Mohammed Muwafq H, Markert Bernd
Department of Biology, University of Baghdad, POB 60014, Baghdad, Iraq.
Environ Sci Pollut Res Int. 2006 Mar;13(2):98-104. doi: 10.1065/espr2005.07.274.
Aquatic environments are often exposed to various pollutants like heavy metals that are released from industrial, agricultural and domestic wastes. Emissions of heavy metals can then enter all ecosystems and bring about severe problems in plants, especially algae depending on the concentrations of a given element. The objective of the investigation presented is to detect toxic effects due to some heavy metals in the biomass of green alga Scenedesmus quadricauda.
All experiments were conducted with axenic cultures of the green alga Scenedesmus quadricauda (Turp.) de Brebisson (Chlorococcales, Chlorophyta). The cultures were grown in Chu-no.10 medium, and optimum physical and chemical growth conditions were provided to get higher growth rates and lower doubling times of cells. Growth of the micro algal cultures was measured on a daily schedule by counting cultures and determination of chlorophyll-a. The sterile-filtered heavy metal concentration solutions (Cd, Pb and Cu) were prepared and added as stock solutions of their salts (CdCl22.5 H2O, Pb(NO3)2H2O and CuSO4*5 H2O).
The growth decreased gradually with the alga exposed to Cd at 0.05, 0.1, and 0.5 mg/L in comparison with the control whereas 1 mg/L Cd2+ had a clearly destructive effect. The growth was decreased with Pb at 15, 20 and 25 mg/L gradually, while at 30 mg/L the effect was more pronounced. When Cu was used, the growth was increased gradually at 0.5, 1 and 1.5 mg/L and vice versa at 2 mg/L.
There were differences in toxic effects of the metals with different metal as well as their concentrations and the time of exposure.
水生环境常常受到各种污染物的影响，如来自工业、农业和生活废弃物释放的重金属。重金属排放随后可进入所有生态系统，并在植物中引发严重问题，尤其是藻类，这取决于特定元素的浓度。本研究的目的是检测某些重金属对绿藻四角栅藻生物量的毒性作用。
所有实验均使用绿藻四角栅藻（Turp.）de Brebisson（绿球藻目，绿藻门）的无菌培养物进行。培养物在朱氏10号培养基中生长，并提供最佳的物理和化学生长条件，以获得更高的生长速率和更低的细胞倍增时间。通过对培养物进行计数和测定叶绿素a，每日监测微藻培养物的生长情况。制备无菌过滤的重金属浓缩溶液（镉、铅和铜），并作为其盐的储备溶液添加（CdCl2·2.5H2O、Pb(NO3)2·H2O和CuSO4·5H2O）。
与对照组相比，当绿藻暴露于浓度为0.05、0.1和0.5mg/L的镉时，其生长逐渐下降，而1mg/L的Cd2+具有明显的破坏作用。当铅浓度为15、20和25mg/L时，生长逐渐下降，而在30mg/L时，影响更为明显。使用铜时，在0.5、1和1.5mg/L时生长逐渐增加，而在2mg/L时则相反。
不同金属及其浓度和暴露时间的毒性作用存在差异。
