Beaches covered in disposable water bottles and flip-flops. A dead whale with more than 20 kg of plastic in its stomach. A sea horse swimming around with its tail twisted around a cotton swab. Plastic waste in the sea is easy to see, which makes it an environmental issue that is easy to understand.
Through his thirty years as a marine biologist, Torkel Gissel Nielsen, Professor of biological oceanography at DTU Aqua, has not previously seen such a large, widespread, and long-standing agreement—across political beliefs and geographic borders—on a sea matter.
“But does that make plastic our biggest environmental issue? And if it does, where is the evidence?” asks the Professor and elaborates:
“The debate is guided by emotions rather than facts, due to a lack of basic knowledge about plastics in the marine environment. How much plastic is there? Where is it, and what happens to it? And how does it affect life in the sea—or humans? We have no answers to these fundamental questions yet.”
Acquiring more knowledge
Professor Torkel Gissel Nielsen has been concerned with plastics in the sea for several years and has, among other things, been involved in investigating the distribution of plastics on the route between Denmark and the Sargasso Sea south of Bermuda, as well as taking part in analyses of fish and water samples from the Baltic Sea to determine the levels of microplastics in both. None of his studies have led to alarming results.
He is currently working on several studies with MarinePlastic—a new research centre which is a collaboration between DTU, Aalborg University, Aarhus University, Roskilde University, and the National Museum of Denmark—and the goal is exactly to gain more knowledge about plastics in the marine environment.
However, Torkel Gissel Nielsen and his colleagues can already now see that certain assertions are completely untrue, while others are merely undocumented.
Plastic islands in the sea
“There are no islands of plastic in the oceans. It’s true that there are a number of larger gyres where sea currents increase the concentration of both large and small pieces of plastic. On DTU Aqua’s expedition to the Sargasso Sea south of Bermuda in 2014, we sailed through the North Atlantic Gyre. We didn’t see a plastic island. We only came upon a larger piece of plastic every two minutes or so. We took water samples and examined them for microplastics, and we found between 0.1 and 0.5 microplastics particles per litre of seawater. That is not very much. However, it’s still a sign that humans have managed to spread plastic to the environment. Other international studies have found plastics in the world’s deepest ocean trench, the Mariana Trench, and as far away as in the penguin colonies on Antarctica. That in itself is worrying. So it shouldn’t be necessary to use false information about plastic islands to make people aware of the problem.”
Whales eat plastic and die
“It’s true that dead whales have been found with plastic in their stomachs. But that doesn’t mean that plastics are the reason they died. We don’t know why the whales are dead. It may be that they were sick or old. There shouldn’t be plastic in their stomachs, of course, but we can’t just make the conclusion that they died from it. On the other hand, it is well-documented that other larger animals such as sea turtles and seabirds can suffer from eating plastics. We don’t know whether the concentrations of microplastics we find in the sea today affect smaller animals such as plankton and small fish. English researchers have recently shown that microplastics can have a negative effect on the growth and reproductive capacity of marine animals. But it’s important to note that their experiments were made with a microplastics concentration that’s between 10,000 and a million times higher than the concentrations we find in the sea today.”
Fish become inedible
“Plastics have been found in fish stomachs and intestines. No matter where you fish–whether it’s in Kattegat or somewhere near New Zealand—you will find a small piece of plastic in the intestinal system of ten to 50 per cent of those fish. But we don’t know whether that has any influence on the fish as food. We have shown that microplastics can pass through animals and be excreted again. The same thing happens to humans, because plastic doesn’t pass through the intestinal wall. But we don’t know whether this is the case for nanoplastics, nor do we know whether the chemicals that plastics can carry with them pose a problem. In other words, we don’t know the health-related consequences of plastics.”