The accumulation of plastic pollution in marine sediments are projected to surpass organic carbon loads in some places in the near future. Therefore, it is important to understand the effects on these blue carbon zones, especially amid the climate crisis. We used a carbon consumption assay to gauge the effects of increased plastic pollution to the seafloor. Assay plates were filled with carbon-based media with and without polyester microfibers. To incorporate habitat heterogeneity, plates were deployed at 10 plots, each reaching 15 cm in depth, across intertidal flats of the Waitemata Harbour of Auckland, New Zealand. Results showed that media consumption rates change spatially and are largely driven by organic matter content, mud content, or mean grain size. This highlights the dependency of carbon degradation on the ambient sedimentary environment. Importantly, sedimentary environmental drivers were different for media with and without microplastic. Our results indicate that microplastic polyester fibers break ecosystem relationships and alter carbon cycling dynamics. Most importantly, our results illustrate the essential role that habitat heterogeneity plays in seafloor carbon consumption and the complexity of real-world microplastic-ecosystem impacts. Our multidisciplinary approach adds context to ecosystem-level effects of plastic pollution on seafloor carbon consumption rates.

Primary Presenter: Samantha Ladewig, University of Auckland (samanthamladewig@gmail.com)

Authors:

Samantha Ladewig, University of Auckland  (slad852@aucklanduni.ac.nz)

Thomas Bianchi, University of Florida  (tbianchi@ufl.edu)

Giovanni Coco, University of Auckland  (g.coco@auckland.ac.nz)

Eliana Ferretti, University of Auckland  (efer020@aucklanduni.ac.nz)

Rebecca Gladstone-Gallagher, University of Auckland  (rebecca.gladstone-gallagher@auckland.ac.nz)

Jenny Hillman, University of Auckland  (j.hillman@auckland.ac.nz)

Julie Hope, The University of St. Andrews  (jah23@st-andrews.ac.uk)

Candida Savage, University of Otago  (candida.savage@otago.ac.nz)

Stefano Schenone, University of Auckland  (s.schenone@auckland.ac.nz)

Simon Thrush, University of Auckland  (simon.thrush@auckland.ac.nz)