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Tableau 3.1 Growth indicators (dry weight |pg ml¹], abundance [cclls ml^-1! and specific biovolume |mm³ ml'¹)) in an agricultural stream phytoplankton community after a 96 hours exposure to various conccntrations of glyphosatc-based herbicidc.

Glyphosate concentrations (pg I'¹)

	Control	1	5	10	50	100	500	1000
Dry weight	69.33^a	76.7^a	74. 7^a	84^a	62.7^a	73.3^a	41^B	34.6^U
	±14.7	±13.3	±16	±5.7	±4.2	±7	±4.2	±4.6
Abundance	2.3e+4^A	2.4e+4^A	2e+4^AB	2.4e+4^A.	1.6e+4"	1.7e+4^A	1.1 c+4^c	9.6e+3^c
	±l.5e+3	±1.1 e+3	±1.2e+3	±2.1e+3	±1.6e+3	±4.2e+3	±3.2e+3	±l.8e+3
Specific	3.3e-4^A	4e-4^A	4.4e-4^A	3.9e-4^A	4.3e-4^A	3.3e-4^A	8.1 e-5 ^B	3.3e-5 ^B
Biovolume	±8. le-4	±l.2e-3	± 1.1 e-3	±I.3e-3	±1.5e-3	±le-3	±l.6e-4	±4.9e-5

Trcatments means from ANOVA (n=3). Different Ietters in the same linę represents significant differcnces (p < 0.05) by the paired T-tcst.

3.6.3 Pigment content

Chlorophyll a content (% of pigment compared to control) significantly decreascd for phytoplankton cells cxposed to glyphosate concentrations of 1, 5, 100, 500 and 1000 pg I*¹ (table 3.2). There was no significant diffcrence between the intermediary (10 and 50 pg I*¹) and the control treatments. The chlorophyll b content showed no significant differences when compared to control. Concerning the carotenoid content, there was a significant decrcase of carotenoids for all glyphosate concentrations.

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