Macrofouling communities and the degradation of plastic bags in the sea: an insitu experiment.

Nora-Charlotte Pauli,Christian Lott,Miriam Weber,Jana S. Petermann

doi:10.1098/rsos.170549

Abstract

The increasing amount of plastic littered into the sea may provide a new substratum for benthic organisms. These marine fouling communities on plastic have not received much scientific attention. We present, to our knowledge, the first comprehensive analysis of their macroscopic community composition, their primary production and the polymer degradation comparing conventional polyethylene (PE) and a biodegradable starch-based plastic blend in coastal benthic and pelagic habitats in the Mediterranean Sea. The biomass of the fouling layer increased significantly over time and all samples became heavy enough to sink to the seafloor. The fouling communities, consisting of 21 families, were distinct between habitats, but not between polymer types. Positive primary production was measured in the pelagic, but not in the benthic habitat, suggesting that large accumulations of floating plastic could pose a source of oxygen for local ecosystems, as well as a carbon sink. Contrary to PE, the biodegradable plastic showed a significant loss of tensile strength and disintegrated over time in both habitats. These results indicate that in the marine environment, biodegradable polymers may disintegrate at higher rates than conventional polymers. This should be considered for the development of new materials, environmental risk assessment and waste management strategies.

Highlights

The increasing amount of plastic littered into the sea may provide a new substratum for benthic organisms
We investigated the biomass of the fouling layer, the composition of the macrofouling communities, their biodiversity, their oxygen production/consumption, as well as the disintegration and the tensile properties of MaterBi® and PE carrier bags
We aimed to test the following hypotheses: (i) the biomass of the fouling layer increases with time, (ii) the macrofouling communities and their structure are specific to the polymer type and to the habitat to which the polymer is exposed, (iii) the net primary production of the fouling community is positive in both habitats and higher in the pelagic habitat compared to the benthic habitat, and (iv) the biodegradable polymer disintegrates and loses tensile properties at similar rates in both habitats, while the polyethylene polymer does not show signs of disintegration and loss of tensile properties in either of the two habitats

Summary

Introduction

The increasing amount of plastic littered into the sea may provide a new substratum for benthic organisms. These marine fouling communities on plastic have not received much scientific attention. To our knowledge, the first comprehensive analysis of their macroscopic community composition, their primary production and the polymer degradation comparing conventional polyethylene (PE) and a biodegradable starch-based plastic blend in coastal benthic and pelagic habitats in the Mediterranean Sea. The biomass of the fouling layer increased significantly over time and all samples became heavy enough to sink to the seafloor. Contrary to PE, the biodegradable plastic showed a significant loss of tensile strength and disintegrated over time in both habitats These results indicate that in the marine environment, biodegradable polymers may disintegrate at higher rates than conventional polymers. MaterBi® was tested in and on marine coastal sediments in laboratory experiments where it was biodegraded by 90% after less than a year [10]

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Conclusion