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States (Scribner et al_y 2007; Struger et al, 2008; Giroux and Pelletier, 2012). Phytoplankton samples were then placed in an environmental growth chamber (MTR30, Conviron, Manitoba, Canada) under similar temperaturę and light conditions than the ones observed the day before the sampling day (light dark cycle of 16:8 and averaged temperaturę of 15°C), and agitated manually twice daily (determined with a Hobo temp probe and data logger (Onsct, Massachusett, United States)). The sampling was done after 96 hours of exposure to glyphosate-based herbicide.

To determine glyphosate concentrations originally prcsent in the collected water, cnzyme linked immunosorbent assay (ELISA) (Abraxi$ LLC, Warminster, Pennsylvania, USA) was performed, with detection limit of0.05 pg L'¹.

3.5.2 Physiological features

After 96 hours of exposure, the samples from each Erlenmeyer łlask were divided into 50 ml Falcon tubes, then frozen at-20°C until physiological measurements. For each measurements, 50 ml of water was Filtered using glass microfiber filters grade GF/F: 0.8 pm (OWhatman Ltd.) and the evaluations were madę from biomass collected on Filters. Dry weight (pg ml*¹) was performed following Ameel et al. (1998), with 50 ml samples becn flltrated on rinsed and dried Filters, and dricd to a constant weight at 103-105°C. The pigments were extractcd in methanol. Chlorophyll a, b and carotenoids content was performed following Wellbum (1994) spectrophotometric method, expressed in % of pigment compared to control and calculated as:

Chlorophyll a - 15.65/1666-7.34/i₆₅₃    (3.1 )

Chlorophyll b - 27.05/*₆₅₃ - 11.2 M₆₆₆    (3.2)

Carotenoids = (1000/1470 - 2.86 Chlorophyll a- 129.2 Chlorophyll b) / 221    (3.3)

were A = Absorbance, calculated at 666, 653 and 470 nm