EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

A stable isotope assay for determining microbial degradation rates of plastics in the marine environment

Maaike Goudriaan1, Victor Hernando Morales1,2, Ronald van Bommel1, Marcel van der Meer1, Rachel Rachel Ndhlovu1, Johan van Heerwaarden1, Kai-Uwe Hinrichs3, and Helge Niemann1,4,5
Maaike Goudriaan et al.
  • 1NIOZ Royal Netherlands Institute for Sea Research, Department of Marine Microbiology & Biogeochemistry, 't Horntje (Texel) The Netherlands
  • 2University of Vigo, Biological Oceanography Group,Vigo (Pontevedra) Spain
  • 3University of Bremen, MARUM, Bremen, Germany
  • 4University of Utrecht, Faculty of Geosciences Department of Earth Sciences, Utrecht, The Netherlands
  • 5at University of Tromsø CAGE - Centre for Arctic Gas Hydrate, Environment and Climate, Tromsø, Norway

The popularity of plastic as a cheap and easy to use, moldable material has been growing exponentially, leading to a likewise increase in plastic waste. As a result, plastic pollution has been surging in the marine realm, and the effects and fates of these modern, man-made compounds in our oceans are unresolved. Pathways of plastic degradation (physicochemical and biological) in the marine environment are not well constrained; yet, microbial plastic degradation is a potential plastic sink in the ocean. However, there is a lack of methods to determine this process, particular if the overall turnover is in the sub-percent range.  We developed a novel method based on incubations with isotopically labelled polymers for investigating microbial plastic degradation in marine environments. We tested our method with a Rhodococcus Ruber strain (C-208), a known plastic degrader, as a model organism. In our experiments we used granular polyethylene (PE) that was almost completely labelled with the stable isotope 13C (99%) as a sole carbon source. We monitored CO2 concentration and stable carbon isotope ratios over time in the headspace during 35-day incubations at atmospheric oxygen concentrations and found an excess production of 13C-CO2. This result provides direct evidence for the microbially mediated mineralization of carbon that was ultimately derived from the polymer. After terminating the incubation, we measured the dissolved inorganic carbon (DIC), and pH, allowing us to determine the total excess production of 13C-CO2 and DIC, and thus the rate of plastic degradation. Of the 2000 μg PE added, ~0.1% was degraded over a time course of 35 days at a rate of ~1.5 μg month-1, providing a first characterization of the mineralization kinetics of PE by R. Ruber. The results show that isotopically labelled polymers can be used to determine plastic degradation rates. The method shows promise for being more accurate than the classic gravimetrical methods.

How to cite: Goudriaan, M., Hernando Morales, V., van Bommel, R., van der Meer, M., Rachel Ndhlovu, R., van Heerwaarden, J., Hinrichs, K.-U., and Niemann, H.: A stable isotope assay for determining microbial degradation rates of plastics in the marine environment, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-15253,, 2020


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