Whales in the vicinity of the city of Auckland, New Zealand consume large amounts of microplastics every day. A team of international researchers reached this conclusion after carefully examining whale poop. The team included Thijs Bosker, Associate Professor in Environmental Sciences at Leiden University College The Hague (LUC) and the Institute of Environmental Sciences (CML), and Laura Zantis, a PhD researcher from Leiden University,
To Bosker, it was no surprise that microplastics were present: ‘We know they are everywhere.’ It was the amount of plastic whales consume that surprised him: an estimated three million microplastics per day. This is the first time this kind of study – researching scat instead of just taking water samples to determine the scale of pollution – has been done in whales. ‘Essentially, whales are continuously sampling both their environment and their prey when they feed,’ says Laura Zantis. ‘By researching their scat, we wanted to understand how many microplastics they consume each day and whether those microplastics were in the whales’ food or from water swallowed during feeding.’
Underestimation of amount
The research team discovered via the scat that the whales in the Harauki Gulf near Auckland were mainly eating small zooplankton such as krill. By calculating how much prey whales consumed per mouthful of krill, the researchers estimate that the whales consume about 25,000 microplastics every time they catch prey. Most of those microplastics come from prey, with only about 1 in 1000 coming from the water.
The microplastics originate from a large variety of man-made products, such as cigarette filters, clothing and plastic bottles. Bosker believes that the findings are probably an underestimation of the amount of plastic the whales consume because the even smaller nanoplastics were not part of the research.
Next step in research
Bosker and Zantis expect their findings to help with further research. Bosker: ‘Of the three important questions – is it in the environment, is there uptake and are there negative effects? – we have now answered two. The next question we want to answer is: do these microplastics have negative effects on the organism? Three million sounds like a lot, but we need to determine how harmful it is.’
Zantis is continuing her microplastics research in Leiden as a PhD candidate at the CML, albeit in a different area. ‘I will be looking at the effects of microplastics on plants.’ Bosker adds: ‘The questions remain the same, whether you work with whales or plants. Although it’s a lot of fun to work with whales.’