Please cite this article in press as: Qian, H., et al., Effects of copper sulfate, hydrogen peroxide and N-phenyl-2-naphthylamine on oxida- tive stress and the expression of genes involved photosynthesis and microcystin disposition in Microcystis aeruginosa. Aquat. Toxicol. (2010), doi:10.1016/j.aquatox.2010.05.018 ARTICLE IN PRESS G Model AQTOX-2816; No. of Pages 8 Aquatic Toxicology xxx (2010) xxx–xxx Contents lists available at ScienceDirect Aquatic Toxicology journal homepage: www.elsevier.com/locate/aquatox Effects of copper sulfate, hydrogen peroxide and N-phenyl-2-naphthylamine on oxidative stress and the expression of genes involved photosynthesis and microcystin disposition in Microcystis aeruginosa Haifeng Qian, Shuqiong Yu, Zhengqi Sun, Xiucai Xie, Weiping Liu, Zhengwei Fu ∗ College of Biological and Environmental Engineering, Zhejiang University of Technology, Hangzhou, Zhejiang, 310032, China article info Article history: Received 12 February 2010 Received in revised form 24 May 2010 Accepted 29 May 2010 Keywords: Microcystis aeruginosa Toxicity CuSO4 H2O2 PNA Gene transcription abstract Algal blooms have been increasing in prevalence all over the world, destroying ecosystems and plac- ing other organisms at risk. Chemical remediation is one of most important methods of controlling algal bloom formation. The effects of copper sulfate, hydrogen peroxide (H 2 O 2 ) and N-phenyl-2- naphthylamine on photosynthesis-related and microcystin-related gene transcription and physiological changes of Microcystis aeruginosa were analyzed. The results suggest that transcription of psaB, psbD1 and rbcL was inhibited by the three algaecides, which blocked the electron transport chain, significantly enhanced reactive oxygen species (ROS) accumulation and overwhelmed the antioxidant system. The increase in ROS destroyed pigment synthesis and membrane integrity, which inhibited or killed the algal cells. Furthermore, H 2 O 2 treatment down-regulated mcyD transcription, which indicated a decrease in the microcystin level in the cells. Our results demonstrate that H 2 O 2 has the greatest potential as an algaecide because it not only inhibits algae growth but may reduce microcystin synthesis. © 2010 Elsevier B.V. All rights reserved. 1. Introduction In recent decades, algal blooms have been occurring worldwide. In algal blooms, cyanobacteria are the most common group of algae, and they live in terrestrial, fresh, brackish or marine waters (Sinclair et al., 2008). These bacteria are usually too small to be seen, but when the cyanobacteria increase rapidly to form a bloom, the sur- face of the water becomes painted in colors of blue, bright green, brown or red. As algae of the cyanobacterial bloom die, the water can smell bad, which is a serious problem for drinking water sup- plies and recreational economic development. Within the algal blooms, some cyanobacteria can produce tox- ins (Sivonen and Jones, 1999) that pose a risk to human health and can affect fishing and aquaculture (Malbrouck and Kestemont, 2006). Microcystis aeruginosa is the most common toxin-producing cyanobacterium. It produces hepatotoxic microcystins, which are the main type of cyanobacterial toxin (Rinehart et al., 1994) and are responsible for liver disease (Carmichael, 2001) and even liver and colon cancer (Ueno et al., 1996; Humpage et al., 2000). Many methods for preventing blooms have been tested, including reducing nutrient input into water systems to pre- vent over-enrichment and altering the hydrophysical conditions ∗ Corresponding author. Tel.: +86 571 8832 0599; fax: +86 571 8832 0599. E-mail address: azwfu2003@yahoo.com.cn (Z. Fu). to allow the environment to favour other phytoplankton over the cyanobacteria (Hrudey et al., 1999). However, these meth- ods were not particularly successful. Chemical remediation utilizes chemical reagents to inhibit or kill algae, which may offer an alternative for bloom control (Barrington and Ghadouani, 2008). Copper sulfate (CuSO 4 ) is regarded as an economical, effective algaecide because it is considered to be generally safe for human health at the doses commonly used (WHO, 1996), while caus- ing aggregation of DNA fibrils, rupture of the thylakoids and cell death in algae (Verhoeven and Eloff, 1979). Hydrogen peroxide (H 2 O 2 ) is a strong oxidizing agent that is considered to be an effective and environmentally benign treatment for the inhibi- tion of cyanobacterial growth (Drábková et al., 2007; Barrington and Ghadouani, 2008) because it is a natural photochemical prod- uct formed in waters under sunlight and can be quickly degraded into oxygen and water (Cooper and Zika, 1983). N-phenyl-2- naphthylamine (PNA) is a secondary metabolite produced by plants (Sultankhodzhaev and Tadzhibaev, 1976; Sun et al., 1993) and is a strong anti-algal allelochemical (Qian et al., 2009). Allelopathic compounds are considered to be less polluting than traditional herbicides because they are degraded rapidly (Macías et al., 1998). The effects of potential algaecides on algae growth have been analyzed based on inhibition of algal growth (Nakai et al., 2000), pigment content and photosynthetic rate (Gouvêa et al., 2008), among other things. Recently, real-time PCR analy- sis has been applied to measure gene transcription during algal 0166-445X/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.aquatox.2010.05.018