New findings on the effect of glyphosate on autotrophic and heterotrophic picoplankton structure: a microcosm approach

SABIO Y GARCÍA CARMEN; SCHIAFFINO, M.R.; LOZANO VERÓNICA; VERA, M.S.; FERRARO, M.; IZAGUIRRE, I.; PIZARRO, H

AQUATIC TOXICOLOGY

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2020

0166-445X

ABSTRACTMassive use of glyphosate in agricultural activities has led to the appearance ofthis herbicide in freshwater systems, which represents a potential threat tothese systems and their communities. This herbicide can directly affectautotrophic and heterotrophic picoplankton abundance. However, little is knownabout glyphosate impact on the whole structure of these assemblages. Herein,we used an 8-day long microcosm approach under indoor controlled conditionsto analyze changes in the structure of picoplankton exposed to a single pulse ofglyphosate. The analyzed picoplankton samples correspond to two outdoorponds with contrasting states: ?clear? (chlorophyll-a= 3.48 μg l-1 ± 1.15;nephelometric turbidity, NTU= 1) and ?turbid? (chlorophyll-a= 105.96 μg l-1 ±15.3; NTU= 48). The composition of the populations was analyzed through flowcytometry and the bacteria assemblages were further studied throughdenaturing gradient gel electrophoresis (DGGE) of 16s rRNA gene fragments.Cytometric populations of phycocyanin-rich picocyanobacteria drasticallydecreased in both systems when exposed to glyphosate. Alterations in thebacterial structure were also evident according to DGGE fingerprinting. Theseresults demonstrate that upon glyphosate exposure picoplanktonic fractionsface not only the already reported changes in abundance, but also alterations inthe composition of cytometric groups and of bacterial dominant operationaltaxonomic units. This research provides suitable and still little explored tools to analyze agrochemical effects on picoplanktonic communities