Apples to oranges? Scientists are having a hard time comparing their research findings on marine plastic

There is no standard method for analysing plastic pollution in the oceans – and no agreement on how much standardization is needed

By GRID-Arendal

March 5^th, 2021

If you look for plastic in the oceans, you will find it, and in alarming quantities. That much has become apparent during the first two days of the International Symposium on Plastics in the Arctic and Sub-Arctic Region. During day three, on Thursday, the discussion turned to the need for scientists to narrow down the ways they measure the plastic they are finding, especially microplastics.

The study of plastics in the oceans is a newish field. Plastics themselves only became widespread in the 1960s, and it wasn’t until 2004 and the publication of a paper titled “Lost at Sea: Where Is All the Plastic?” that the research wheels were set in motion.

Early on, scientists primarily used one method to study microplastics in water. The method – collecting samples, separating plastics according to their density, studying them under a microscope, analyzing them with a spectroscope, and then comparing their signatures to known values – became the gold standard.

It is still used, but nowadays scientists also employ a number of other techniques for everything from the way they capture plastic to the way they determine what it is and then describe how much they have found. Jes Vollertsen, a professor of environmental engineering at Denmark’s Aalborg University, captured some of these techniques in the following flow chart that he shared during his symposium presentation, giving a sense of how diversified this field has become.

Apples to oranges? Scientists are having a hard time comparing their research findings on marine plastic

In part, the growth in the number of analytical methods reflects the fact that the more scientists learn about plastic in the environment, the more questions they want to ask about it.

“How you analyse for microplastics depends on what you want to get out of it,” says Vollertsen. He then rolls off a long list of things those in the field would like to know: source, size, shape, composition and far more.

With increasing interest comes increasing research, and with increasing research comes a growth in the number of publications. Last year, 2,000 papers about marine microplastics were published, and that 2004 paper was cited 80,000 times. But, with so much being discussed, and so few studies discussing the matter in the same way, the result has been not just insight but also confusion.

A 2019 paper went so far, according to Vollertsen, as to declare that most of the new research findings coming out of this exponential boom in publications could not even be compared to each other.

“This is still a major problem,” he says. “We cannot compare different studies.”

A part of this can be chalked up the field’s age; it takes time to come up with standards everyone agrees on. And when there is no consensus on standards, everyone believes their own preferred standards are best, scientists lament.

“We need to find one method that is pretty simple so that you can actually use it everywhere,” says Vegard Stürzinger, a marine biologist. “Right now, everybody is just doing what they want to do.”

Hrönn Ólína Jörundsdóttir, director general at the Icelandic Food and Veterinary Authority, moderates a panel on the occurrence of plastic in the Arctic.

Do we need more standardization – or less?

Not everyone agrees that divergent analytical methods are a problem, and even those who do suggest that the quest for harmonization can go too far. If one of the mantras of the symposium so far has been that “plastic is everywhere,” another is that “there is no one-size-fits-all approach” to studying it.

This is especially true when the talk turns to studying the effect that plastics have on marine life. The northern fulmar, a species of seabird whose intake of plastic is widely studied, may be as close as scientists come to having a standard, but it is by no means the proverbial canary in the coal mine that would tell us everything we need to know, according to Jen Provencher, a research scientist with Environment and Climate Change Canada, a federal ministry.

Indeed, rather than rushing to standardize a single technique for studying plastics, it is necessary, she believes, to let scientists take the approaches that best suit their ends.

“People want to know more,” she says. “There is no silver bullet. We need to think about all of the pieces and about what we want to know about in order to select the species or compartments” that are best suited to a study.

Compartments are parts of an ecosystem, and Provencher was involved in an effort to identify which compartments of the Arctic marine environment scientists should focus on when studying plastic litter. The group started with 11. It ended up with four: water, sediments, beaches and shorelines, and seabirds.

That decision disappointed those in the field who wanted to be given a single place to look, but narrowing it down even to two, Provencher argues, would have oversimplified a situation that we still do not fully understand.

There is, in fact, an argument to be made for looking at more parts of the picture, not fewer, according to Douglas Causey, a professor at the University of Alaska Anchorage who is affiliated with the Harvard University Belfer Center for Science and International Affairs.

In the early years of studying plastics in the Arctic, for example, most research was conducted on seabirds. Nowadays there are more papers about the effects of plastics on fish. But, Causey says, just because we are studying fish more does not mean we are studying birds less.

“We know so little about the effects of plastics in the marine environment that what is happening isn’t so much a shift from seabirds to fish as it is adding other components of the food web,” he says. There is still so much to be learned.

The symposium will resume on Monday 8 March with Day Four, when the discussion will turn to efforts to monitor plastics in the marine environment and their effects on ecosystems. The focus of the final day on Tuesday will be ways forward, with conversations about how to clean up plastics and how to prevent them from entering the environment in the first place.