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Journal Articles

A New approach to extracting biofilm from environmental plastics using ultrasound-assisted syringe treatment for isotopic analyses

Battulga, B.; Atarashi-Andoh, Mariko; Nakanishi, Takahiro; Koarashi, Jun

Science of the Total Environment, 849, p.157758_1 - 157758_11, 2022/11

 Times Cited Count:1 Percentile:45.99(Environmental Sciences)

Characterizing plastic-associated biofilms is key to the better understanding of organic material and mineral cycling in the "Plastisphere"-the thin layer of microbial life on plastics. In this study, we propose a new method to extract biofilms from environmental plastics, in order to evaluate the properties of biofilm-derived organic matter through stable carbon ($$delta$$$$^{13}$$C) and nitrogen ($$delta$$$$^{15}$$N) isotope signatures and their interactions with radionuclides especially radiocesium ($$^{137}$$Cs). After ultrasound-assisted separation from the plastics, biofilm samples were successfully collected via a sequence of syringe treatments. Biofilm-derived organic matter samples (14.5-65.4 mg) from four river mouths in Japan showed $$^{137}$$Cs activity concentrations of $$<$$75 to 820 Bq kg$$^{-1}$$ biofilm (dw), providing evidence that environmental plastics, mediated by developed biofilms, serve as a carrier for $$^{137}$$Cs in the coastal environment. Significant differences in the ($$delta$$$$^{13}$$C and $$delta$$$$^{15}$$N signatures were also obtained for the biofilms, indicating the different sources, pathways, and development processes of biofilms on plastics.

Oral presentation

A New approach to extracting biofilm from environmental plastics using ultrasound-assisted syringe treatment for isotopic analyses

Battulga, B.; Atarashi-Andoh, Mariko; Koarashi, Jun

no journal, , 

Plastic debris has been recognized as one of the carriers of hazardous substances in the aquatic ecosystem due to its ubiquitous distribution and potential interaction with pollutants through developed biofilms. In this study, we aimed to extract biofilms from the environmental plastics using a newly developed extraction method and to determine the concentration of radiocesium ($$^{137}$$Cs) and stable isotope ratios ($$delta$$$$^{13}$$C and $$delta$$$$^{15}$$N) in the extracted biofilm samples. Visible plastics were collected from the mouths of coastal rivers in Ibaraki prefecture, Japan, and applied to the extraction procedures. After plastic and biofilm separation with ultrasonication, biofilm samples were collected by the two ways: freeze-drying (15.5-44.4 mg); and freeze-drying after syringe treatment (14.5-65.4 mg). The XRD diffractograms of biofilm samples confirmed that biofilms obtained by freeze-drying only were still heterogeneous and the agglomerations of organic substances, mineral particles, and small microplastics (MPs, $$<$$ 1 mm). The results also demonstrated that biofilm extraction was achieved by syringe treatment separating the mineral and small MPs particles, resulting in homogenous biofilms from the surface of plastics. Preliminarily results of $$^{137}$$Cs activity concentrations in heterogenous (ranging from 0.22 to 0.54 Bq g$$^{-1}$$) and homogenous (0.82$$pm$$0.04 Bq g$$^{-1}$$) biofilm samples revealed that MPs serve as a carrier for $$^{137}$$Cs in the coastal river environment mediated by developed biofilms.

Oral presentation

Characterizations of formed biofilms and microbial communities on microplastics in coastal rivers of Japan

Battulga, B.; Nakayama, Masataka; Atarashi-Andoh, Mariko; Koarashi, Jun

no journal, , 

Plastic debris in the aquatic environment has become a growing concern due to their long-term ecological consequences. The current study is focused on microbial community composition on microplastics (MPs; sizes $$<$$5 mm) and characteristics of MP-associated biofilms in coastal river environments of Japan in order to understand the impact of MP-associated biofilms on aquatic organic matter cycling. The aims of the current study are i) extraction and characterization of microbial biofilms on MPs and ii) identification of diversity and composition of microbial communities on MP surfaces and in surrounding surface waters and sediments. The samples were collected from two coastal rivers during 2021-2022 on a seasonal basis. In this study, we proposed a new method to extract biofilms from MPs using ultrasound-assisted syringe treatment for isotopic analysis. Morphotypes of MPs and associated specific microbial taxa as well as seasonal differences were also observed.

