Ecosistemas 29(3):2069 [Septiembre-Diciembre 2020] https://doi.org/10.7818/ECOS.2069 ecosistemasREVISTA CIENTÍFICA DE ECOLOGÍA Y MEDIO AMBIENTE aeet MONOGRÁFICO: ISSN 1697-2473 ASOCIACIÓN ESPAÑOLA Plásticos en ecosistemas acuáticos: presencia, transporte y efectos Open access / CC BY-NC 3.0 DE ECOLOGÍA TERRESTRE Editores: Gissell Lacerot, Juan Pablo Lozoya y Franco Teixeira de Mello disponible en www.revistaecosistemas.net Study of the plastisphere: biofilm development and presence of faecal indicator bacteria on microplastics from the Río de la Plata estuary R. S. Pazos1,2,*, J. C. Suárez1,2, N. Gómez1,2 (1) Instituto de Limnología ‘‘Dr. Raúl A. Ringuelet”, UNLP-CONICET (CCT La Plata), CC 712, 1900 La Plata, Argentina. (2) Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Argentina. * Autor de correspondencia: R. Soledad Pazos [[email protected]] > Recibido el 10 de agosto de 2020 - Aceptado el 16 de septiembre de 2020 Pazos, R.S., Suárez, J.C., Gómez, N. 2020. Study of the plastisphere: biofilm development and presence of faecal indicator bacteria on mi- croplastics from the Río de la Plata estuary. Ecosistemas 29(3): 2069. https://doi.org/10.7818/ECOS.2069 Microplastics (MPs) are considered emerging pollutants and often enter aquatic ecosystems carried by currents and tides until they accumulate on the shorelines. In many cases they may be colonized by diverse microorganisms forming a community called plastisphere, which can even act as a reservoir for pathogenic microorganisms. This study carried out in the Río de la Plata estuary (southern coastal fringe, Argentina) focused on two main objectives, the analysis of the biofilm colonizing MPs under laboratory conditions, and the detection of bacteria indicating faecal contamination (Escherichia coli and Enterococci), in MPs from the intertidal sediment at coastal sites with different land uses, in the freshwater sector of the Río de la Plata estuary. The colonization experiment was carried out in the laboratory with water from the estuary for a period of 35 days (residence time of the water in the freshwater sector of the estuary). The results revealed a remarkable development and diversity of biofilm organisms from the second week of colonization on, covering the surface of the microplastic and thus masking this pollutant. On the other hand, the presence of faecal indicator bacteria in the MPs of the intertidal sediment was confirmed in all the studied sites, being proportionally higher on MPs found in areas influenced by sewage discharges Keywords: contaminants; plastics; colonization; Escherichia coli Pazos, R.S., Suárez, J.C., Gómez, N. 2020. Estudio de la plastisfera: desarrollo del biofilm y presencia de bacterias indicadoras fecales en microplásticos del estuario del Río de la Plata. Ecosistemas 29(3): 2069. https://doi.org/10.7818/ECOS.2069 Los microplásticos (MPs) son considerados contaminantes emergentes y suelen ingresar en los ecosistemas acuáticos donde son transportados por las corrientes y mareas hasta acumularse en las costas. En muchos casos éstos pueden ser colonizados por diversos microorganismos confor- mando una comunidad denominada plastisfera y hasta pueden actuar como reservorio de microorganismos patógenos. En el estuario del Río de la Plata (Franja Costera Sur, Argentina), se realizó un estudio cuyo objetivo fue analizar el biofilm que se desarrolla sobre MPs en condiciones de la- boratorio y analizar la presencia de bacterias indicadoras de contaminación fecal (Escherichia coli y Enterococos) en MPs hallados en el sedimento intermareal en sitios costeros con diferentes usos del suelo, en el sector de agua dulce del estuario del Río de la Plata. La experiencia de colonización se realizó en laboratorio con agua procedente del estuario durante un período de 35 días (tiempo de residencia del agua en el sector de agua dulce del estuario). Los resultados revelaron un notable desarrollo y diversidad de organismos del biofilm a partir de la segunda semana de colonización, recubriendo la superficie del microplástico y enmascarando así a este contaminante. Por otra parte, se confirmó la presencia de bacterias indicadoras fecales en los MPs del sedimento intermareal en todos los sitios estudiados, siendo proporcionalmente mayor en los MPs hallados en áreas influen- ciadas por descargas cloacales. Palabras clave: contaminantes; plásticos; colonización; Escherichia coli Introduction tants, microplastic surfaces can be colonized by microbial commu- nities, that form a biofilm (Zettler et al. 2013; McCormick et al. 2014; Currently, plastic contamination is a matter of great concern Oberbeckmann et al. 2014; De Tender et al. 2015; Hoellein et al. since they have reached a volume of approximately 8 million tons 2017; Dussud et al. 2018). The biofilm developed on plastic is called per year in the oceans (Rodrigues, Duarte, et al. 2019). A particular “plastisphere” (Zettler et al. 2013) and that surface represent a dif- type of contaminant within plastic litter is microplastics (MPs), which ferent habitat for the development of