Response to variable light intensity in photoacclimated algae and cyanobacteria exposed to atrazine

详细信息    查看全文

• 作者：Charles P. Deblois ; Karine Dufresne ; Philippe Juneau ; ^{juneau.philippe@uqam.ca}
• 关键词：AI ; actinic light intensity ; RLC ; rapid light curve ; EC50 ; concentration causing 50 % of effect ; ET0· ; TR0&minus ; 1 (¦·0) ; PSII transfer efficiency beyond QA ; ETR ; electron transport rate ; HL ; high-light adapted ; LL ; low-light adapted ; NPQ ; non-photoch
• 刊名：Aquatic Toxicology
• 出版年：2013
• 出版时间：15 January, 2013
• 年：2013
• 卷：126
• 期：Complete
• 页码：77-84
• 全文大小：913 K

文摘

Atrazine is frequently detected in freshwater ecosystems exposed to agricultural waste waters and runoffs worldwide and it can affect non-target organisms (mainly photoautotrophic) and modify community structure. Meanwhile, light environment is known to vary between aquatic ecosystems, but also before and during the exposure to atrazine and these variations may modify the sensitivity to atrazine of photoautotroph organisms. In this study, 10 species of phytoplankton (chlorophytes, baccilariophytes and cyanophytes) acclimated to low or high light intensities were exposed to atrazine and light of different intensities to compare their combined effect. Our data showed that chlorophytes and baccilariophytes were more resistant to atrazine compared to cyanophytes for all light conditions. Atrazine was found to inhibit , ¦·₀, P_M and non-photochemical quenching for all species indicating an effect on electron transport, primary production and photoregulation processes. These data also indicate a higher sensitivity of ¦·₀ (average ¦·₀-EC₅₀ of 91 ¡À 11 nM or 19.6 ¡À 0.9 ¦Ìg L^?1) compared to (average of 217 ¡À 19 nM or 46.8 ¡À 4.1 ¦Ìg L^?1) and suggest that photoregulation processes activated in presence of light decrease the effect of atrazine. We also showed that increasing light intensity decreased in both low (except baccilariophytes) and high light acclimated conditions. Despite this similarity, most species acclimated to high light were found to have higher or similar compared to low light acclimated cells and thus, were less sensitive to atrazine in low light and high light environments. We concluded that an increase in the plastoquinone pool induced by acclimation to high light decreased the sensitivity to atrazine in phytoplankton and we hypothesized that the effect observed was the result of a dilution of atrazine toxicity through increased binding site availability (quinones) combined with increased photoregulation processes capacity.