Microbial colonization and degradation of polyethylene and biodegradable plastic bags in temperate fine-grained organic-rich marine sediments Alice Nauendorf a , Stefan Krause a , Nikolaus K. Bigalke a , Elena V. Gorb b , Stanislav N. Gorb b , Matthias Haeckel a , Martin Wahl c , Tina Treude a, ⁎ ,1 a Department of Marine Biogeochemistry, Helmholtz Centre for Ocean Research Kiel (GEOMAR), 24148 Kiel, Germany b Department of Functional Morphology and Biomechanics, Zoological Institute, Kiel University, 24098 Kiel, Germany c Department of Benthic Ecology, Helmholtz Centre for Ocean Research Kiel (GEOMAR), 24148 Kiel, Germany abstract article info Article history: Received 7 October 2015 Received in revised form 11 December 2015 Accepted 17 December 2015 Available online xxxx To date, the longevity of plastic litter at the sea floor is poorly constrained. The present study compares coloniza- tion and biodegradation of plastic bags by aerobic and anaerobic benthic microbes in temperate fine-grained organic-rich marine sediments. Samples of polyethylene and biodegradable plastic carrier bags were incubated in natural oxic and anoxic sediments from Eckernförde Bay (Western Baltic Sea) for 98 days. Analyses included (1) microbial colonization rates on the bags, (2) examination of the surface structure, wettability, and chemistry, and (3) mass loss of the samples during incubation. On average, biodegradable plastic bags were colonized five times higher by aerobic and eight times higher by anaerobic microbes than polyethylene bags. Both types of bags showed no sign of biodegradation during this study. Therefore, marine sediment in temperate coastal zones may represent a long-term sink for plastic litter and also supposedly compostable material. © 2015 Published by Elsevier Ltd. Keywords: Biodegradation Biofilm Microorganisms Carrier bag Compostable Eckernförde Bay 1. Introduction The production of plastic material has constantly increased over the past 50 years (PlasticsEurope, 2013) and contributes to the resulting pollution of marine environments (Derraik, 2002). Polyethylene (PE) is a major component of plastic waste found in oceans (Morét-Ferguson et al., 2010; Zettler et al., 2013), on shorelines, at the ocean surface, and on the sea floor, mostly in the form of carrier bags (Barnes et al., 2009). Marine plastic pollution may harm marine organisms via ingestion or entanglement, and may favor the dispersal of invasive species (Gregory, 2009). Additionally, the release of hazardous chemicals, including additives (components of plastic) and the accumulation of hy- drophobic toxins (adsorbed onto plastic from surrounding sea water) were reported (Teuten et al., 2009). Due to the longevity of plastic in the environment and the ensuing long-term threat to organisms, alternatives to these synthetic polymers were developed and tested (O'Brine and Thompson, 2010). Different types of degradable plastics are commercially available, such as natural plastics produced by microorganisms, or plastics with polymer blends, such as starch and photo-biodegradable plastics (Shah et al., 2008). To date, studies focus- ing on different types of degradable plastics, marine environments and locations have been conducted by Accinelli et al. (2012); Andrady et al. (1993), Rutkowska et al. (2002) and Tosin et al. (2012). The mentioned studies obtained conflicting results and it remains unclear whether degradable plastics are less harmful. Microbes are ubiquitously abundant in the marine environment, ca- pable of decomposing complex organic matter. Hence, the question arises whether microbial degradation of plastic litter is possible and whether it has the capacity to counteract the gradual accumulation of plastics in marine environments. So far, most studies on the microbio- logical colonization and degradation of plastic are restricted to the upper ocean layer. Zettler et al. (2013) described a diverse microbial community growing on plastic material from North Atlantic surface water, which differed from the bacterial composition of the surrounding water. Pits in the plastic surface of the same size and shape as that of bacteria were interpreted as possible features of biodegradation. In another study, polyethylene (PE) incubated for 20 months in 2 m water depth in the Baltic Sea showed no biodegradation (Rutkowska et al., 2002). The initial positive buoyancy and the hydrophobicity of PE may be altered by UV–radiation, oxidation, high temperatures (Andrady, 2011, Shah et al., 2008), and biofilm formation (Muthukumar et al., 2011). After approximately three weeks of floating at the ocean surface, Marine Pollution Bulletin xxx (2015) xxx–xxx ⁎ Corresponding author. E-mail addresses: anauendorf@geomar.de (A. Nauendorf), ttreude@g.ucla.edu (T. Treude). 1 Present address: Department of Earth, Planetary, and Space Sciences & Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles, CA 90095, USA. MPB-07376; No of Pages 11 http://dx.doi.org/10.1016/j.marpolbul.2015.12.024 0025-326X/© 2015 Published by Elsevier Ltd. Contents lists available at ScienceDirect Marine Pollution Bulletin journal homepage: www.elsevier.com/locate/marpolbul Please cite this article as: Nauendorf, A., et al., Microbial colonization and degradation of polyethylene and biodegradable plastic bags in temperate fine-grained organic-rich marine sediments, Marine Pollution Bulletin (2015), http://dx.doi.org/10.1016/j.marpolbul.2015.12.024