Baxter Leilan, Brain Richard A, Lissemore Linda, Solomon Keith R, Hanson Mark L, Prosser Ryan S
School of Environmental Sciences, University of Guelph, Guelph, Ontario, Canada.
Syngenta Crop Protection LLC, Greensboro, NC, USA.
Ecotoxicol Environ Saf. 2016 Oct;132:250-9. doi: 10.1016/j.ecoenv.2016.06.022. Epub 2016 Jun 21.
The acute toxicity of herbicides to algae is commonly assessed under conditions (e.g., light intensity, water temperature, concentration of nutrients, pH) prescribed by standard test protocols. However, the observed toxicity may vary with changes in one or more of these parameters. This study examined variation in toxicity of the herbicide atrazine to a representative green algal species Raphidocelis subcapitata (formerly Pseudokirchneriella subcapitata) with changes in light intensity, water temperature, concentrations of nutrients or combinations of these three parameters. Conditions were chosen that could be representative of the intensive corn growing Midwestern region of the United States of America where atrazine is used extensively. Varying light intensity (4-58µmol/m(2)s) resulted in no observable trend in 96-h EC50 values for growth rate. EC50 values for PSII yield generally increased with decreasing light intensity but not significantly in all cases. The 96-h EC50 values for growth rate decreased with decreases in temperature (20-5°C) from standard conditions (25°C), but EC50 values for PSII yield at lower temperatures were not significantly different from standard conditions. Finally, there was no clear trend in 96-h EC50 values for both endpoints with increases in nitrogen (4.1-20mg/L) and phosphorus (0.24-1.2mg/L). The 96-h EC50 values for both endpoints under combinations of conditions mimicking aquatic systems in the Midwestern U.S. were not significantly different from EC50 values generated under standard test conditions. This combination of decreased light intensity and temperature and increased nutrients relative to standard conditions does not appear to significantly affect the observed toxicity of atrazine to R. subcapitata. For atrazine specifically, and for perhaps other herbicides, this means current laboratory protocols are useful for extrapolating to effects on algae under realistic environmental conditions.
除草剂对藻类的急性毒性通常在标准测试方案规定的条件下（如光照强度、水温、营养物质浓度、pH值）进行评估。然而，观察到的毒性可能会随着这些参数中的一个或多个的变化而有所不同。本研究考察了除草剂阿特拉津对代表性绿藻物种头状突尾藻（原名小形假蹄形藻）的毒性随光照强度、水温、营养物质浓度或这三个参数组合的变化情况。所选择的条件能够代表美国中西部玉米种植密集区的情况，在该地区阿特拉津被广泛使用。光照强度变化（4 - 58μmol/m²·s）对96小时生长率的半数有效浓度（EC50）值未产生明显趋势。PSII产量的EC50值一般随光照强度降低而增加，但并非在所有情况下都显著。与标准条件（25°C）相比，生长率的96小时EC50值随温度降低（20 - 5°C）而降低，但较低温度下PSII产量的EC50值与标准条件下无显著差异。最后，随着氮（4.1 - 20mg/L）和磷（0.24 - 1.2mg/L）含量增加，两个终点的96小时EC50值均无明显趋势。模拟美国中西部水生系统条件组合下两个终点的96小时EC50值与标准测试条件下产生的EC50值无显著差异。相对于标准条件，光照强度和温度降低以及营养物质增加的这种组合似乎并未显著影响观察到的阿特拉津对头状突尾藻的毒性。具体对于阿特拉津，也许对于其他除草剂也是如此，这意味着当前的实验室方案对于推断在实际环境条件下对藻类的影响是有用的。