the microbial community. are pieces smaller than 5 mm (Arthur et al. 2009), defined as a het- The biofilms that colonize plastic exposed to the marine environ- erogeneous mixture of differently shaped materials (EFSA 2016), ment are mainly modulated by biogeographic and environmental fac- and considered by the United Nations Environment Program as one tors, such as salinity and the concentration of nutrients in the water of the 10 emerging problems, because they are widely distributed (Amaral-Zettler et al. 2015; Oberbeckmann et al. 2018). Microplastic in many ecosystems around the world (Lithner 2011). surfaces themselves also influence colonization processes, since Once inside ecosystems, organisms interact with MPs, being some organisms in the plastisphere could use plastic as an energy able to ingest them or colonize their surfaces. In the latter case, source due to their ability to degrade highly complex biopolymers MPs in aquatic environments can serve as substrates for various such as lignin and petroleum derivatives (Zettler et al. 2013; Ober- microorganisms, that is, in addition to accumulating organic pollu- beckmann et al. 2016; Ogonowski et al. 2018). © 2020 Los Autores. Editado por la AEET. [Ecosistemas no se hace responsable del uso indebido de material sujeto a derecho de autor] 1 Ecosistemas 29(3) : 2069 Pazos et al. 2020 Recently, the potential danger of microbial communities asso - S, 58° 13’ 48” W and 35° 16´ 37” S, 57° 13´ 26” W), exposed to dif - ciated with MPs has begun to be studied, since the role of MPs as ferent land uses ( Gómez and Cochero 2013 ). In Quilmes site (QUI), carriers of antibiotic resistance genes has been discussed ( Arias- recreational and fishing activities are carried out. It is exposed to Andres et al. 2018 ). These authors analysed the permissiveness the impact of the city of Buenos Aires, and downstream the dis - of aquatic bacteria towards a model antibiotic resistance plasmid, charge from a highly polluted basin such as the Matanza-Riachuelo comparing the organisms of biofilms on MPs vs. those that are River. Berazategui site (BE) is located near the sewage effluent of free-living. They observed that a horizontal gene transfer in this the city of Buenos Aires, and Punta Colorada site (PC) is located habitat could distinctly affect the ecology of aquatic microbial com - downstream. In Punta Lara site (PL) mostly recreational and fishing munities on a global scale. In addition to the role of MPs as carriers activities are carried out. Bagliardi site (BAG) is located in the area of antibiotic resistance genes, they could act as vectors that favour surrounding the sewage effluent of the city of La Plata, and Balan - the distribution of possible pathogen agents from areas of waste - dra site (BAL) is located downstream. The southernmost site of the water discharge to aquatic ecosystems not affected by such con - study area is Punta Indio (PI), which is the closest to the Maximum tamination ( Oberbeckmann et al. 2015 ). Pathogens such as Turbidity Front of the estuary with salinity close to 10 PSU ( Licursi members of the genus Vibrio , have been reported as abundant on et al. 2010 ). MPs ( Zettler et al. 2013 ; Frère et al. 2018 ). Likewise, the biofilm that colonizes the surface of the MPs could act as a reservoir for Laboratory experiment indicators of faecal contamination, such as Escherichia coli . There - To analyse the colonization of the biofilm on MPs under labora - fore, it is essential to better understand the potential of MPs to fa - tory conditions, water was extracted from the PL site, and refriger - cilitate the survival of these organisms and, therefore, to increase ated during its transport to the laboratory. Before starting the exposure routes in humans by providing a vehicle for dispersal in bioassay, all the materials were autoclaved. Eighteen glass jars with coastal waters ( Rodrigues, Oliver, et al. 2019 ). 60 ml of water from the sampling site were used, adding 20 spherical Most papers on plastisphere are focused on marine environ - MPs (size: 3 mm, polymer: PE (polyethylene), color: pink and white) ments, but it is important to study them in estuarine ecosystems to each of them. The jars were placed in a shaker with a rotary due to the services provided by these environments as well as to movement at 150 mot min -1 under laboratory conditions (mean tem - the large load of contaminants that reach their coasts. Specifically, perature 20º C, average light intensity of 790 µM m 2s-1 ). The water in South America, most of them suffer the consequences of urban was partially renewed once a week and the duration of the bioassay and industrial centres settled on their margins, the expansion of was 35 days, considering the residence time of the water in the agriculture and aquaculture, water extraction, wastewater dis - freshwater sector of the estuary ( FREPLATA 2005 ). For biofilm charge, and the entry of various contaminants, among which are analysis, samples were extracted in triplicate on days 2, 7, 14, 21, the MPs ( Barletta et al.