The increase in ocean plastic pollution documented over six decades

 

By Siobhán Dunphy

Plastic use became widespread in the 1950s and since then plastic pollution of land, seas, and even the atmosphere has ballooned into a major cause for global concern. And the amount of plastic polluting the oceans has risen dramatically, according to a new study published on 16 April in Nature Communications, which documents an incredibly unique dataset (1) — to come up with their conclusions, the scientists analysed 60 years worth of logbooks from a plankton-tracking study.

Plastics degrade slowly and pose serious potential health risks to humans and animals. Moreover, health impacts on marine species are associated with entanglement, ingestion, and toxicity. However, long-term environmental datasets on plastic debris and its adverse effects are limited, particularly in the open ocean.

TRACKING PLANKTON AND PLASTIC

The handwritten logs examined by the researchers from The Marine Biological Association in Plymouth, UK were written about samples from the Continuous Plankton Recorder, a large instrument designed to capture plankton samples over huge areas of the ocean over the 60-year period.

The device traverses around 6.5 million nautical miles over the six decades and since 1931, has been keeping a record of pelagic plankton ― diverse organisms that provide a source of food for many marine species and indicate water quality.

The time series spans from 1957 to 2016 and the data were retrospectively analysed to reveal a significant increase in plastic pollution between 1960–70 to 1980–1990. These are “some of the earliest records of plastic entanglement” and “the first to confirm a significant increase in open ocean plastics in recent decades,” the authors write.

The logs first document a piece of twine, found in the 1950s, followed by a plastic carrier bag, discovered in 1965. Then increasing reports of plastic objects and even some incidences of marine creatures, such as turtles and seabirds, snagged in plastic.

According to the authors, the trackers have become entangled in large plastic objects, such as bags and fishing lines, around three times more often since the year 2000, compared to the preceding decades. Interestingly, they did not note any significant trend between the 1980s and the 1990s, however, the data does confirm “a significant increase in open ocean plastics since the 1990s”.

The findings are far from surprising, but this is the first study to provide evidence across such a long time-scale. In the 2000s, entanglements recorded in roughly 3% of tows, compared to 1 per cent in the 50s, 60s and 70s and reaching 2% by the 90s. Whereas, there was no significant change in the number of entanglements with seaweed and fish over the same period.

A total of 208 entanglements were recorded over the 60-year period fishing gear was responsible for more than half of these but encounters with large plastic items have also become increasingly more common. Furthermore, there is no data on microplastics, which are increasingly recognised as a serious global problem. Nonetheless, the evidence highlights that fisheries do, indeed, play a large role in plastic pollution.

THE FINDINGS ARE YET ANOTHER CALL TO ACTION

There are very few continuous historical records such as these that can confirm the increasing and detrimental presence of plastics in the ocean. The study confirms the expected significant increase in plastics in the open ocean since the 1990s, which matches an exponential increase in total plastic production worldwide, the authors conclude. They also highlight the importance of actions to reduce plastic pollution, particularly in the fishing industry.

(1) Ostle, C. et al. The rise in ocean plastics evidenced from a 60-year time series. Nature Communications (2019). DOI: 10.1038/s41467-019-09506-1

 
Rachel Chea