Department of Biological Sciences, University of Wisconsin-Milwaukee, Milwaukee, WI 53211, USA.
Water Res. 2012 May 15;46(8):2615-26. doi: 10.1016/j.watres.2012.02.027. Epub 2012 Feb 24.
Chlorophyll a fluorescence of microalgae is a compelling indicator of toxicity of dissolved water contaminants, because it is easily measured and responds rapidly. While different chl a fluorescence parameters have been examined, most studies have focused on single species and/or a narrow range of toxins. We assessed the utility of one chl a fluorescence parameter, the maximum quantum yield of PSII (F(v)/F(m)), for detecting effects of nine environmental pollutants from a range of toxin classes on 5 commonly found freshwater algal species, as well as the USEPA model species, Pseudokirchneriella subcapitata. F(v)/F(m) declined rapidly over <20 min in response to low concentrations of photosynthesis-specific herbicides Diuron(®) and metribuzin (both <40 nM), atrazine (<460 nM) and terbuthylazine (<400 nM). However, F(v)/F(m) also responded rapidly and in a dose-dependent way to toxins glyphosate (<90 μM), and KCN (<1 mM) which have modes of action not specific to photosynthesis. F(v)/F(m) was insensitive to 30-40 μM insecticides methyl parathion, carbofuran and malathion. Algal species varied in their sensitivity to toxins. No single species was the most sensitive to all nine toxins, but for six toxins to which algal F(v)/F(m) responded significantly, the model species P. subcapitata was less sensitive than other taxa. In terms of suppression of F(v)/F(m) within 80 min, patterns of concentration-dependence differed among toxins; most showed Michaelis-Menten saturation kinetics, with half-saturation constant (K(m)) values for the PSII inhibitors ranging from 0.14 μM for Diuron(®) to 6.6 μM for terbuthylazine, compared with a K(m) of 330 μM for KCN. Percent suppression of F(v)/F(m) by glyphosate increased exponentially with concentration. F(v)/F(m) provides a sensitive and easily-measured parameter for rapid and cost-effective detection of effects of many dissolved toxins. Field-portable fluorometers will facilitate field testing, however distinct responses between different species may complicate net F(v)/F(m) signal from a community.
微藻叶绿素 a 荧光是一种很有吸引力的溶解水污染物毒性指示剂，因为它易于测量且响应迅速。虽然已经研究了不同的叶绿素 a 荧光参数，但大多数研究都集中在单一物种和/或毒素的狭窄范围内。我们评估了叶绿素 a 荧光参数之一 PSII 最大量子产量（F(v)/F(m)）的实用性，以检测来自多种毒素类别的九种环境污染物对 5 种常见淡水藻类物种以及美国环保署模式物种 Pseudokirchneriella subcapitata 的影响。F(v)/F(m)在不到 20 分钟的时间内，对低浓度的光合作用特异性除草剂 Diuron(®)和 metribuzin（均 <40 nM）、莠去津（<460 nM）和特丁津（<400 nM）迅速下降。然而，F(v)/F(m)也对非光合作用特异性作用模式的毒素草甘膦（<90 μM）和 KCN（<1 mM）快速且呈剂量依赖性地做出响应。F(v)/F(m)对 30-40 μM 的杀虫剂甲基对硫磷、克百威和马拉硫磷不敏感。藻类物种对毒素的敏感性不同。没有一种单一物种对所有九种毒素都最敏感，但对于六种对藻类 F(v)/F(m)有明显响应的毒素，模式物种 P. subcapitata 比其他类群更不敏感。在 80 分钟内 F(v)/F(m)抑制的浓度依赖性方面，毒素之间的模式存在差异；大多数毒素表现出米氏-门肯动力学，PSII 抑制剂的半饱和常数（K(m)）值范围从 Diuron(®)的 0.14 μM 到特丁津的 6.6 μM，而 KCN 的 K(m)为 330 μM。草甘膦对 F(v)/F(m)的抑制百分比随浓度呈指数增加。F(v)/F(m)为快速、经济有效地检测许多溶解毒素的影响提供了一个敏感且易于测量的参数。便携式荧光计将促进现场测试，然而不同物种之间的明显差异可能会使群落的净 F(v)/F(m)信号复杂化。
