Synergistic effects of elevated carbon dioxide and sodium hypochlorite on survival and impairment of three phytoplankton species

doi:2013.28.2.173

Algae > Volume 28(2); 2013 > Article

Algae 2013;28(2): 173-183. doi: https://doi.org/10.4490/algae.2013.28.2.173

Keunyong Kim¹, Kwang Young Kim¹^,*, Ju-Hyoung Kim¹, Eun Ju Kang¹, Hae Jin Jeong² and Kitack Lee³

¹Department of Oceanography, College of Natural Sciences, Chonnam National University, Gwangju 500-757, Korea
²School of Earth and Environmental Sciences, College of Natural Sciences, Seoul National University, Seoul 151-747, Korea
³School of Environmental Science and Engineering, Pohang University of Science and Technology, Pohang 790-784, Korea

*Corresponding Author

Email: kykim@chonnam.ac.kr

ABSTRACT

Sodium hypochlorite (NaOCl) is widely used to disinfect seawater in power plant cooling systems in order to reduce biofouling, and in ballast water treatment systems to prevent transport of exotic marine species. While the toxicity of NaOCl is expected to increase by ongoing ocean acidification, and many experimental studies have shown how algal calcification, photosynthesis and growth respond to ocean acidification, no studies have investigated the relationship between NaOCl toxicity and increased CO2. Therefore, we investigated whether the impacts of NaOCl on survival, chlorophyll a (Chl-a), and effective quantum yield in three marine phytoplankton belonging to different taxonomic classes are increased under high CO2 levels. Our results show that all biological parameters of the three species decreased under increasing NaOCl concentration, but increasing CO2 concentration alone (from 450 to 715 μatm) had no effect on any of these parameters in the organisms. However, due to the synergistic effects between NaOCl and CO2, the survival and Chl-a content in two of the species, Thalassiosira eccentrica and Heterosigma akashiwo, were significantly reduced under high CO2 when NaOCl was also elevated. The results show that combined exposure to high CO2 and NaOCl results in increasing toxicity of NaOCl in some marine phytoplankton. Consequently, greater caution with use of NaOCl will be required, as its use is widespread in coastal waters.

Key words: high CO2; marine phytoplankton; ocean acidification; sodium hypochlorite; synergistic effect