A lot of data showing when the Atlantic started drowning with plastic has been discovered in manuscript log books from a little-known but persistently persistent plankton study dating back to the middle of the last century.
From the fishing line found in the ocean in the 50s, then in a first transport bag in 1965, it reflects how the problem of marine debris grew from small incidents, largely ignored, to becoming a issue of global concern.
The unique data set, published in Nature Communications, is based on the records of the continuous plankton recorder, a torpedo-shaped marine sampling device that has been towed along more than 6.5 m of nautical miles from the ocean during the last 60 years.
Based initially on Hull, then on Edinburgh and Plymouth, the long-duration program was initially designed to collect pelagic plankton, which is an indicator of water quality and also a source of food for whales and other marine species.
But operators have also kept track of the entanglements that interrupted their work: what caught the team, where it happened and when. This has proven to be a valuable source of data on plastic waste, according to contemporary researchers.
"This consistent time series provides some of the first records of plastic entanglement, and is the first to confirm a significant increase in plastics in the open sea in recent decades," the document said.
The beginning of the problem was so slow that it hardly noticed. The record shows strands of fishing line found on the east coast of Iceland in 1957, and then a transport bag in waters northwest of Ireland eight years later. The document states that this was a couple of years before the first reports of turtles and seabirds that had been trapped in the plastic.
During the following decades the problem grew constantly. In the 50s, 60s and 70s, less than 1% of the trailers were interrupted by entanglements with synthetic materials. For the 90s it was almost 2%, and in the first decade of this century the increase "was of an order of magnitude", according to the newspaper. The figure is now hovering between 3% and 4%.
Almost half of the interruptions are caused by discarded nets, lines and other fishing equipment. Other plastic objects account for the rest. The document said that this highlighted the dangers to marine life because the sampling device was towed by ferries and container ships to a depth of approximately 7 meters, where many fish and marine mammals can be found. The number of entanglements was particularly high in the southern North Sea, but the authors said the problem was evident in a wide variety of oceans.
Clare Ostle, of the Marine Biology Association based in Plymouth, said: "The message is that marine plastic has increased significantly and we are seeing it all over the world, even in places where we would not want to do it, such as the Northwest Pbadage and other parts of the Arctic. "
He was encouraged that the number of transport bags hooked by the team seemed to have stabilized in recent years, and he speculated that this could be the result of greater consumer awareness. But he cautioned that the data did not have a precise correlation with the amount of plastic in the ocean and that it looked better as a guide to general trends.
This is the second time that the continuous plankton recorder provides essential data on marine plastic. Since 2004, the samples were badyzed retrospectively to detect microplastics, which revealed a significant increase from 1960-70 to 1980-1990.
Ostle said the plankton recorder, which has been running since 1931, continued to produce important new data because it offered a longer timeline than more sophisticated studies.
"I was inspired by the story, the legacy of all the people involved," he said. "It's impressive when you consider how they have maintained it for so long in the face of many challenges."
The sampling operation almost collapsed as a result of government cuts in the 1980s, when monitoring of this type was out of fashion. According to a project history, "it was considered a weak science, similar to collecting stamps."
However, the scientists behind it kept it going, they modernized the procedures and now the value of the project is recognized.