Product Formulation Controls the Impact of Biofouling on Consumer Plastic Photochemical Fate in the Ocean

Abstract

The photodegradation rates of floating marine plastics govern their environmental lifetimes, but the controls on this process remain poorly understood. Photodegradation of these materials has so far been studied under ideal conditions in the absence of environmental factors such as biofouling, which may slow photochemical transformation rates through light screening.To investigate this interaction, we incubated different plastics in continuous flow seawater mesocosms to follow (i) the extent of biofilm growth on the samples and (ii) decreases in light transmittance through the samples over time. We used consumer products with high relevance (e.g., shopping bags, water bottles, and packaging materials) and with different formulations, referring to primary polymers (polyethylene (PE) and polyethylene terephthalate (PET)) and inorganic additives (titanium dioxide (TiO 2 )). The behavior of consumer-relevant formulations was compared to those of pure PE and PET films, revealing that the relative effects of UV-and, to a lesser extent, visible-light screening differ based on the formulation of the product. Pure PE showed greater relative UV-transmittance decreases (Δ = −34% through the entire sample, accounting for biofilm on both sides of the plastic film) than PET (Δ = −20%) and PE products with TiO 2 (Δ = < −10%). Our results demonstrate that even with biofouling, photodegradation remains a highly relevant process for the fate of marine plastics. However, we expect photodegradation rates of plastics in the ocean to be slower than those measured in laboratory studies, due to light screening by biofilms, and the specific formulation of plastic products is a key determinant of the extent of this effect.

Plastic Formulation is an Emerging Control of Its Photochemical Fate in the Ocean

“…Our results indicate that pure, unweathered plastics are poor proxies for studying the fate and impacts (e.g., toxicity, − biogeochemical processes, ,− and biofouling) of plastics in the environment. We have known for decades that the plastics in the environment are complex mixtures that undergo weathering processes and release micro- and nanoplastics .…”

“…Like plastics, each of these materials is now known to photodegrade into thousands of unique products. 29,35,54 While it is becoming increasingly clear that plastics are not inert in the environment, more work to determine degradation rates (including variations over space and time), 7 effects of environmental factors (e.g., biofouling, 55 wavelength-dependence, 7 residence time in the photic zone, etc. ), and transformation products is needed to fully understand the fate of plastics in the environment.…”

Divergent Forms of Pyroplastic: Lessons Learned from the M/V X-Press Pearl Ship Fire

“…Water contact angle (G). The dotted line corresponds to that of reference virgin LDPE (Goodfellow). , Comparison made using a one-way ANOVA with Tukey test for multiple comparisons. For white nurdles, n = 14; for orange nurdles, n = 14; for gray nurdles, n = 13.…”

Synergy between Sunlight, Titanium Dioxide, and Microbes Enhances Cellulose Diacetate Degradation in the Ocean

“… 8 Our current findings suggest that prior sunlight exposure accelerates biodegradation, further supporting our previous conclusion that CDA is a high-utility, low-persistence material. However, we emphasize the need for additional research to assess how these findings about the photo-biodegradation of CDA may apply to different article types and characteristics (e.g., thicknesses, morphologies, formulations) under varying environmental conditions (e.g., temperature, nutrients, irradiance levels, salinity, sunlight screening by biofilms 58 ).…”