Parts of microplastics can also be used as building blocks for cell membranes of aquatic animals in addition to the often-reported toxic effects. Even the carbon of omega-3 fatty acids, which are so important for humans, can originate from microplastics. These are the key results of investigations an international group of scientists conducted under participation of the research group LIPTOX of Danube University Krems at the WasserCluster Lunz. Nature Scientific Reports published the results.
Every year, more than 440 million tons of plastic are produced worldwide, with a large part ditched into the oceans, but also into lakes, rivers and creeks. Researchers from Finland alongside with the research group LIPTOX of Danube University Krems at the WasserCluster Lunz discovered and recently published in a new study that some parts of microplastics can be used as building blocks for cell membranes of aquatic animals.
In order to give proof of this the researchers followed an innovative way. They used 13C-polyethylene marked with stable carbon isotopes, in other words microplastics, and let this only decompose by bacteria naturally occurring in lakes. The bacteria took up parts of the microplastics and were consequently taken up by so-called mixotrophic algae - algae that can also absorb bacteria as food.
Faster algae growth
These algae synthesized essential omega-3 fatty acids from the bacteria containing 13C polyethylene, which are important building blocks of cell membranes. These algae grew even faster by absorbing bacteria than in their autotrophic mode (i.e. by mere photosynthesis). Finally, these algae were fed to water fleas (Daphnia magna) and then their fatty acids of the cell membranes were studied. Together with the LIPTOX research group led by Doz. Dr. Martin Kainz, at the WasserCluster Lunz, an inter-university Institute for Aquatic Ecosystem Research, the researchers were able to prove that carbon from microplastics reaches the aquatic animals via bacteria and mixotrophic algae and contributes to the formation of cell membranes. For this, the scientist used a state-of-the-art isotope mass spectrometer coupled to a gas chromatograph.
These research results show how microplastics can be used as part of cell building blocks in addition to the often reported toxic effects. Another result: even the carbon of the omega-3 fatty acids, which are so important for humans, can originate from microplastics.
S. J. Taipale, E. Peltomaa, J. V. K. Kukkonen, M. J. Kainz, P. Kautonen & M. Tiirola, Tracing the fate of microplastic carbon in the aquatic food web by compound specific isotope analysis, Nature Scientific Reports 2019, 9:19894