Aquatic ecosystems suffer disproportionately from plastic pollution given that they integrate material from terrestrial watersheds. Most studies on microbial colonisation and degradation of plastics have focused on marine environments, leaving a knowledge gap for freshwaters. Our study explores the possible degradation and the role of bacterial community composition of plastics in Lake Geneva. We exposed polyethylene terephthalate (PET) and low-density polyethylene (LDPE) for 45 weeks to environmental lake gradients that change with depth and season. The substrates were suspended at 2 and 30 m depth, resulting in strikingly different environmental conditions for biofilm development, including light (PAR), temperature, and nutrient availability. We monitored the bacterial colonisation using 16S rRNA sequencing and assessed the abundance of the alkane hydrolase gene (alkB) to evaluate the potential ability of the biofilm to degrade PET and LDPE. Additionally, we analysed plastic surface modifications through spectroscopy, contact angle measurements and microscopy. We found that the PET surface showed no degradation after 45 weeks in the lake, at either depth. The LDPE surface at 2 m exhibited a decrease in hydrophobicity, but no evidence of oxidation or degradation was found. In contrast, the LDPE surface at 30 m displayed oxidation, a decrease in hydrophobicity, and porous cavities. In addition, we observed an increase in the alkane alkB gene abundance in the biofilm, with the development of plastic-degrading taxa in the community. Our results underline the complexity of plastic degradation in aquatic ecosystems; not only does the type of plastic have an effect, so do the spatio-temporal variable environmental lake conditions and the biofilm community. The multifactorial nature of these processes complicates predictions on the fate of plastics in the environment.

• Klíčová slova
• Biofilm, Degradation, Freshwater, Plastics, Weathering,
• MeSH
• Bacteria metabolismus   MeSH
• biodegradace MeSH
• biofilmy MeSH
• chemické látky znečišťující vodu * metabolismus   analýza   MeSH
• jezera * mikrobiologie   chemie   MeSH
• mikrobiota MeSH
• monitorování životního prostředí MeSH
• plastické hmoty * metabolismus   analýza   MeSH
• polyethylentereftaláty MeSH
• roční období MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• chemické látky znečišťující vodu * MeSH
• plastické hmoty * MeSH
• polyethylentereftaláty MeSH

Currently, the environmental problems associated with plastic production and waste, such as the consequences of worldwide pollution of natural waters with microplastics, have led to the seeking of alternative materials that can at least partially replace conventional petroleum-based plastics. Substitute materials include bioplastics and similar plant-based materials or their composites. However, their fate when disposed of in unintended environments (e.g., water bodies) remains largely unknown, while such information is highly desirable prior to massive expansion of exploiting such materials. This study aims to contribute filling this knowledge gap. Specifically, 19 different types of bioplastic and similar plant-based material debris (corresponding to the size of microplastics) were kept in long-term contact with water to mimic their behaviour as water pollutants, and the leachates were continuously analysed. Eighteen of the 19 investigated materials released significant amounts of dissolved organic carbon-up to 34.0 mg per g of debris after 12 weeks of leaching. Each leachate also contained one or more of the following elements: Al, B, Ba, Ca, Fe, K, Mg, Mn, N, Na, P, Si, Ti, and Zn. Non-targeted analysis aimed at providing more specific insight into the leachate composition tentatively revealed 91 individual chemicals, mostly fatty acids and other carboxylic acids, phthalates, terephthalates, adipates, phenols, amides, alcohols, or organophosphates. Based on the compound characteristics, they might be additives, non-intentionally added substances, as well as their degradation products. In general, the current results imply that bioplastics and similar plant-based materials should be considered complex materials that undergo industrial processing and comprise additives rather than harmless natural matter. Additionally, various compounds can release from the bioplastic and similar plant-based material debris when deposited in water. It might have consequences on the fluxes of carbon, metals and specific organic contaminants, and it resembles some properties of conventional petroleum-based microplastics.

• Klíčová slova
• Bio-based materials, Biodegradable materials, Dissolved organic carbon (DOC), Microplastics, Non-targeted analysis, Water quality,
• MeSH
• chemické látky znečišťující vodu * analýza   MeSH
• kovy * analýza   MeSH
• mikroplasty analýza   MeSH
• monitorování životního prostředí * metody   MeSH
• plastické hmoty analýza   MeSH
• uhlík * analýza   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• chemické látky znečišťující vodu * MeSH
• kovy * MeSH
• mikroplasty MeSH
• plastické hmoty MeSH
• uhlík * MeSH