EGU General Assembly 2023
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

The submarine Congo Canyon as a conduit for microplastics to the deep sea

Florian Pohl1, Lars Hildebrandt2, Joey O’Dell3, Peter Talling4, Megan Baker5, Fadi El Gareb2,6, Jacopo La Nasa7, Francesca De Falco1, Marco Mattonai7, Sean Ruffell8, Joris Eggenhuisen3, Francesca Modugno7, Daniel Proefrock2, Ed Pope4, Ricardo Silva Jacinto9, Maarten Heijnen10,11, Sophie Hage12,13, Stephen Simmons14, Martin Hasenhündl15, and Catharina Heerema8
Florian Pohl et al.
  • 1University of Plymouth, United Kingdom of Great Britain – England, Scotland, Wales (
  • 2Department for Inorganic Environmental Chemistry, Helmholtz-Zentrum Hereon, Germany
  • 3Faculty of Geosciences, Utrecht University, The Netherlands
  • 4Departments of Geography and Earth Science, Durham University, United Kingdom
  • 5Department of Geography, Durham University, United Kingdom
  • 6Department of Geoscience, Universität Hamburg, Institute of Geology, Germany
  • 7Department of Chemistry and Industrial Chemistry, University of Pisa, Italy
  • 8Department of Earth Sciences, Durham University, United Kingdom
  • 9Marine Geosciences Unit, IFREMER Centre de Brest, France
  • 10National Oceanography Centre Southampton, United Kingdom
  • 11School of Ocean and Earth Sciences, University of Southampton, United Kingdom
  • 12University of Brest, CNRS, IFREMER, Geo-Ocean, France
  • 13Department of Geosciences, University of Calgary, Canada
  • 14Energy and Environment Institute, University of Hull, United Kingdom
  • 15Institute of Hydraulic Engineering and Water Resources Management, TU Wien, Austria

The increasing plastic pollution of the world’s oceans represents a serious threat to marine ecosystems and has become a well-known topic garnering growing public attention. The global input of plastic waste into the oceans is estimated to be approximately 10 million tons per year and predicted to rise by one order of magnitude by 2025. More than 90% of the plastic that enters the oceans is thought to end up on the seafloor, and seafloor sediment samples show that plastics are concentrated in confined morphologies and sedimentary environments such as submarine canyons. These canyons are occasionally flushed by powerful gravity-driven sediment flows called turbidity currents, which transport vast volumes of sediment to the deep sea and deposit sediment in deep-sea fans. As such, turbidity currents may also transport plastics present in the canyon and bury plastics in deep-sea fans. These fans may therefore act as sinks for seafloor plastics. Here we present a comprehensive dataset showing the spatial distribution of microplastics in seafloor sediments from the Congo Canyon, offshore West Africa. Multicores taken from 16 locations along the canyon, sampled different sedimentary sub-environments including the canyon thalweg, canyon terraces, and distal lobe. Microplastics were extracted from the sediments by density separation and the polymer type, size, and shape of all individual microplastic particles were analysed using laser-direct infrared-spectroscopy (LDIR). Microplastic number concentrations in the sediments of the distal lobe are significantly higher than in the canyon, indicating that the Congo Canyon system is a highly efficient conduit for microplastic transport to the deep sea. Moreover, microplastic concentrations of >20,000 particles per kg of dry sediment were recorded in the lobe, which represent some of the highest ever recorded microplastic number concentrations in seafloor sediments. This shows that deep-sea fans can serve as hotspots and potential terminal sinks for seafloor microplastics.

How to cite: Pohl, F., Hildebrandt, L., O’Dell, J., Talling, P., Baker, M., El Gareb, F., La Nasa, J., De Falco, F., Mattonai, M., Ruffell, S., Eggenhuisen, J., Modugno, F., Proefrock, D., Pope, E., Silva Jacinto, R., Heijnen, M., Hage, S., Simmons, S., Hasenhündl, M., and Heerema, C.: The submarine Congo Canyon as a conduit for microplastics to the deep sea, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-12344,, 2023.