Microplastics and the North Sea ecosystem

Marine and coastal ecosystems are among the largest contributors to the Earth's overall productivity, i.e. the generation of biological living organisms, or biomass. These areas are currently contaminated by particles of plastic, large and small. Do these microplastics in the marine environment affect marine ecosystem productivity? This is a burning question in the minds of anyone following the growth of plastic pollution emissions to the seas and oceans of the world. A Deltares-VU Environment & Health collaboration set out to explore this question in the case of the North Sea ecosystem.
 
Previous laboratory studies had shown negative impacts of microplastics on algae or zooplankton organisms. If there is an impact on individuals in an ecosystem, populations may be impacted as well, which in turn may translate into non-negligible impacts on the productivity of the ecosystem.

Primary productivity refers to the generation of biomass by autotrophs, such as plants, which generate organic molecules out of H2O and CO2. Animal biomass is generated through secondary productivity, as biomass from primary productivity is transferred to animals which consume it to create new biomass.

In this study the potential impacts on productivity at ecosystem level were estimated based on a combination of laboratory toxicity data for both primary and secondary producers, microplastics field concentrations and a biogeochemical model for the North Sea (Delft3D-GEM). Although the model predicted that with the (uncertain) level of North Sea microplastic pollution would not affect the total primary or secondary production of the North Sea as a whole, the spatial patterns of secondary production could be altered up to ±10% in certain areas.  However, robust field data on microplastics are scarce, and large assumptions were required to include the plastic concentrations and their impacts under field conditions. As our understanding of field concentrations of microplastics and the ecotoxicological impacts on individual organisms improves, the application of ecosystem models in research and decision making will become a valuable addition to the global microplastic pollution toolbox.

The results of the study are now published in Marine Pollution Bulletin: 

Tineke A. Troost, Térence Desclaux, Heather A. Leslie, Myra D. van Der Meulen, A. Dick Vethaak. 2018. Do microplastics affect marine ecosystem productivity? Marine Pollution Bulletin 135, 17–29.

Until 18 August 2018 the publication can be downloaded for free via this link: https://authors.elsevier.com/c/1XKK8,ashq7dT

This work was supported by the European Union Seventh Framework Programme (FP7/2007–2013) under grant agreement No. 308370.

Contact: Heather Leslie heather.leslie@vu.nl or Dick Vethaak dick.vethaak@deltares.nl

Modelled impact of microplastics on secondary productivity
Modelled impact of microplastics on secondary productivity. Shown are the modelled changes in secondary productivity expressed in absolute units [g C/m2/d] (upper figure) and in relative units [-] (lower figure). Source: Troost et al. 2018

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