and her co-authors set about tracking down every instance that the CPR got mixed up with plastics, and collated the data from the past six decades. According to the records, the number of entanglements has been increasing since 1957, and about 4% of the CPR’s 16,725 trips through the ocean involved running into some type of plastic (a total of 669 encounters).

Most snarls – 55% – were caused by discarded nets and fishing lines. Plastic bags accounted for about 10%, while nylon, string, and other miscellaneous plastics accounted for the rest.

The CPR data showed that most plastic entanglements occurred in areas with high fishing activity, with the most recorded in the southern North Sea between the UK and Norway.

Ostle and her colleagues’ analysis follows up on a 2004 study that used CPR data to count the amount of microplastics (tiny pieces of plastic smaller than half a centimeter) found in the North Atlantic Ocean and nearby seas since 1960. Those older results, unsurprisingly, indicated that the quantity of microplastics more than doubled from the 1970s to the 1980s, mirroring an increase in worldwide production of synthetic plastic fibres during that time period.

Ostle said her new study confirms a trend scientists knew about but hadn’t been able to show with data: The amount of large plastics in the open ocean has been increasing since the 1990s, too.

The plastic pollution problem

Given that ships pulled the intrepid CPR through the depths at which whales and other marine mammals typically surface, the researchers believe that this study can serve as a decent way to estimate the increasing rate of animal entanglements, too.

According to a 2014 report from the National Oceanic and Atmospheric Administration (NOAA), marine entanglements affect at least 200 species around the globe. More than 100,000 marine mammals get entangled in plastic bags and die annually.

On average, about 8 million tons of plastic enters the ocean every year, though the maximum amount could be closer to 14 million tons.


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Shoppers worldwide use some 500 billion (yes, billion) single-use plastic bags annually. That’s roughly 150 bags per year for every person on Earth, according to the nonprofit group Ocean Crusaders. Strung end-to-end, that would be enough plastic to circle the globe 4,200 times.

These bags typically end up in landfills or in the sea, where they wind up collecting in certain parts of the ocean, along with straws and microplastics. The largest of these trash-filled vortices, the Great Pacific Garbage Patch, is more than twice the size of Texas, though there’s another giant patch in the North Atlantic.

Whales and other marine animals appear to be consuming this plastic, which can lead them to change their behaviour, get strangled, and die.

Recently, a pregnant sperm whale washed up dead on the shores of Sardinia with nearly 50 pounds of plastic in its stomach. Less than a month earlier, another dead whale was found to have ingested 88 pounds of plastic.


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A pregnant sperm whale was found dead with nearly 50 pounds of plastic in its belly

“The main thing to take away here is this increase in plastics is happening,” Ostle said. “We are seeing it and need to focus on the things like fishing lines and nets that are most damaging.”

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