The amount of plastic waste floating in the northeast Pacific Ocean has increased a hundredfold in the past 40 years and is altering marine habitats, according to new research.
Scientists from the Scripps Institution of Oceanography recorded the huge rise when trawling the waters off California as part of the Scripps Environmental Accumulation of Plastic Expedition (Seaplex) in 2009.
In a study published in the journal Biology Letters, the researchers were able to compare the amount of plastic found with data stretching back to the 1970s.
‘Great Pacific Garbage Patch’
Plastic waste is an ongoing concern for the world’s oceans. All plastic waste in the ocean that does not sink is eventually broken down into small particles – termed ‘microplastics’ – by the action of sunlight and waves. Plastic pollution has been observed in oceans around the world, and is already known to affect wildlife at an individual level. Fragments of plastic can be ingested by animals, while larger pieces can also cause entanglement.
In the North Pacific Ocean, the natural circulation of the water, known as the North Pacific Gyre, tends to cause debris to accumulate in what has commonly become known as “garbage patches”. In the central North Pacific, a large patch of this plastic debris is often referred to as the “Great Pacific Garbage Patch”.
The current research follows another recent study which showed that 9% of fish collected off the Californian coast had plastic waste in their stomachs. Published in the journal Marine Ecology Progress Series, the study estimated that fish in the North Pacific Ocean could be ingesting as much as 12,000 to 24,000 tonnes of plastic a year.
Although the toxicity of plastics and the problem of ingestion by marine animals are obvious concerns, the researchers say that the broader effects of plastics on marine ecosystems also need to be examined.
They studied the association between plastic fragments and the marine insect Halobates sericeus, a relative of the common pond skater. Known as a “sea skater” or “water strider”, this species feeds on plankton and fish eggs, and in turn is prey for seabirds, fish and turtles.
The sea skater requires hard platforms on which to lay its eggs, usually using floating debris such as seabird feathers, shells, lumps of tar or even pumice rock. However, the scientists found that the numerous pieces of plastic now floating in the Pacific have provided the insect with new surfaces on which to lay its eggs, leading to a rise in its numbers.
“We thought there might be fewer Halobates if there’s more plastic – that there might be some sort of toxic effect. But, actually, we found the opposite. In the areas that had the most plastic, we found the most Halobates,” said Scripps researcher Mirian Goldstein, the lead author of the study.
“So, they’re obviously congregating around this plastic, laying their eggs on it, and hatching out from it. For Halobates, all this plastic has worked out well for them.”
The increase in the density of sea skaters could potentially have consequences for other marine species, including those that prey on the insect and its eggs. The increase in its numbers could also impact the zooplankton and fish eggs on which it feeds.
By introducing hard substrates to an area in which they are naturally rare, microplastics could therefore have broad impacts on entire ecosystems.
“The study raises an important issue, which is the addition of hard surfaces to the open ocean,” said Ms Goldstein. “In the North Pacific, for example, there’s no floating seaweed like there is in the Sargasso Sea in the North Atlantic. And we know that the animals, the plants and the microbes that live on hard surfaces are different to the ones that live floating around in the water. So, what plastic has done is add hundreds of millions of hard surfaces to the Pacific Ocean. That’s quite a profound change.”
Read more on this story at BBC News – Big rise in North Pacific plastic waste and the Scripps Institution of Oceanography press release.
Liz Shaw, ARKive Species Text Author