Oral presentation

Microbial life on plastics and its implication on elemental cycling in the aquatic environment

Battulga, B.; Nakayama, Masataka; Atarashi-Andoh, Mariko; Koarashi, Jun

no journal, , 

A growing attention has been addressed on microbial attachment and biofilm formation on plastic debris especially on microplastics (MPs; sizes: $$<$$5 mm) in the aquatic environment. The current study is focused on bacterial and fungal community composition, diversity, and structure in MP-associated biofilms to emphasize potential alteration of elemental cycling by the presence of MPs in the coastal aquatic environment. We collected MP, surface water, bottom sediment, and coastal sand samples from two contrasting coastal areas of Japan on a seasonal basis. Surface morphology and attached microorganisms on MPs were visually inspected by scanning electron microscopy (SEM). A high-throughput sequencing using Illumina MiSeq was performed in the collected samples to investigate the microbial community composition and diversity among different samples.

Oral presentation

Characterizing the plastic-associated biofilms by a multi-isotope approach; Insight from visible plastics in two contrasting coastal areas of Japan

Battulga, B.; Nakanishi, Takahiro; Atarashi-Andoh, Mariko; Koarashi, Jun

no journal, , 

Plastic debris in the aquatic environment receives special attention from scientific communities, whereas the radioactivity of environmental plastic and the dynamics of plastic-associated biofilm remain largely unknown. In this study, we addressed plastic-associated biofilms and bottom sediments from two contrasting coastal areas of Japan to elucidate their characteristics and interaction with radionuclides especially radiocesium ($$^{137}$$Cs) in the environment. We also explored stable isotope ($$^{13}$$C and $$^{15}$$N) signatures of the biofilm and sediment samples based on seasonal variations. Trace of $$^{137}$$Cs was observed in biofilm with an activity concentration of 292$$pm$$19.4 Bq kg$$^{-1}$$ biofilm (dw) which correspond to 1.15$$pm$$0.08 Bq kg$$^{-1}$$ plastic (dw).

Oral presentation

Occurrence of plastics and their association with radiocesium in the coastal rivers in Fukushima, Japan

Battulga, B.; Nakanishi, Takahiro; Atarashi-Andoh, Mariko; Koarashi, Jun

no journal, , 

Plastic debris is pervasive and persistent which allows its interaction with a range of organisms and organic and inorganic materials in the environment. Considering that plastics are considered carriers and vectors for pollutants in the aquatic environment, it is of utmost importance to elucidate the interaction between plastic debris and radionuclides. Because the accident at the Fukushima Daiichi Nuclear Power Plant caused by the Great East Japan Earthquake in 2011 led to the release of fission products, in particular radiocesium ($$^{137}$$Cs), into the environment, we aimed to elucidate the interaction between plastic debris and $$^{137}$$Cs in the environment. We selected the Kuma, Ukedo, Odaka, and Ohta Rivers of the Fukushima prefecture to collect environmental plastic and sediment samples. In addition, we adopted a newly developed ultrasound-assisted extraction technique to extract biofilm (a thin but robust layer of microbial cells embedded in an extracellular matrix) from plastics. The $$^{137}$$Cs activity concentrations in plastic-associated biofilms and river bottom sediments were determined by gamma-ray spectrometry. Our results indicate the dominance of common polymer types (i.e., polyethylene, polypropylene, polystyrene) of plastic debris in the river environments. Preliminary results of $$^{137}$$Cs analysis revealed that plastics serve as carriers for radionuclides mediated by biofilms in the coastal rivers.

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