The pollution of the natural environment, especially the world's oceans, with conventional plastic is of major concern. Biodegradable plastics are an emerging market bringing along potential chances and risks. The fate of these materials in the environment and their possible effects on organisms and ecosystems has rarely been studied systematically and is not well understood. For the marine environment, reliable field test methods and standards for assessing and certifying biodegradation to bridge laboratory respirometric data are lacking. In this work we present newly developed field tests to assess the performance of (biodegradable) plastics under natural marine conditions. These methods were successfully applied and validated in three coastal habitats (eulittoral, benthic and pelagic) and two climate zones (Mediterranean Sea and tropical Southeast Asia). Additionally, a stand-alone mesocosm test system which integrated all three habitats in one technical system at 400-L scale independent from running seawater is presented as a methodological bridge. Films of polyhydroxyalkanoate copolymer (PHA) and low density polyethylene (LD-PE) were used to validate the tests. While LD-PE remained intact, PHA disintegrated to a varying degree depending on the habitat and the climate zone. Together with the existing laboratory standard test methods, the field and mesocosm test systems presented in this work provide a 3tier testing scheme for the reliable assessment of the biodegradation of (biodegradable) plastic in the marine environment. This toolset of tests can be adapted to other aquatic ecosystems.

16The pollution of the natural environment, especially the world's oceans, with 17 conventional plastic is of major concern. Biodegradable plastics are an emerging 18 market bringing along potential chances and risks. The fate of these materials in the 19 environment and their possible effects on organisms and ecosystems has rarely been 20 studied systematically and is not well understood. For the marine environment, reliable 21 field test methods and standards for assessing and certifying biodegradation are 22 lacking. In this work we present newly developed field tests to assess the performance 23 of biodegradable plastics under natural marine conditions. These methods were 24 successfully applied and validated in three coastal habitats (eulittoral, benthic and polyethylene (LD-PE) were used to validate the systems. While LD-PE remained intact, 31PHA disintegrated with speed depending on the habitat and the climate zone. Together 32 with the existing laboratory standard test methods, the field and mesocosm test 33 systems presented in this work provide a 3-tier testing scheme for the reliable 34 assessment of the biodegradation of (biodegradable) plastic in the marine 35 environment. This toolset of tests can be adapted to other aquatic ecosystems. 36 37 the marine environment is increasing (e.g. [11][12][13][14][15]), however the comparison of the 70 results remains difficult. In-situ experimentation under sometimes harsh marine 71 conditions involves several risks including theft, sabotage, conflict with other activities 72 like fisheries and boating, and natural forces such as strong currents and wave action. 73Loss of samples by anthropogenic impact or natural forces [13, 15,16] could 74 substantially jeopardize the outcome of experiments. Also, most studies have only 75 tested in one habitat (e.g. [16]) or were too short-termed (e.g. [12]) to produce reliable 76 results on the full biodegradation of a certain material under marine conditions. Many 77 studies also lack the application of a positive control to assess the general microbial 78 activity under the given test conditions and the potential of the microbial community to 79 biodegrade organic materials within the experimentation time at all (e. g. [17]). 80The main goal of this study, partly conducted during the EU project Open-Bio [18, 19, 81 20], was to develop robust, reliable in-situ test systems to assess the performance of 82 biodegradable plastic materials under natural marine conditions that: (a) withstand 83 natural forces for extended times of exposure, (b) allow for testing in different marine 84 habitats without the loss of samples and (c) generate samples ideally deteriorated by 85 mere biological processes rather than physical destruction. Additionally, the aim was 86 to create a basis for an EN or ISO standard test method. 87So far, standard test methods for in-situ testing of plastic materials only exist for the 88 sea surface [21] and are now under development for the seafloor and beach scenario 89[22]. For laboratory testing se...

The performance of the biodegradable plastic materials polyhydroxybutyrate (PHB), polybutylene sebacate (PBSe) and polybutylene sebacate co-terephthalate (PBSeT), and of polyethylene (LDPE) was assessed under marine environmental conditions in a three-tier approach. Biodegradation lab tests (20°C) were complemented by mesocosm tests (20°C) with natural sand and seawater and by field tests in the warm-temperate Mediterranean Sea (12–30°C) and in tropical Southeast Asia (29°C) in three typical coastal scenarios. Plastic film samples were exposed in the eulittoral beach, the pelagic open water and the benthic seafloor and their disintegration monitored over time. We used statistical modeling to predict the half-life for each of the materials under the different environmental conditions to render the experimental results numerically comparable across all experimental conditions applied. The biodegradation performance of the materials differed by orders of magnitude depending on climate, habitat and material and revealed the impreciseness to generically term a material “marine biodegradable.” The half-life t0.5 of a film of PHB with 85 μm thickness ranged from 54 days on the seafloor in SE Asia to 1,247 days in mesocosm pelagic tests. t0.5 for PBSe (25 μm) ranged from 99 days in benthic SE Asia to 2,614 days in mesocosm benthic tests, and for PBSeT t0.5 ranged from 147 days in the mesocosm eulittoral to 797 days in Mediterranean benthic field tests. For LDPE no biodegradation could be observed. These data can now be used to estimate the persistence of plastic objects should they end up in the marine environments considered here and will help to inform the life cycle (impact) assessment of plastics in the open environment.

The performance of the biodegradable plastic materials polyhydroxyalkanoate (PHA), polybutylene sebacate (PBSe) and polybutylene sebacate co-terephthalate (PBSeT), and of polyethylene (LDPE) was assessed under marine environmental conditions in a three-tier approach. Biodegradation lab tests (20 °C) were complemented by mesocosm tests (20 °C) with natural sand and seawater and by field tests in the warm-temperate Mediterranean Sea (12 – 30 °C) and in tropical Southeast Asia (29 °C) in three typical coastal scenarios. Plastic film samples were exposed in the eulittoral beach, the pelagic open water and the benthic seafloor and their disintegration monitored over time. We used statistical modelling to predict the half-life for each of the materials under the different environmental conditions to render the experimental results numerically comparable across all experimental conditions applied. The biodegradation performance of the materials differed by orders of magnitude depending on climate, habitat and material and revealed the inaccuracy to generically term a material ‘marine biodegradable’. The half-life t0.5 of a film of PHA with 85 μm thickness ranged from 54 d on the seafloor in SE Asia to 1247 d in mesocosm pelagic tests. t0.5 for PBSe (25 μm) ranged from 99 d in benthic SE Asia to 2614 d in mesocosm benthic tests, and for PBSeT t0.5 ranged from 147 d in the mesocosm eulittoral to 797 d in Mediterranean benthic field tests. For LDPE no biodegradation could be observed. These data can now be used to estimate the persistence of plastic objects should they end up in the marine environments considered here and will help to inform the life cycle (impact) assessment of plastics in the open environment.

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