As a microbiologist, Gerdts is not only interested in the plastic particles themselves, but also the microorganisms that settle on plastic surfaces. This is a perfectly natural process, since bacteria and single-celled organisms in the sea settle on practically every surface they can find – stones, ships’ hulls, or snail shells.
Gerdts and his colleagues have found various groups of microorganisms on the microplastic. Their most troubling discovery is that they also include pathogens – like the bacteria Vibrio parahaemolyticus, which can cause gastroenteritis, diarrhoea and vomiting. “Who knows,” he says, “In the future, the masses of microplastic accumulating in the ocean might promote the spread of diseases.”
The long-term consequences of the growing amount of microplastic in our ocean also interest Gerdts’ colleague Lars Gutow, a biologist whose work explores e.g. the effects of marine organisms consuming plastic particles when they feed. Gutow has found that different groups of organisms react differently to the particles: when it comes to isopods, the particles pass through their digestive tract and are simply excreted.
Yet the research of his AWI colleague Angela Köhler show that, in bivalves, the particles can spread from the digestive tract to the tissues and cells, where they can cause inflammations. “However, we should bear in mind that the microparticle concentrations used in the laboratory experiments were extremely high, so we can’t yet say for sure if the same inflammations would occur under natural conditions,” Gerdts adds.