• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.19 no.1
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• pp.88-98
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• 2014

Despite of emerging and increasing concerns to microplastics, no standard methodology has not been proposed for determination of microplastics. This study aims to develop the analysis method for microplastics in seawater by overviewing methodologies proposed by previous studies and by assessing some processes in those methodologies which possibly cause uncertainties in microplastic determination. Furthermore, we present preliminary results of distribution characteristics of microplastics in seawater of Incheon/Kyeonggi coastal region which is based on our new methodology. Microplastics in surface microlayer (SML) and subsurface water (SSW) were collected using mesh screen and planktonic nets (trawl net with $330{\mu}m$ mesh size and hand net with $20{\mu}m$ mesh size), respectively. Microplastics with < $300{\mu}m$ was predominant, indicating hand net as the better collection tool for SSW. As for SML, FT-IR based microplastic concentration was well matched with naked-eye based concentration which has been used in most of previous studies. However, a poor relationship was observed for SSW, indicating that concentration data of previous SSW studies should be corrected. Incheon/Kyeonggi bay seawater contained the similar concentration range with those in coastal region of the Nakdong River. Our methodology can be used as a basic tool for further microplatic studies.

• Journal of Microbiology and Biotechnology
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• v.22 no.3
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• pp.283-291
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• 2012

Bioremediation efforts often rely on the application of surfactants to enhance hydrocarbon bioavailability. However, synthetic surfactants can sometimes be toxic to degrading microorganisms, thus reducing the clearance rate of the pollutant. Therefore, surfactant-resistant bacteria can be an important tool for bioremediation efforts of hydrophobic pollutants, circumventing the toxicity of synthetic surfactants that often delay microbial bioremediation of these contaminants. In this study, we screened a natural surfactant-rich compartment, the estuarine surface microlayer (SML), for cultivable surfactant-resistant bacteria using selective cultures of sodium dodecyl sulfate (SDS) and cetyl trimethylammonium bromide (CTAB). Resistance to surfactants was evaluated by colony counts in solid media amended with critical micelle concentrations (CMC) of either surfactants, in comparison with non-amended controls. Selective cultures for surfactant-resistant bacteria were prepared in mineral medium also containing CMC concentrations of either CTAB or SDS. The surfactantresistant isolates obtained were tested by PCR for the Pseudomonas genus marker gacA gene and for the naphthalene-dioxygenase-encoding gene ndo. Isolates were also screened for biosurfactant production by the atomized oil assay. A high proportion of culturable bacterioneuston was tolerant to CMC concentrations of SDS or CTAB. The gacA-targeted PCR revealed that 64% of the isolates were Pseudomonads. Biosurfactant production in solid medium was detected in 9.4% of tested isolates, all affiliated with genus Pseudomonas. This study shows that the SML is a potential source of surfactant-resistant and biosurfactant-producing bacteria in which Pseudomonads emerge as a relevant group.