Sensitivity of Scenedesmus obliquus and Microcystis aeruginosa to atrazine: effects of acclimation and mixed cultures, and their removal ability.
Atrazine is an herbicide frequently detected in watercourses that can affect the phytoplankton community, thus impacting the whole food chain. This study aims, firstly, to measure the sensitivity of monocultures of the green alga Scenedemus obliquus and toxic and non-toxic strains of the cyanobacteria Microcystis aeruginosa before, during and after a 30-day acclimation period to 0.1 µM of atrazine. Secondly, the sensitivity of S. obliquus and M. aeruginosa to atrazine in mixed cultures was evaluated. Finally, the ability of these strains to remove atrazine from the media was measured. We demonstrated that both strains of M. aeruginosa had higher growth rate-based EC50values than S. obliquus when exposed to atrazine, even though their photosynthesis-based EC50values were lower. After being exposed to 0.1 µM of atrazine for 1 month, only the photosynthesis-based EC50of S. obliquus increased significantly. In mixed cultures, the growth rate of the non-toxic strain of M. aeruginosa was higher than S. obliquus at high concentrations of atrazine, resulting in a ratio of M. aeruginosa to total cell count of 0.6. This lower sensitivity might be related to the higher growth rate of cyanobacteria at low light intensity. Finally, a negligible fraction of atrazine was removed from the culture media by S. obliquus or M. aeruginosa over 6 days. These results bring new insights on the acclimation of some phytoplankton species to atrazine and its effect on the competition between S. obliquus and M. aeruginosa in mixed cultures.
Department of Biological Sciences-GRIL-TOXEN, Ecotoxicology of Aquatic Microorganisms Laboratory, Université du Québec à Montréal, C.P. 8888, Succursale Centre-Ville, Montréal, QC, H3C 3P8, Canada.
Annie
A
Chalifour
Department of Chemistry, Bioanalytical Mass Spectrometry Laboratory, Université du Québec à Montréal, C.P. 8888, Succursale Centre-Ville, Montréal, QC, H3C 3P8, Canada.
André
A
LeBlanc
Department of Chemistry, Bioanalytical Mass Spectrometry Laboratory, Université du Québec à Montréal, C.P. 8888, Succursale Centre-Ville, Montréal, QC, H3C 3P8, Canada.
Lekha
L
Sleno
Department of Biological Sciences-GRIL-TOXEN, Ecotoxicology of Aquatic Microorganisms Laboratory, Université du Québec à Montréal, C.P. 8888, Succursale Centre-Ville, Montréal, QC, H3C 3P8, Canada. juneau.philippe@uqam.ca.
Philippe
P
Juneau
D000064:Acclimatization; D001280:Atrazine / Q000378:metabolism / Q000633:toxicity*; D001673:Biodegradation, Environmental; D006540:Herbicides; D046931:Microcystis / Q000187:drug effects* / Q000502:physiology; D010788:Photosynthesis; D010839:Phytoplankton / Q000187:drug effects; D044444:Scenedesmus / Q000187:drug effects* / Q000502:physiology; D014874:Water Pollutants, Chemical / Q000378:metabolism / Q000633:toxicity*
D006540:Herbicides; D014874:Water Pollutants, Chemical; D001280:Atrazine
Herbicide; Long-term exposure; Mixed cultures; Phytoplankton; Removal ability
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